Wednesday.
1409.8297
The effect of baryons on the inner density profiles of rich clusters
Schaller, Frenk, Bower, et al
Use the "Evolution and assembly of galaxies and their environment" (EAGLE) cosmo sim to investigate the effect of baryons on the density profiles of rich galaxy clusters. Focus on the 6 most massive EAGLE clusters (>1e14Msun) which can be compared with a recent analysis of 7 real clusters by Newman+. The central BCGs in EAGLE have steep stellar density profiles rho_*(r)~r^-3. Stars dominate the mass density for r<10 kpc, and, as a result, the total mass density profiles are steeper than the NFW profile. However, the DM halo itself closely follows the NFW form at all resolved radii (r>3.0 kpc). The EAGLE BCGs have similar surface brightness and LoS velocity dispersion profiles as the BCGs observed. The central slopes of the total mass profiles are also consistent with the observed clusters. However, after subtracting the contribution of the stars to the central density, Observation find significantly shallower slopes than NFW, in contradiction with EAGLE results. Discuss possible reasons for the discrepancy, such as differences in the mass of the simulated and observed clusters or orientation biases in the observed sample. Conclude that an inconsistency between the kinematical model adopted by observation for their BCGs, which assumes isotropic stellar orbits, and the kinematical structure of the EAGLE BCGs, in which the orbital stellar anisotropy varies with radius and tends to be radial biased, could explain at least par of the discrepancy.
1409.8562
Extending the supernova Hubble diagram to z~1.5 with the Euclid space mission
Astier et al
Forecast DE constraints that could be obtained from SNIa at high-z with Euclid. Simulate a 3-prong SN survey: z<0.35 (8000 SNe), 0.2<z<0.95 (8800 SNe), and 0.75<z<1.55 (1700 SNe) samples. The nearby and intermediate surveys are assumed to be conducted from the ground, while the high-z is a joint ground- and space-based survey. This latter survey, the DE SN IR experiment (DESIRE), is designed to fit within 6 months of Euclid observing time, with a dedicated observing program. Simulate the SN events as they would be observed in rolling-search mode by the various instruments, and derive the quality of expected cosmological constraints. Account for known systematic uncertainties, in particular calibration uncertainties including their contribution through the training of the SN model used to fit the SN light curves. Using conservative assumptions and 1d geometric Planck prior, find that the ensemble of surveys would yield competitive constraints: a constant EoS parameter can be constrained to sigma(w)=0.022, and DETF FoM of 203 is found for a 2-param EoS. Simulations thus indicate that Euclid can bring a significant contribution to a purely geometrical cosmo constraint by extending a high-quality SN Hubble diagram to z~1.5. Also present other science topics enabled by the DESIRE Euclid observations.
Tuesday, September 30, 2014
Day 754
Tuesday.
1409.7693
Clustering properties of moderate luminosity X-ray selected Type 1 and Type 2 AGN at z~3
Allevato et al
Type 1 and 2 COSMOS AGN at z=3 inhabit DM haloes with typical mass of log Mh=12.84 pm 0.1 and 11.73 pm 0.4, respectively. This result requires a drop in the halo masses of Type 1 and 2 COSMOS AGN at z~3 compared to z<2 XMM COSMOS AGN with similar luminosities. Additionally, we infer that unobscured COSMOS AGN at z~3 reside in 10x more massive haloes compared to obscured COSMOS AGN (2.6 sigma). The result extend to z~3 that found in COSMOS at z<1, and rules out the picture in which obscuration is purely an orientation effect. A model which assumes that the AGN activity is triggered by major mergers is quite successful in predicting both the low halo mass of COSMOS AGN and the typical mass of luminous SDSS quasars at z~3, which the latter inhabiting more massive haloes respect to moderate luminosity AGN. Alternatively, can argue at least for Type 1 COSMOS AGN, that they are possibly representative of an early phase of fast (Eddington limited) BH growth induced by cosmic cold flows or disk instabilities. Given the moderate luminosity, these new fast growing BHs have masses of e7-8 Msun at z~3 which might evolve into e8.5-9 Msun mass BHs at z=0. Following the clustering measurements, argue that this fast BH growth at z~3 in AGN with moderate luminosity occurs in DMHs with typical mass of 6e12 Msun/h.
1409.7701
The Norma Arm region Chandra survey: X-ray populations in the spiral arms
Fornasini et al
1415 X-ray sources in Norma arm, 1130 are point-like sources. Since most sources have too few counts to permit individual classification, they are divided into five spectral groups defined by their quantile properties. Analyze stacked spectra of X-ray sources within each group, in conjunction with their fluxes, variability ,and IR counterparts, to ID the dominant population in the survey. Find that ~50% of sources are FG sources located within 1-2 kpc, which is consistent with expectations from previous surveys. ~20% of sources are likely located in the proximity of the Scutum-Crux and near Norma arm, while 30% are more distant, in the proximity of the far Norma arm or beyond. Argue that a mixture of B and non-B CVs dominates the Scutum-Crux and near Norma arms, while intermediate polars and high-mass stars (isolated or in binaries) dominate the far Norma arm. Population of very hard sources in the vicinity of the far Norma arm and AGN dominate the hard X-ray emission, but the distribution curve flattens at fainter fluxes. Find good agreement between the observed distribution and predictions based on other surveys.
1409.7718
Comparing Planck and WMAP: maps, spectra, and parameters
Larson, Weiland, Hinshaw, Bennett
Examine the consistency of WMAP9 and Planck data. Compare sky maps, PS, and inferred LCDM cosmo parameters. Residual dipoles are seen in the WMAP and Planck sky map differences, but are consistent within the uncertainties and are not large enough to explain the widely-noted differences in angular PS at higher ell. After removing residual dipoles and galactic FG, the residual difference maps exhibit a quadrupole and other large-scale systematic structure. Identify this structure as possibly originating from Planck's beam side lobe pick-up, but note that it appears to have insignificant cosmological impact. Develop an extension of the internal linear combination technique and find features that plausibly originate in the Planck data. Examine LCDM model fits to the angular PS and conclude that at the ~2.5% difference in the spectra at multipoles greater than ell~100 are significant at the 3-5 sigma level. Revisit the analysis of WMAP's beam data and conclude that previously derived uncertainties are robust and cannot explain the PS differences. Finally, examine the consistency of the LCDM parameters inferred from each data set taking into account the fact that both experiments observe the same sky, but cover different multipole ranges, apply different sky masks, and have different noise. While individual parameter values agree within the uncertainties, the 6 parameters taken together are discrepant at the ~6 sigma level, with chi2=56 for 6 dof (PTE=3e-10). Of the 6 parameters, chi2 is best improved by marginalizing over Omega_c h^2, given chi2=5.2 for 5 degrees of freedom. Find that perturbing the WMAP window function by its dominant beam error profile has little effect on Omega_c h^2, while perturbing the Planck window function by its corresponding error profile has a much greater effect on Omega_c h^2.
1409.8246
Strong chromatic microlensing in HE0047-1756 and SDSS1155+6346
Rojas, et al
Use spectra of double lensed quasars to study their unresolved structure through microlensing. No strong evidence of ML except in Lya line in SDSS 1155, which show strong differences in the shapes for A and B images. (But the continuum of B image spectrum is strongly contaminated by the lens galaxy.) Using the flux ratios of the emission lines, detected strong chromatic ML in the continuum in both lens systems. Contrary to other lens systems, the chromaticity detected is large enough to fulfill the thin disk prediction. The inferred sizes, however, are very large compared to the predictions of this model.
1409.7693
Clustering properties of moderate luminosity X-ray selected Type 1 and Type 2 AGN at z~3
Allevato et al
Type 1 and 2 COSMOS AGN at z=3 inhabit DM haloes with typical mass of log Mh=12.84 pm 0.1 and 11.73 pm 0.4, respectively. This result requires a drop in the halo masses of Type 1 and 2 COSMOS AGN at z~3 compared to z<2 XMM COSMOS AGN with similar luminosities. Additionally, we infer that unobscured COSMOS AGN at z~3 reside in 10x more massive haloes compared to obscured COSMOS AGN (2.6 sigma). The result extend to z~3 that found in COSMOS at z<1, and rules out the picture in which obscuration is purely an orientation effect. A model which assumes that the AGN activity is triggered by major mergers is quite successful in predicting both the low halo mass of COSMOS AGN and the typical mass of luminous SDSS quasars at z~3, which the latter inhabiting more massive haloes respect to moderate luminosity AGN. Alternatively, can argue at least for Type 1 COSMOS AGN, that they are possibly representative of an early phase of fast (Eddington limited) BH growth induced by cosmic cold flows or disk instabilities. Given the moderate luminosity, these new fast growing BHs have masses of e7-8 Msun at z~3 which might evolve into e8.5-9 Msun mass BHs at z=0. Following the clustering measurements, argue that this fast BH growth at z~3 in AGN with moderate luminosity occurs in DMHs with typical mass of 6e12 Msun/h.
1409.7701
The Norma Arm region Chandra survey: X-ray populations in the spiral arms
Fornasini et al
1415 X-ray sources in Norma arm, 1130 are point-like sources. Since most sources have too few counts to permit individual classification, they are divided into five spectral groups defined by their quantile properties. Analyze stacked spectra of X-ray sources within each group, in conjunction with their fluxes, variability ,and IR counterparts, to ID the dominant population in the survey. Find that ~50% of sources are FG sources located within 1-2 kpc, which is consistent with expectations from previous surveys. ~20% of sources are likely located in the proximity of the Scutum-Crux and near Norma arm, while 30% are more distant, in the proximity of the far Norma arm or beyond. Argue that a mixture of B and non-B CVs dominates the Scutum-Crux and near Norma arms, while intermediate polars and high-mass stars (isolated or in binaries) dominate the far Norma arm. Population of very hard sources in the vicinity of the far Norma arm and AGN dominate the hard X-ray emission, but the distribution curve flattens at fainter fluxes. Find good agreement between the observed distribution and predictions based on other surveys.
1409.7718
Comparing Planck and WMAP: maps, spectra, and parameters
Larson, Weiland, Hinshaw, Bennett
Examine the consistency of WMAP9 and Planck data. Compare sky maps, PS, and inferred LCDM cosmo parameters. Residual dipoles are seen in the WMAP and Planck sky map differences, but are consistent within the uncertainties and are not large enough to explain the widely-noted differences in angular PS at higher ell. After removing residual dipoles and galactic FG, the residual difference maps exhibit a quadrupole and other large-scale systematic structure. Identify this structure as possibly originating from Planck's beam side lobe pick-up, but note that it appears to have insignificant cosmological impact. Develop an extension of the internal linear combination technique and find features that plausibly originate in the Planck data. Examine LCDM model fits to the angular PS and conclude that at the ~2.5% difference in the spectra at multipoles greater than ell~100 are significant at the 3-5 sigma level. Revisit the analysis of WMAP's beam data and conclude that previously derived uncertainties are robust and cannot explain the PS differences. Finally, examine the consistency of the LCDM parameters inferred from each data set taking into account the fact that both experiments observe the same sky, but cover different multipole ranges, apply different sky masks, and have different noise. While individual parameter values agree within the uncertainties, the 6 parameters taken together are discrepant at the ~6 sigma level, with chi2=56 for 6 dof (PTE=3e-10). Of the 6 parameters, chi2 is best improved by marginalizing over Omega_c h^2, given chi2=5.2 for 5 degrees of freedom. Find that perturbing the WMAP window function by its dominant beam error profile has little effect on Omega_c h^2, while perturbing the Planck window function by its corresponding error profile has a much greater effect on Omega_c h^2.
1409.8246
Strong chromatic microlensing in HE0047-1756 and SDSS1155+6346
Rojas, et al
Use spectra of double lensed quasars to study their unresolved structure through microlensing. No strong evidence of ML except in Lya line in SDSS 1155, which show strong differences in the shapes for A and B images. (But the continuum of B image spectrum is strongly contaminated by the lens galaxy.) Using the flux ratios of the emission lines, detected strong chromatic ML in the continuum in both lens systems. Contrary to other lens systems, the chromaticity detected is large enough to fulfill the thin disk prediction. The inferred sizes, however, are very large compared to the predictions of this model.
Sunday, September 28, 2014
Day 753
Sunday. Monday.
1409.1924
The re-distribution of matter in the cores of galaxy clusters
Laporte, White
Present cosmological N-body re-sims of the assembly of BCGs in rich clusters. At z=2 populate DM sub haloes with self-gravitating stellar systems whose abundance and structure match observed high-z galaxies. By z=0, mergers have built much larger galaxies at cluster center. Their DM density profiles are shallower than in corresponding DM only simulations, but their total mass density profiles (stars + DM) are quite similar. Differences are found only at radii where the effects of central BHs may be significant. DM density slopes shallower than gamma=1.0 occur for r/r_200 < 0.015, close to the half-light radii of the BCGs. Experiments support earlier suggestions that NFW-like profiles are an attractor for the hierarchical growth of structure in collision less systems -- total mass density profiles asymptote to the solution found in DM-only sims over the radial range where mergers produce significant mixing between stars and DM. Simulated DM fractions are substantially higher in BCGs than in field ellipticals, reaching 80% within the HLR. Also estimate that SMBH mergers should create BCG cores as large as r_c~3 kpc. The good agreement of all these properties with recent observational studies of BCG structure suggests that dissipation processes have not played a dominant role in the assembly of the observed systems.
1409.7389
Modeling the redshift-space three-point correlation function in SDSS-III
Guo et al
Present z-space 3PCF for z~0.5 CMASS LRGs in BOSS DR11. The 3PCF measurements are interpreted within the HOD framework using high-res N-body sims, and the model successfully reproduces the 3PCF on scales larger than 1 Mpc/h. As with the case for the z-space 2PCF, find that the z-space 3PCF measurements also require the inclusion of galaxy velocity bias in the model. In particular, the central galaxy in a halo on average is in motion wrt the core of the halo. Discuss the potential of the small-scale 3PCF to tighten the constraints on the relation between galaxies and DM haloes and on the phase-space distribution of galaxies.
1409.7395
GIZMO: a new class of accurate, mesh-free hydrodynamic simulation methods
Hopkins
Present and study 2 new Langrangian numerical methods for solving the equations of hydrodynamics, in a systematic comparison with moving-mesh, SPH, and non-moving grid methods. The new methods are designed to capture many advantages of both SPH and grid-based AMR schemes. They are based on a kernel discretization of the volume coupled to a high-order matrix gradient estimator and a Riemann solver acting over the volume 'overlap.' Implement and test a parallel, second-order version of the method with coupled self-gravity & cosmological integration, in the code GIZMO: this maintains exact mass, energy and momentum conservation; exhibits superior angular momentum conservation compared to all other methods studied; does not require 'artificial diffusion' terms; and allows fluid elements to move with the flow so resolution is automatically adaptive. Consider a large suite of test problems, and find that on all problems the new methods appear competitive with moving-mesh schemes, with some advantages (particularly in angular momentum conservation), at the cost of enhanced noise. The new methods have many advantages vs SPH: proper convergence, good capturing of fluid-mixing instabilities, dramatically reduced 'particle noise' & numerical viscosity, more accurate sub-sonic flow evolution, & numerical diffusion, velocity-independence of errors, accurate coupling to N-body gravity solvers, good angular momentum conservation, and elimination of 'grid alignment' effects. Can, for example, follow hundreds of orbits of gaseous disks, while AMR and SPH methods break down in a few orbits. All of these differences are important for a wide range of astrophysical problems.
1409.7398
The ancient heritage of water ice in the solar system
Cleeves et al
Identifying the source of Earth's water is central to understanding the origins of life-fostering environments and to assessing the prevalence of such environments in space. Water throughout the solar system exhibits D to H enrichments, a fossil relic of low-temperature, ion-derived chemistry within either (i) the parent molecular cloud or (ii) the solar nebular protoplanetary disk. Utilizing a comprehensive treatment of disk ionization, find that ion-driven D pathways are inefficient, curtailing the disk's D-water formation and its viability as the sole source for the SS's water. This finding implies that if the SS's formation was typical, abundant interstellar ices are available to all nascent planetary systems.
1409.7583
Representations of Time Coordinates in FITS
Rots et al
Time on all scales and precisions known in astronomical datasets is to be described in an unambiguous, complete, and self-consistent manner. Employing the well-established WCS framework, and maintaining compatibility with the FITS conventions that are currently in use to specify time, the standard is extended to describe rigorously the time coordinate. World coordinate functions are defined for temporal axes sampled linearly and as specified by a lookup table. The resulting standard is consistent with the existing FITS WCS standards and specifies a metadata set that achieves the aims enunciated above.
1409.1924
The re-distribution of matter in the cores of galaxy clusters
Laporte, White
Present cosmological N-body re-sims of the assembly of BCGs in rich clusters. At z=2 populate DM sub haloes with self-gravitating stellar systems whose abundance and structure match observed high-z galaxies. By z=0, mergers have built much larger galaxies at cluster center. Their DM density profiles are shallower than in corresponding DM only simulations, but their total mass density profiles (stars + DM) are quite similar. Differences are found only at radii where the effects of central BHs may be significant. DM density slopes shallower than gamma=1.0 occur for r/r_200 < 0.015, close to the half-light radii of the BCGs. Experiments support earlier suggestions that NFW-like profiles are an attractor for the hierarchical growth of structure in collision less systems -- total mass density profiles asymptote to the solution found in DM-only sims over the radial range where mergers produce significant mixing between stars and DM. Simulated DM fractions are substantially higher in BCGs than in field ellipticals, reaching 80% within the HLR. Also estimate that SMBH mergers should create BCG cores as large as r_c~3 kpc. The good agreement of all these properties with recent observational studies of BCG structure suggests that dissipation processes have not played a dominant role in the assembly of the observed systems.
1409.7389
Modeling the redshift-space three-point correlation function in SDSS-III
Guo et al
Present z-space 3PCF for z~0.5 CMASS LRGs in BOSS DR11. The 3PCF measurements are interpreted within the HOD framework using high-res N-body sims, and the model successfully reproduces the 3PCF on scales larger than 1 Mpc/h. As with the case for the z-space 2PCF, find that the z-space 3PCF measurements also require the inclusion of galaxy velocity bias in the model. In particular, the central galaxy in a halo on average is in motion wrt the core of the halo. Discuss the potential of the small-scale 3PCF to tighten the constraints on the relation between galaxies and DM haloes and on the phase-space distribution of galaxies.
1409.7395
GIZMO: a new class of accurate, mesh-free hydrodynamic simulation methods
Hopkins
Present and study 2 new Langrangian numerical methods for solving the equations of hydrodynamics, in a systematic comparison with moving-mesh, SPH, and non-moving grid methods. The new methods are designed to capture many advantages of both SPH and grid-based AMR schemes. They are based on a kernel discretization of the volume coupled to a high-order matrix gradient estimator and a Riemann solver acting over the volume 'overlap.' Implement and test a parallel, second-order version of the method with coupled self-gravity & cosmological integration, in the code GIZMO: this maintains exact mass, energy and momentum conservation; exhibits superior angular momentum conservation compared to all other methods studied; does not require 'artificial diffusion' terms; and allows fluid elements to move with the flow so resolution is automatically adaptive. Consider a large suite of test problems, and find that on all problems the new methods appear competitive with moving-mesh schemes, with some advantages (particularly in angular momentum conservation), at the cost of enhanced noise. The new methods have many advantages vs SPH: proper convergence, good capturing of fluid-mixing instabilities, dramatically reduced 'particle noise' & numerical viscosity, more accurate sub-sonic flow evolution, & numerical diffusion, velocity-independence of errors, accurate coupling to N-body gravity solvers, good angular momentum conservation, and elimination of 'grid alignment' effects. Can, for example, follow hundreds of orbits of gaseous disks, while AMR and SPH methods break down in a few orbits. All of these differences are important for a wide range of astrophysical problems.
1409.7398
The ancient heritage of water ice in the solar system
Cleeves et al
Identifying the source of Earth's water is central to understanding the origins of life-fostering environments and to assessing the prevalence of such environments in space. Water throughout the solar system exhibits D to H enrichments, a fossil relic of low-temperature, ion-derived chemistry within either (i) the parent molecular cloud or (ii) the solar nebular protoplanetary disk. Utilizing a comprehensive treatment of disk ionization, find that ion-driven D pathways are inefficient, curtailing the disk's D-water formation and its viability as the sole source for the SS's water. This finding implies that if the SS's formation was typical, abundant interstellar ices are available to all nascent planetary systems.
1409.7583
Representations of Time Coordinates in FITS
Rots et al
Time on all scales and precisions known in astronomical datasets is to be described in an unambiguous, complete, and self-consistent manner. Employing the well-established WCS framework, and maintaining compatibility with the FITS conventions that are currently in use to specify time, the standard is extended to describe rigorously the time coordinate. World coordinate functions are defined for temporal axes sampled linearly and as specified by a lookup table. The resulting standard is consistent with the existing FITS WCS standards and specifies a metadata set that achieves the aims enunciated above.
Thursday, September 25, 2014
Day 752
Friday.
1409.7084
The Next Generation BLAST experiment
Galityki et al
BLASTPol was a suborbital experiment designed to map B fields in order to study their role in SF processes. BLASTPol made detailed polarization maps of a number of molecular clouds during its successful flights from Antarctica in 2010 and 2012. Present the next-generation BLASTPol instrument (BOAST-TNG) that will build off the success of the previous experiment and continue its role as a unique instrument and a test bed for new technologies. With a 16-fold increase in mapping speed, BLAST-TNG will make larger and deeper maps. Major improvements include a 2.5m carbon fiber mirror that is 40% wider that the BLASTPol mirror and ~3000 polarization sensitive detectors. BLAST-TNG will observe in 3 bands at 250, 350, and 500 um. The telescope will surge as a pathfinder project for microwave kinetic inductance detector (MKID) technology, as applied to feed horn coupled sub millimeter detector arrays. The liquid He cooled cryostat will have a 28-day hold time and will utilize a closed-cycle 3He refrigerator to cool the detector arrays to 270 mK. This will enable a detailed mapping of more targets with higher polarization resolution than any other sub millimeter experiment to date. BLAST-TNG will also be the first balloon-borne telescope to offer shared risk observing time to the community. This paper outlines the motivation for the project and the instrumental design.
1409.7119
CANDELS/GOODS-S, CDFS, ECDEF: Photometric redshifts for normal and for X-ray-detected galaxies
Hsu et al
Photo-z and PDF for all sources in ECDFS, finding 1207 counterparts to the 1259 X-ray sources. Data used for photo-z include intermediate-band photometry deblended using the TFIT method, which is used for the first time in this work. Photo-z for X-ray source counterparts are based on a new library of AGN/galaxy hybrid templates appropriate for the faint X-ray population in the CDFS. Photo-z accuracy for normal galaxies is 0.010 and for X-ray sources is 0.014, and outlier fractions are 4% and 5.4% respectively. The results within the CANDELS coverage area are even better as demonstrated both by spectroscopic comparison and by galaxy-pair statistics. Intermediate-band photometry, even if shallow, is valuable when combined with deep broad-band photometry. For best accuracy, templates must include emission lines.
1409.7245
How to determine an exomoon's sense of orbital motion
Heller, Albrecht
Present two methods to determine an exomoon's sense of orbital motion (SOM), one respect to the planet's circumstellar orbit and one with respect to the planetary rotation. Simulations show E-ELT will be able to make these measurements. The first method relies on the mutual planet-moon events during stellar transits. Eclipses with the moon passing behind (in front of) the planet will be late (early) with regard to the moon's mean orbital period due to the finite speed of light. This "transit timing dichotomy" (TTD) determines an exomoon's SOM with respect to the circumstellar motion. For the ten largest moons in the solar system, TTDs range between 2 and 12 s. the E-ELT will enable such measurements for Earth-sized moons around nearby stars. The second method measures distortions in the IR spectrum of the rotation giant planet when it is transited by its moon. This Rossiter-McLaughlin effect (RME) in the planetary spectrum reveals the angle between the planetary equator and the moon's curcumplanetary orbital plane, and therefore unveils the moon's SOM with respect to the planet's rotation. A reasonably large moon transiting a directly imaged planet like beta Pic b cases an RME amplitude of almost 100 m/s, about twice the stellar RME amplitude of the transiting exoplanet HD209458b. Both new methods can be used to probe the origin of exomoons, that is, whether they are regular or irregular in nature.
1409.7295
Galaxy and mass assembly (GAMA): the unimodal nature of the dwarf galaxy population
Mahajan et al
Obtain light profile of 432 galaxies, multi-band photometry in 18 broad bands to obtain M*, SFR, sSFR and M_dust. Show that visually distinct, SF dwarf galaxies (irregulars, blue spheroids and low surface brightness galaxies) form a unimodal population in a parameter space mapped by mu_e, mu_0, n, r_e, SFR, sSFR, M*, M_dust and (g-i). The SFR and sSFR distribution of passively evolving (dwarf) ellipticals on the other hand, statistically distinguish them from other galaxies with similar luminosity, while the giant galaxies clearly segregate into SF spirals and passive lenticulars. Therefore suggest that the morphology classification scheme(s) used in the literature for dwarf galaxies only reflect the observational differences based on luminosity and surface brightness among the apparent distinct classes, rather than any physical differences between them.
1409.7297
Intrinsic alignments of galaxies in the MassiveBlack-II simulation: analysis of two-point statistics
Tenneti, Singh, Mandelbaum, et al
Present detailed measurements of the galaxy intrinsic alignments and associated ellipticity-direction (ED) and projected shape (w_g+) correlation functions for galaxies in the cosmological hydro MB-II simulation. Carefully asses the effects on galaxy shapes, misalignments and 2-pt statistics of iterative weighted (by mass, luminosity, and color) definition of the (reduced and unreduced) inertia tensor. Find that iterative procedures must be adopted for a reliable measurement of reduced tensor but that luminosity versus mass weighting has only negligible effects. Blue galaxies exhibit stronger misalignments and suppressed w_g+ amplitude. Both ED and w_g+ correlations increase in amplitude with sub halo mass (in the rage of 1e10-6e14 Msun/h), with a weak redshift dependence (from z=1 to z=0.06) at fixed mass. At z~0.3, predict a w_g+ that is in reasonable agreement with SDSS LRG measurements and that decreases in amplitude by a factor of ~5-18 for galaxies in the LSST survey. Predict the ratio of w_g+ (using sub haloes as tracers of density) and w_delta+ (using DM density) to exhibit a scale dependent bias on scales where the 1-halo term dominates. Also compared the IA of centrals and satellites, with clear detection of satellite radial alignments within their host haloes. Finally, show that w_g+ and w_delta+ predictions from the simulation agree with that of NL alignment models at scales where the 2-halo term dominates in the correlations (and tabulate associated NLA fitting parameters).
1409.7084
The Next Generation BLAST experiment
Galityki et al
BLASTPol was a suborbital experiment designed to map B fields in order to study their role in SF processes. BLASTPol made detailed polarization maps of a number of molecular clouds during its successful flights from Antarctica in 2010 and 2012. Present the next-generation BLASTPol instrument (BOAST-TNG) that will build off the success of the previous experiment and continue its role as a unique instrument and a test bed for new technologies. With a 16-fold increase in mapping speed, BLAST-TNG will make larger and deeper maps. Major improvements include a 2.5m carbon fiber mirror that is 40% wider that the BLASTPol mirror and ~3000 polarization sensitive detectors. BLAST-TNG will observe in 3 bands at 250, 350, and 500 um. The telescope will surge as a pathfinder project for microwave kinetic inductance detector (MKID) technology, as applied to feed horn coupled sub millimeter detector arrays. The liquid He cooled cryostat will have a 28-day hold time and will utilize a closed-cycle 3He refrigerator to cool the detector arrays to 270 mK. This will enable a detailed mapping of more targets with higher polarization resolution than any other sub millimeter experiment to date. BLAST-TNG will also be the first balloon-borne telescope to offer shared risk observing time to the community. This paper outlines the motivation for the project and the instrumental design.
1409.7119
CANDELS/GOODS-S, CDFS, ECDEF: Photometric redshifts for normal and for X-ray-detected galaxies
Hsu et al
Photo-z and PDF for all sources in ECDFS, finding 1207 counterparts to the 1259 X-ray sources. Data used for photo-z include intermediate-band photometry deblended using the TFIT method, which is used for the first time in this work. Photo-z for X-ray source counterparts are based on a new library of AGN/galaxy hybrid templates appropriate for the faint X-ray population in the CDFS. Photo-z accuracy for normal galaxies is 0.010 and for X-ray sources is 0.014, and outlier fractions are 4% and 5.4% respectively. The results within the CANDELS coverage area are even better as demonstrated both by spectroscopic comparison and by galaxy-pair statistics. Intermediate-band photometry, even if shallow, is valuable when combined with deep broad-band photometry. For best accuracy, templates must include emission lines.
1409.7245
How to determine an exomoon's sense of orbital motion
Heller, Albrecht
Present two methods to determine an exomoon's sense of orbital motion (SOM), one respect to the planet's circumstellar orbit and one with respect to the planetary rotation. Simulations show E-ELT will be able to make these measurements. The first method relies on the mutual planet-moon events during stellar transits. Eclipses with the moon passing behind (in front of) the planet will be late (early) with regard to the moon's mean orbital period due to the finite speed of light. This "transit timing dichotomy" (TTD) determines an exomoon's SOM with respect to the circumstellar motion. For the ten largest moons in the solar system, TTDs range between 2 and 12 s. the E-ELT will enable such measurements for Earth-sized moons around nearby stars. The second method measures distortions in the IR spectrum of the rotation giant planet when it is transited by its moon. This Rossiter-McLaughlin effect (RME) in the planetary spectrum reveals the angle between the planetary equator and the moon's curcumplanetary orbital plane, and therefore unveils the moon's SOM with respect to the planet's rotation. A reasonably large moon transiting a directly imaged planet like beta Pic b cases an RME amplitude of almost 100 m/s, about twice the stellar RME amplitude of the transiting exoplanet HD209458b. Both new methods can be used to probe the origin of exomoons, that is, whether they are regular or irregular in nature.
1409.7295
Galaxy and mass assembly (GAMA): the unimodal nature of the dwarf galaxy population
Mahajan et al
Obtain light profile of 432 galaxies, multi-band photometry in 18 broad bands to obtain M*, SFR, sSFR and M_dust. Show that visually distinct, SF dwarf galaxies (irregulars, blue spheroids and low surface brightness galaxies) form a unimodal population in a parameter space mapped by mu_e, mu_0, n, r_e, SFR, sSFR, M*, M_dust and (g-i). The SFR and sSFR distribution of passively evolving (dwarf) ellipticals on the other hand, statistically distinguish them from other galaxies with similar luminosity, while the giant galaxies clearly segregate into SF spirals and passive lenticulars. Therefore suggest that the morphology classification scheme(s) used in the literature for dwarf galaxies only reflect the observational differences based on luminosity and surface brightness among the apparent distinct classes, rather than any physical differences between them.
1409.7297
Intrinsic alignments of galaxies in the MassiveBlack-II simulation: analysis of two-point statistics
Tenneti, Singh, Mandelbaum, et al
Present detailed measurements of the galaxy intrinsic alignments and associated ellipticity-direction (ED) and projected shape (w_g+) correlation functions for galaxies in the cosmological hydro MB-II simulation. Carefully asses the effects on galaxy shapes, misalignments and 2-pt statistics of iterative weighted (by mass, luminosity, and color) definition of the (reduced and unreduced) inertia tensor. Find that iterative procedures must be adopted for a reliable measurement of reduced tensor but that luminosity versus mass weighting has only negligible effects. Blue galaxies exhibit stronger misalignments and suppressed w_g+ amplitude. Both ED and w_g+ correlations increase in amplitude with sub halo mass (in the rage of 1e10-6e14 Msun/h), with a weak redshift dependence (from z=1 to z=0.06) at fixed mass. At z~0.3, predict a w_g+ that is in reasonable agreement with SDSS LRG measurements and that decreases in amplitude by a factor of ~5-18 for galaxies in the LSST survey. Predict the ratio of w_g+ (using sub haloes as tracers of density) and w_delta+ (using DM density) to exhibit a scale dependent bias on scales where the 1-halo term dominates. Also compared the IA of centrals and satellites, with clear detection of satellite radial alignments within their host haloes. Finally, show that w_g+ and w_delta+ predictions from the simulation agree with that of NL alignment models at scales where the 2-halo term dominates in the correlations (and tabulate associated NLA fitting parameters).
Day 751
Thursday.
1409.6727
Near-infrared structure of fast and slow rotating disk galaxies
Schechtman-Rook, Bershady
Despite the differences within, all fast-rotating galaxies in the sample (of edge-on galaxies) have inner truncations in at least one of their disks (super-thin, think, thick). These truncations lead to Freeman Type II profiles when projected face-on. Slow-rotating galaxies are less complex, lacking inner disk truncations and require fewer disk components to reproduce their light distributions. Super-think disk components in undisturbed disks contribute ~25% of the total Ks-band light, up to that of the thin-disk contribution. The presence of super-thin disks correlates with IR flux ratios; galaxies with super-thin disks have f(Ks)/f(60 um)<0.12 for integrated light, consistent with super-thin disks being regions of on-going SF. Attenuation-corrected vertical color gradients in (J-Ks) correlate with the observed disk structure and are consistent with population gradients with young-to-intermediate ages closer to the mid plane, indicating that disk heating (or cooling) is a ubiquitous phenomenon.
1409.6727
Near-infrared structure of fast and slow rotating disk galaxies
Schechtman-Rook, Bershady
Despite the differences within, all fast-rotating galaxies in the sample (of edge-on galaxies) have inner truncations in at least one of their disks (super-thin, think, thick). These truncations lead to Freeman Type II profiles when projected face-on. Slow-rotating galaxies are less complex, lacking inner disk truncations and require fewer disk components to reproduce their light distributions. Super-think disk components in undisturbed disks contribute ~25% of the total Ks-band light, up to that of the thin-disk contribution. The presence of super-thin disks correlates with IR flux ratios; galaxies with super-thin disks have f(Ks)/f(60 um)<0.12 for integrated light, consistent with super-thin disks being regions of on-going SF. Attenuation-corrected vertical color gradients in (J-Ks) correlate with the observed disk structure and are consistent with population gradients with young-to-intermediate ages closer to the mid plane, indicating that disk heating (or cooling) is a ubiquitous phenomenon.
Wednesday, September 24, 2014
Day 750
Wednesday.
1409.6302
Lessons from the Local Group (and beyond) on dark matter
Kroupa
Why DM does cannot exist. (i) The two types of dwarf galaxies, the primordial dwarfs with DM and the tidal dwarf galaxies without DM, out to present clear observational difference, but there is no evidence for two separate families of dwarfs, neither in terms of their location relative to the baryon TF relation nor in forms of their radius-mass relation. And the arrangements in rotation disk-of-satellites, in particular around the MW and Andromeda, has been found to be only consistent with most of not all dwarf satellite galaxies being tidal dwarf galaxies. The highly symmetric structure of the entire LG too is inconsistent with its galaxies stemming from a stochastic merger-driven hierarchical buildup over cosmic time. (ii) Dynamical friction on the expansive and massive DM haloes is not evident in the data.
1409.6302
Lessons from the Local Group (and beyond) on dark matter
Kroupa
Why DM does cannot exist. (i) The two types of dwarf galaxies, the primordial dwarfs with DM and the tidal dwarf galaxies without DM, out to present clear observational difference, but there is no evidence for two separate families of dwarfs, neither in terms of their location relative to the baryon TF relation nor in forms of their radius-mass relation. And the arrangements in rotation disk-of-satellites, in particular around the MW and Andromeda, has been found to be only consistent with most of not all dwarf satellite galaxies being tidal dwarf galaxies. The highly symmetric structure of the entire LG too is inconsistent with its galaxies stemming from a stochastic merger-driven hierarchical buildup over cosmic time. (ii) Dynamical friction on the expansive and massive DM haloes is not evident in the data.
Monday, September 22, 2014
Day 749
Tuesday.
1409.5792
Impact of star formation history on the measurement of star formation rates
Boquien, Buat, Perret
Calculate SED from hydrosims of 1<z<2 galaxies every 1 Myr. Except for the Lyman continuum, classical SFR estimators calibrated over 100 Myr overestimate the SFR from ~25% in the FUV band to ~65% in the U band. Such biases are due 1) to the contribution of stars living longer than 100 Myr, and 2) to variations of the SFR on timescales longer than a few tens of Myr. Rapid variations of the SFR increase the uncertainty on the determination of the instantaneous SFR but have no long term effect. The discrepancies between the true and estimated SFR may explain at least part of the tension between the integral of the SFR density and the stellar mass density at a given redshift. To reduce possible biases, suggest to use SFR estimators calibrated over 1 Gyr rather than the usually adopted 100 Myr timescales.
1409.5905
SARCS strong-lensing galaxy groups: II - mass-concentration relation and strong-lensing bias
Foëx, Motta, Jullo, Limousin, Verdugo
Based on stacked WL analysis of 80 SL galaxy groups, find (i) the lensing signal does not allow a firm rejection of a simple SIS mass distribution compared to the expected NFW, (ii) obtain an average concentration c200=8.6pm2 that is much higher than the expected value from sims for the corresponding average mass M200=0.73e14 Msun, (iii) the combination of results with those at higher mass scales give a c(M) relation over nearly 2 decades in mass, with a slope in disagreement with predictions from numerical sims using unbiased populations of DM haloes, (iv) combined c(M) relation matches results from sims using only haloes with a large SL cross section, i.e., elongated with a major axis close to the LoS, (v) for the simplest case of prolate haloes, estimate with a toy model a lower limit on the minor:major axis ratio a/c=0.5 for the average SARCS galaxy group. Analysis based on galaxy groups confirmed the results obtained at larger mass scales: SL present apparently too large concentrations, which can be explained by traixial haloes preferentially orientated with the LoS. Because more massive systems already have large lensing cross section, they do not require a large elongation along the LoS, contrary to less massive galaxy groups. Therefore, it is natural to observed large lensing (projected) concentrations for such systems, resulting in an overall mass-concentration relation steeper than that of non-lensing haloes.
1409.6273
Impact of atmospheric chromatic effects on weak lensing measurements
Meyers, Burchat
Use analytic and computational techniques to study the impact on shape measurements of two atmospheric chromatic effects for ground-based surveys such as the DES and LSST: (i) atmospheric differential chromatic refraction (DCR) and (ii) wavelength dependence of seeing. Investigate the effects of using the PSF measured with stars to determine the sale of a galaxy that has a different SED than the stars. For (i), extend a study by Plazas & Bernstein based on analytic calculations that show that DCR leads to significant biases in galaxy shape measurements for future surveys, if not corrected. For (ii), find that the wavelength dependence of seeing leads to significant biases for galaxy shape measurements - even for current ground-based surveys. For both effects, investigate correction techniques based on multi-filter photometry. Using simulated galaxy images, find a form of chromatic "model bias" that arises when fitting a galaxy image with a model that has been convolved with a stellar, instead of galactic, PSF. Find that PSF-level corrections can reduce biases to levels that meet the requirements for the LSST survey. Conclude that achieving the ultimate precision for WL from current and future ground-based imaging surveys requires a detailed understanding of the wavelength dependence of the PSF in the atmosphere, and from other sources such as optics and sensors. The source code for analysis available on github.
1409.5792
Impact of star formation history on the measurement of star formation rates
Boquien, Buat, Perret
Calculate SED from hydrosims of 1<z<2 galaxies every 1 Myr. Except for the Lyman continuum, classical SFR estimators calibrated over 100 Myr overestimate the SFR from ~25% in the FUV band to ~65% in the U band. Such biases are due 1) to the contribution of stars living longer than 100 Myr, and 2) to variations of the SFR on timescales longer than a few tens of Myr. Rapid variations of the SFR increase the uncertainty on the determination of the instantaneous SFR but have no long term effect. The discrepancies between the true and estimated SFR may explain at least part of the tension between the integral of the SFR density and the stellar mass density at a given redshift. To reduce possible biases, suggest to use SFR estimators calibrated over 1 Gyr rather than the usually adopted 100 Myr timescales.
1409.5905
SARCS strong-lensing galaxy groups: II - mass-concentration relation and strong-lensing bias
Foëx, Motta, Jullo, Limousin, Verdugo
Based on stacked WL analysis of 80 SL galaxy groups, find (i) the lensing signal does not allow a firm rejection of a simple SIS mass distribution compared to the expected NFW, (ii) obtain an average concentration c200=8.6pm2 that is much higher than the expected value from sims for the corresponding average mass M200=0.73e14 Msun, (iii) the combination of results with those at higher mass scales give a c(M) relation over nearly 2 decades in mass, with a slope in disagreement with predictions from numerical sims using unbiased populations of DM haloes, (iv) combined c(M) relation matches results from sims using only haloes with a large SL cross section, i.e., elongated with a major axis close to the LoS, (v) for the simplest case of prolate haloes, estimate with a toy model a lower limit on the minor:major axis ratio a/c=0.5 for the average SARCS galaxy group. Analysis based on galaxy groups confirmed the results obtained at larger mass scales: SL present apparently too large concentrations, which can be explained by traixial haloes preferentially orientated with the LoS. Because more massive systems already have large lensing cross section, they do not require a large elongation along the LoS, contrary to less massive galaxy groups. Therefore, it is natural to observed large lensing (projected) concentrations for such systems, resulting in an overall mass-concentration relation steeper than that of non-lensing haloes.
1409.6273
Impact of atmospheric chromatic effects on weak lensing measurements
Meyers, Burchat
Use analytic and computational techniques to study the impact on shape measurements of two atmospheric chromatic effects for ground-based surveys such as the DES and LSST: (i) atmospheric differential chromatic refraction (DCR) and (ii) wavelength dependence of seeing. Investigate the effects of using the PSF measured with stars to determine the sale of a galaxy that has a different SED than the stars. For (i), extend a study by Plazas & Bernstein based on analytic calculations that show that DCR leads to significant biases in galaxy shape measurements for future surveys, if not corrected. For (ii), find that the wavelength dependence of seeing leads to significant biases for galaxy shape measurements - even for current ground-based surveys. For both effects, investigate correction techniques based on multi-filter photometry. Using simulated galaxy images, find a form of chromatic "model bias" that arises when fitting a galaxy image with a model that has been convolved with a stellar, instead of galactic, PSF. Find that PSF-level corrections can reduce biases to levels that meet the requirements for the LSST survey. Conclude that achieving the ultimate precision for WL from current and future ground-based imaging surveys requires a detailed understanding of the wavelength dependence of the PSF in the atmosphere, and from other sources such as optics and sensors. The source code for analysis available on github.
Sunday, September 21, 2014
Day 748
Monday.
1409.5432
Formation of dark matter torii around supermassive black holes via the eccentric Kozai-Lidov Mechanism
Naoz, Silk
Suggest that if the BHs are spinning, the accreted DM particles may linger in the ergosphere and thereby may generate self-annihilations and produce an indirect signature of potential interest.
1409.5433
The Herschel view of the dominant mode of galaxy growth from z=4 to the present day
Schreiber et al
Present an analysis of the deepest Hershcel images in GOODS-N/S, UDS and COSMOS. The picture provided by 10k individual FIR detentions is supplemented by the stacking analysis of a mass-complete sample of 62k SF galaxies from the CANDELS-HST H band-selected catalogs and from 2 deep ground-based Ks band-selected catalogs in the GOODS-N and COSMOS-w fields, in order to obtain one of the most accurate and unbiased understanding to date of the stellar mass growth over the cosmic history. Show, for the first time, that stacking also provides a powerful tool to determine the dispersion of a physical correlation and describe the method called "scatter stacking" that may be easily generalized to other experiments. Demonstrate that galaxies of all masses from z=4 to 0 follow a universal scaling law, the so-called MS of SF galaxies. Find a universal close-to-linear slope of the logSFR-logM* relation with a non varying dispersion of 0.3 dex. Also find evidence for a flattening of the MS at high masses (log(M*/Msun)>10.5) that becomes less prominent with increasing z and almost vanishes by z~2. It is tempting to associate this ending with the parallel growth of quiescent bulges in SF galaxies. The sSFR=SFR/M* of SF galaxies is found to continuously increase from z=0 to 4. Finally, discuss the implications of the findings on the cosmic SFR history and show that more than 2/3 of present-day stars must have formed in a regime dominated by the MS mode. As a consequence, conclude that although omnipresent in the distant Universe, galaxy mergers had little impact in triggering strong starbursts over the last 12.5 Gyr.
1409.5435
CoMaLit III. Literature catalogs of weak lensing clusters of galaxies (LC^2)
Sereno
Compiled, from the literature, a catalog of weak lensing clusters. Cluster ID, coordinates, and z have been standardized. WL masses were reported to over-densities of 2500, 500, 200, and to the virial one in the reference LCDM model. Duplicate entries were carefully handled. Produced 3 catalogs: LC^2-single, with 485 unique groups and cluster analyses with the single-halo model; LC^2-substructure, listing substructures in complex systems; LC^2-all, listing all the 822 WL masses found in literature. The catalogs are publicly available.
1409.5601
Mass - concentration relation and weak lensing peak counts
Cardone et al
The statistics of peaks in WL convergence maps is a promising tool to investigate both the properties of DM haloes and constrain the cosmo parameters. Study how the number of detectable peaks and its scaling with z depend upon the cluster DM halo profiles and use peak statistics to constrain the parameter of the m-c relation (MC). Investigate which constraints the Euclid mission can set on the MC coefficient also taking into account degeneracies with the cosmological parameters. To this end, first estimate the number of peaks and its z distribution for different MC relations. Find that the steeper the mass dependence and the larger the normalization, the higher is the number of detectable clusters, with the total number of peaks changing up to 40% depending on the MC relation. Then perform a Fisher matrix forecast of the errors on the MC relate parameters as well as cosmological parameters. Find that peak number counts detected by Euclid can determine the normalization Anu, the mass Bnu and redshift Cnu slopes and intrinsic scatter sigmanu of the MC relation to an unprecedented accuracy of 1% (relative) if all cosmo parameters are assumed to be known. Should this assumption be relaxed, constraints are degraded, but remarkably good results can be restored setting only some of the parameters of combining peak counts with Planck data. This precision can give insight on competing scenarios of structure formation and evolution and on the role of baryons in cluster assembling. Alternatively, for a fixed MC relation, future peaks counts can perform as well as current BAO and SNeIa when combined with Planck.
1409.5432
Formation of dark matter torii around supermassive black holes via the eccentric Kozai-Lidov Mechanism
Naoz, Silk
Suggest that if the BHs are spinning, the accreted DM particles may linger in the ergosphere and thereby may generate self-annihilations and produce an indirect signature of potential interest.
1409.5433
The Herschel view of the dominant mode of galaxy growth from z=4 to the present day
Schreiber et al
Present an analysis of the deepest Hershcel images in GOODS-N/S, UDS and COSMOS. The picture provided by 10k individual FIR detentions is supplemented by the stacking analysis of a mass-complete sample of 62k SF galaxies from the CANDELS-HST H band-selected catalogs and from 2 deep ground-based Ks band-selected catalogs in the GOODS-N and COSMOS-w fields, in order to obtain one of the most accurate and unbiased understanding to date of the stellar mass growth over the cosmic history. Show, for the first time, that stacking also provides a powerful tool to determine the dispersion of a physical correlation and describe the method called "scatter stacking" that may be easily generalized to other experiments. Demonstrate that galaxies of all masses from z=4 to 0 follow a universal scaling law, the so-called MS of SF galaxies. Find a universal close-to-linear slope of the logSFR-logM* relation with a non varying dispersion of 0.3 dex. Also find evidence for a flattening of the MS at high masses (log(M*/Msun)>10.5) that becomes less prominent with increasing z and almost vanishes by z~2. It is tempting to associate this ending with the parallel growth of quiescent bulges in SF galaxies. The sSFR=SFR/M* of SF galaxies is found to continuously increase from z=0 to 4. Finally, discuss the implications of the findings on the cosmic SFR history and show that more than 2/3 of present-day stars must have formed in a regime dominated by the MS mode. As a consequence, conclude that although omnipresent in the distant Universe, galaxy mergers had little impact in triggering strong starbursts over the last 12.5 Gyr.
1409.5435
CoMaLit III. Literature catalogs of weak lensing clusters of galaxies (LC^2)
Sereno
Compiled, from the literature, a catalog of weak lensing clusters. Cluster ID, coordinates, and z have been standardized. WL masses were reported to over-densities of 2500, 500, 200, and to the virial one in the reference LCDM model. Duplicate entries were carefully handled. Produced 3 catalogs: LC^2-single, with 485 unique groups and cluster analyses with the single-halo model; LC^2-substructure, listing substructures in complex systems; LC^2-all, listing all the 822 WL masses found in literature. The catalogs are publicly available.
1409.5601
Mass - concentration relation and weak lensing peak counts
Cardone et al
The statistics of peaks in WL convergence maps is a promising tool to investigate both the properties of DM haloes and constrain the cosmo parameters. Study how the number of detectable peaks and its scaling with z depend upon the cluster DM halo profiles and use peak statistics to constrain the parameter of the m-c relation (MC). Investigate which constraints the Euclid mission can set on the MC coefficient also taking into account degeneracies with the cosmological parameters. To this end, first estimate the number of peaks and its z distribution for different MC relations. Find that the steeper the mass dependence and the larger the normalization, the higher is the number of detectable clusters, with the total number of peaks changing up to 40% depending on the MC relation. Then perform a Fisher matrix forecast of the errors on the MC relate parameters as well as cosmological parameters. Find that peak number counts detected by Euclid can determine the normalization Anu, the mass Bnu and redshift Cnu slopes and intrinsic scatter sigmanu of the MC relation to an unprecedented accuracy of 1% (relative) if all cosmo parameters are assumed to be known. Should this assumption be relaxed, constraints are degraded, but remarkably good results can be restored setting only some of the parameters of combining peak counts with Planck data. This precision can give insight on competing scenarios of structure formation and evolution and on the role of baryons in cluster assembling. Alternatively, for a fixed MC relation, future peaks counts can perform as well as current BAO and SNeIa when combined with Planck.
Thursday, September 18, 2014
Day 747
Thursday. Friday.
1409.5130
The impact of sprious shear on cosmological parameter estimates from weak lensing observables
Petri, May, Haiman, Kratochvil
Residual errors in shear measurements, after corrections for instrument systematic and atmospheric effects, can impact cosmological parameter derived from WL observations. Combine convergence maps from ray-tracing sims with random realization of serious shear with a PS estimated from LSST. This allows to quantify the errors and biases on the triplet (Omega_m, w, sigma_8) derived from the PS, as well as from 3 different sets of non-Gaussian statistics of the lensing convergence field: Minkowski functionals (MF), low-order moments (LM), and peak counts (PK). Main results are: (i) find an order of magnitude smaller biases from the PS than in previous work. (ii) the PS and LM yield biases much smaller than the morphological statistics (MF, PK). (iii) For strictly Gaussian spurious shear with integrated amplitude as low as its current estimate of sigma^2_sys~1e-7, biases from the PS and LM would be unimportant even for a survey with the statistical power of LSST. However, find that for surveys larger than ~100 deg^2, non-Gaussianity in the noise (not included in the analysis) will likely be important and must be quantified to assess the biases. (iv) The morphological statistics (MF, PK) introduce important biases even for Gaussian noise, which must be corrected in large surveys. The biases are in different directions in (Omega_m, w, sigma_8) parameter space, allowing self-calibration by combining multiple statistics. Results warrant follow-up studies with more extensive lensing simulations and more accurate spurious shear estimates.
1409.5197
A theoretical estimate of intrinsic ellipticity bispectra induced by angular momenta alignments
Merkel, Schaefer
Results from sims suggest that 3rd order measures might be even stronger affected by IA. Investigate the (angular) bispectrum of IA. Describe IA by a physical alignment model, which makes use of tidal torque theory. Derive expressions for the various combinations of intrinsic and gravitationally induced ellipticities, i.e., III- GII- and GGI-alignments, and com are results to the shear bispectrum, the GGG-term. The latter is computed using hyper-extended perturbation theory. Considering equilateral and squeezed configurations, find that for a Euclid-like survey IA (III-alignemtns) start to dominate on angular scales smaller than 20 arcmin and 13 arcmin, respectively. This sensitivity to the configuration-space geometry may allow to exploit the cosmological information contained in both the intrinsic and gravitationally induced ellipticity field. On smallest scales (l~3000) III-alignments exceed the lensing signal by at least one order of magnitude. The amplitude of the GGI-alignments is the weakest. It stays below that of the shear field on all angular scales irrespective of the wave-vector configuration.
1409.5228
The physical origin of the universal accretion history of dark matter haloes
Correa, Wyithe, Schaye, Duffy
Assume extended Press-Schechter formalism; then explore the relation between the structure of the inner DM halos and halo mass history using a suite of cosmological, hydrodynamical simulations. Confirm that the formation time, defined as the time when the virial mass of the main progenitor equals the mass enclosed within the scale radius, correlates strongly with concentration. Provide a fitting formula for the relation between concentration and formation time, from which we show analytically that the scatter in formation time determines the scatter in concentration. Based on the analytic and numerical work, conclude that the concentration is determined by the halo mass history, and show by simple modeling that one can be determined from the other. Since halo concentrations are characterized by their mass histories, and the latter are described by the initial density perturbations and the growth rate, establish the physical link between halo concentrations and the initial density perturbation field. Finally, model the halo mass history as M(z)=M0(1+z)^{alpha}e^{beta z} and find a direct correlation between the parameters alpha, beta and concentration. Provide fitting formulas for the halo mass history and accretion rate as a function of halo mass, and demonstrate how halo mass history changes according to the adopted mass definition and cosmology.
1409.5130
The impact of sprious shear on cosmological parameter estimates from weak lensing observables
Petri, May, Haiman, Kratochvil
Residual errors in shear measurements, after corrections for instrument systematic and atmospheric effects, can impact cosmological parameter derived from WL observations. Combine convergence maps from ray-tracing sims with random realization of serious shear with a PS estimated from LSST. This allows to quantify the errors and biases on the triplet (Omega_m, w, sigma_8) derived from the PS, as well as from 3 different sets of non-Gaussian statistics of the lensing convergence field: Minkowski functionals (MF), low-order moments (LM), and peak counts (PK). Main results are: (i) find an order of magnitude smaller biases from the PS than in previous work. (ii) the PS and LM yield biases much smaller than the morphological statistics (MF, PK). (iii) For strictly Gaussian spurious shear with integrated amplitude as low as its current estimate of sigma^2_sys~1e-7, biases from the PS and LM would be unimportant even for a survey with the statistical power of LSST. However, find that for surveys larger than ~100 deg^2, non-Gaussianity in the noise (not included in the analysis) will likely be important and must be quantified to assess the biases. (iv) The morphological statistics (MF, PK) introduce important biases even for Gaussian noise, which must be corrected in large surveys. The biases are in different directions in (Omega_m, w, sigma_8) parameter space, allowing self-calibration by combining multiple statistics. Results warrant follow-up studies with more extensive lensing simulations and more accurate spurious shear estimates.
1409.5197
A theoretical estimate of intrinsic ellipticity bispectra induced by angular momenta alignments
Merkel, Schaefer
Results from sims suggest that 3rd order measures might be even stronger affected by IA. Investigate the (angular) bispectrum of IA. Describe IA by a physical alignment model, which makes use of tidal torque theory. Derive expressions for the various combinations of intrinsic and gravitationally induced ellipticities, i.e., III- GII- and GGI-alignments, and com are results to the shear bispectrum, the GGG-term. The latter is computed using hyper-extended perturbation theory. Considering equilateral and squeezed configurations, find that for a Euclid-like survey IA (III-alignemtns) start to dominate on angular scales smaller than 20 arcmin and 13 arcmin, respectively. This sensitivity to the configuration-space geometry may allow to exploit the cosmological information contained in both the intrinsic and gravitationally induced ellipticity field. On smallest scales (l~3000) III-alignments exceed the lensing signal by at least one order of magnitude. The amplitude of the GGI-alignments is the weakest. It stays below that of the shear field on all angular scales irrespective of the wave-vector configuration.
1409.5228
The physical origin of the universal accretion history of dark matter haloes
Correa, Wyithe, Schaye, Duffy
Assume extended Press-Schechter formalism; then explore the relation between the structure of the inner DM halos and halo mass history using a suite of cosmological, hydrodynamical simulations. Confirm that the formation time, defined as the time when the virial mass of the main progenitor equals the mass enclosed within the scale radius, correlates strongly with concentration. Provide a fitting formula for the relation between concentration and formation time, from which we show analytically that the scatter in formation time determines the scatter in concentration. Based on the analytic and numerical work, conclude that the concentration is determined by the halo mass history, and show by simple modeling that one can be determined from the other. Since halo concentrations are characterized by their mass histories, and the latter are described by the initial density perturbations and the growth rate, establish the physical link between halo concentrations and the initial density perturbation field. Finally, model the halo mass history as M(z)=M0(1+z)^{alpha}e^{beta z} and find a direct correlation between the parameters alpha, beta and concentration. Provide fitting formulas for the halo mass history and accretion rate as a function of halo mass, and demonstrate how halo mass history changes according to the adopted mass definition and cosmology.
Wednesday, September 17, 2014
Day 746
Wednesday.
1409.4413
First CO(17-16) emission line detected in a z>6 quasar
Gallerani et al
CO(17-16) line possibly contaminated by OH+ emission that may account for 35-60% of the total flux observed. Photo-dissociation and X-ray Dominated regions (PDRs and XDRs) models show that PDRs alone cannot reproduce the high luminosity of the CO line relative to the low-J CO transitions and that XDRs are required. By adopting a composite PDR+XDR model, derive molecular cloud and radiation field properties in the nuclear region of J1148. Results show that highly excited CO lines represent a sensitive and possibly unique tool to infer the presence of X-ray faint or obscured SMBH progenitors in high-z galaxies.
1409.4414
Magnetic flux of progenitor stars sets gamma-ray burst luminosity and variability
Tchekhovskoy, Giannios
LGRBs are though to come from core-collapse of WR stars; their stellar masses M* have a rather narrow distribution, but the population of GRBs is very diverse (gamma ray luminosities span several orders of magnitude). Argue that the difference is the star's large-scale magnetic flux. Shortly after the core collapse, most of stellar B flux accumulates near the BH and remains there. The flux extracts BH rotational energy and powers jets of roughly a constant luminosity, Lj, However, once BH mass accretion rate Mdot falls below ~Lj/c2, the flux becomes dynamically important and diffuses outwards, with the jet luminosity set by the rapidly declining mass accretion rate, Lj~Mdot c2. This provides a potential explanation for the sharp end of GRBs and the universal shape of their light curves. During the GRB, gas infall translates spatial variation of stellar B flux into temporal variation of Lj. Make use of the deviations from constancy in Lj to perform stellar B flux "tomography". Using this method, infer the presence of magnetized tori in the outer layers of progenitor stars for GRB 920513 and GRB 940210.
1409.4422
Imprints of the quasar structure in time-delay light curves: microlensing-aided reverberation mapping
Sluse, Tewes
Owing to the advent of large photometric surveys, the possibility to use broad band photometric data instead of spectra to measure the size of the broad line region of AGN has raised a large interest. Describe a new method using time-delay lensed quasars where one of several images are affected by microlensing due to stars in the lensing galaxy. Because microlensing decreases (or increases) the flux of the continuum compared to the broad line region, it changes the contrast between these two emission components. Show that this effect can be used to effectively disentangle the intrinsic variability of those two regions, offering the opportunity to perform reverberation mapping based on single band photometric data. Based on simulated light curves generated using a damped random walk model of quasar variability, show that measurement of the size of the broad line region can be achieved using this method, provided one spectrum has been obtained independently during the monitoring. This method is complementary to photometric reverberation mapping and could also be extended to multi-band data. Because the effect described above produces a variability pattern in difference light curves between pairs of lensed images which is correlated with the time-lagged continuum variability, it can potentially produce systematic errors in measurement of time delays between pairs of lensed images. Simple simulations indicate that time-delay measurement techniques which use a sufficiently flexible model for the extrinsic variability are not affected by this effect and produce accurate time delays.
1409.4482
Splashback in accreting dark matter halos
Adhikari, Dala, Chamberlain
Recent work has shown that density profiles in the outskirts of DM haloes can become extremely steep over a narrow range of radius. This behavior is produced by splash back material on its first apocentric passage after accretion. Show that the location of this splash back feature may be understood quite simply, from first principles. Present a simple model, based on spherical collapse, that accurately predicts the location of splash back without any free parameters. The important quantities that determine the splash back radius are accretion rate and redshift.
1409.4650
Constraining dark sector perturbations I: cosmic shear and CMB lensing
Battye, Moss, Pearson
Present current and future constraints on EoS for dark sector perturbations. EoS considered are those corresponding to a generalized scalar field model and time-diffeomorphism invariant L(g) theories that are equivalent to models of a relativistic elastic medium and also Lorentz violating massive gravity. Develop a theoretical understanding of the observable impact of these models. In order to constrain these models, use CMB temperature data from Planck, BAO measurements, CMB lensing data from Planck and the SPT, and weak galaxy lensing data from CFHTLenS. Find non-trivial exclusions on the range of parameters, although the data remains compatible with w=-1. Gauge how future experiments will help to constrain the parameters. This is done via a likelihood analysis for CMB experiments such as CoRE and PRISM, and tomographic galaxy WL surveys, focusing on the potential discriminatory power of Euclid on mildly NL scales.
1409.4681
Galaxy and mass assembly (GAMA): the dependence of the galaxy luminosity function on environment, redshift and color
McNaught-Roberts, Norberg, Baugh, Lacey, Loveday, Peacock, ... et al
Use 80k galaxies in GAMA to measure galaxy LF in different environments in 0.04<z<0.26. The depth and size of GAMA allows samples split by color and z to measure the dependence of LF on environment, z and color. Find that the LF varies smoothly with overdensity, consistent with previous results, with little environmental dependent evolution over the last 3 Gyrs. The modified GALFORM model predictions agree remarkable well with the LFs split by environment, particularly in the most over dense environments. The LFs predicted by the model for both blue and red galaxies are consistent with GAMA for the environments and luminosities at which such galaxies dominate. Discrepancies between the model and the data seen in the faint end of the LF suggest too many faint red galaxies are predicted, which is likely due to the over-quenching of satellite galaxies. The excess of bright blue galaxies predicted in under dense regions could be due to the implementation of AGN feedback not being sufficiently effective in the lower mass haloes.
1409.4413
First CO(17-16) emission line detected in a z>6 quasar
Gallerani et al
CO(17-16) line possibly contaminated by OH+ emission that may account for 35-60% of the total flux observed. Photo-dissociation and X-ray Dominated regions (PDRs and XDRs) models show that PDRs alone cannot reproduce the high luminosity of the CO line relative to the low-J CO transitions and that XDRs are required. By adopting a composite PDR+XDR model, derive molecular cloud and radiation field properties in the nuclear region of J1148. Results show that highly excited CO lines represent a sensitive and possibly unique tool to infer the presence of X-ray faint or obscured SMBH progenitors in high-z galaxies.
1409.4414
Magnetic flux of progenitor stars sets gamma-ray burst luminosity and variability
Tchekhovskoy, Giannios
LGRBs are though to come from core-collapse of WR stars; their stellar masses M* have a rather narrow distribution, but the population of GRBs is very diverse (gamma ray luminosities span several orders of magnitude). Argue that the difference is the star's large-scale magnetic flux. Shortly after the core collapse, most of stellar B flux accumulates near the BH and remains there. The flux extracts BH rotational energy and powers jets of roughly a constant luminosity, Lj, However, once BH mass accretion rate Mdot falls below ~Lj/c2, the flux becomes dynamically important and diffuses outwards, with the jet luminosity set by the rapidly declining mass accretion rate, Lj~Mdot c2. This provides a potential explanation for the sharp end of GRBs and the universal shape of their light curves. During the GRB, gas infall translates spatial variation of stellar B flux into temporal variation of Lj. Make use of the deviations from constancy in Lj to perform stellar B flux "tomography". Using this method, infer the presence of magnetized tori in the outer layers of progenitor stars for GRB 920513 and GRB 940210.
1409.4422
Imprints of the quasar structure in time-delay light curves: microlensing-aided reverberation mapping
Sluse, Tewes
Owing to the advent of large photometric surveys, the possibility to use broad band photometric data instead of spectra to measure the size of the broad line region of AGN has raised a large interest. Describe a new method using time-delay lensed quasars where one of several images are affected by microlensing due to stars in the lensing galaxy. Because microlensing decreases (or increases) the flux of the continuum compared to the broad line region, it changes the contrast between these two emission components. Show that this effect can be used to effectively disentangle the intrinsic variability of those two regions, offering the opportunity to perform reverberation mapping based on single band photometric data. Based on simulated light curves generated using a damped random walk model of quasar variability, show that measurement of the size of the broad line region can be achieved using this method, provided one spectrum has been obtained independently during the monitoring. This method is complementary to photometric reverberation mapping and could also be extended to multi-band data. Because the effect described above produces a variability pattern in difference light curves between pairs of lensed images which is correlated with the time-lagged continuum variability, it can potentially produce systematic errors in measurement of time delays between pairs of lensed images. Simple simulations indicate that time-delay measurement techniques which use a sufficiently flexible model for the extrinsic variability are not affected by this effect and produce accurate time delays.
1409.4482
Splashback in accreting dark matter halos
Adhikari, Dala, Chamberlain
Recent work has shown that density profiles in the outskirts of DM haloes can become extremely steep over a narrow range of radius. This behavior is produced by splash back material on its first apocentric passage after accretion. Show that the location of this splash back feature may be understood quite simply, from first principles. Present a simple model, based on spherical collapse, that accurately predicts the location of splash back without any free parameters. The important quantities that determine the splash back radius are accretion rate and redshift.
1409.4650
Constraining dark sector perturbations I: cosmic shear and CMB lensing
Battye, Moss, Pearson
Present current and future constraints on EoS for dark sector perturbations. EoS considered are those corresponding to a generalized scalar field model and time-diffeomorphism invariant L(g) theories that are equivalent to models of a relativistic elastic medium and also Lorentz violating massive gravity. Develop a theoretical understanding of the observable impact of these models. In order to constrain these models, use CMB temperature data from Planck, BAO measurements, CMB lensing data from Planck and the SPT, and weak galaxy lensing data from CFHTLenS. Find non-trivial exclusions on the range of parameters, although the data remains compatible with w=-1. Gauge how future experiments will help to constrain the parameters. This is done via a likelihood analysis for CMB experiments such as CoRE and PRISM, and tomographic galaxy WL surveys, focusing on the potential discriminatory power of Euclid on mildly NL scales.
1409.4681
Galaxy and mass assembly (GAMA): the dependence of the galaxy luminosity function on environment, redshift and color
McNaught-Roberts, Norberg, Baugh, Lacey, Loveday, Peacock, ... et al
Use 80k galaxies in GAMA to measure galaxy LF in different environments in 0.04<z<0.26. The depth and size of GAMA allows samples split by color and z to measure the dependence of LF on environment, z and color. Find that the LF varies smoothly with overdensity, consistent with previous results, with little environmental dependent evolution over the last 3 Gyrs. The modified GALFORM model predictions agree remarkable well with the LFs split by environment, particularly in the most over dense environments. The LFs predicted by the model for both blue and red galaxies are consistent with GAMA for the environments and luminosities at which such galaxies dominate. Discrepancies between the model and the data seen in the faint end of the LF suggest too many faint red galaxies are predicted, which is likely due to the over-quenching of satellite galaxies. The excess of bright blue galaxies predicted in under dense regions could be due to the implementation of AGN feedback not being sufficiently effective in the lower mass haloes.
Monday, September 15, 2014
Day 745
Tuesday.
1409.3845
Scaling properties of a complete X-ray selected galaxy group sample
Lovisari, Reiprich, Schellenberger
Main goal of this work is to constrain the galaxy group scaling relations corrected for select effects, and to quantify the influence of non-graviataional physics and the low-mass regime. Analyze XMM-Newton observations for a complete sample of galaxy groups selected from ROSAT All-Sky Survey and compare the derived scaling properties with a galaxy cluster sample. To investigate the role played by the different non-gravitational processes, compare the observational data with the predictions of hydrodynamical simulations. After applying the correction for selection effects, the L-M relation is steeper than the observed one. Its slope is also steeper than the value obtained by using the more massive systems of the HIFLUGCS sample. This behavior can be explained by a gradual change of the true L-M relation which should be taken into account when converting the observational parameters into masses. The other observed scaling relations (not corrected for selection biases) do not show any break although the comparison with the simulations suggests that feedback processes play an important role in the formation and evolution of galaxy groups. Thanks to the master sample of 82 objects spanning two order of magnitude in mass, tightly constrain the dependence of the gas mass fraction on the total mass, finding almost a factor of two difference between groups and clusters.
1409.3992
The rich complexity of 21-cm fluctuations produced by the first stars
Fialkov, Barkana
Explore the complete history of the 21-cm signal in z=7-40, including various epochs of cosmic evolution related to primordial SF, and should be accessible to existing or planned low-frequency radio telescopes. Use semi-numerical computational methods to explore the fluctuation signal over wave numbers between 0.03 and 1 /Mpc, accounting for the homogeneous backgrounds of Ly-a, X-ray, Lyman-Werner and ionizing radiation. Focus on the recently noted expectation of heating dominated by a hard X-ray spectrum from high-mass X-ray binaries. Study the resulting delayed cosmic heating and suppression of gas temperature fluctuations, allowing for large variations in the minimum halo mass that contributes to star formation. Show that the wave numbers at which the heating peak is detected in observations should tell us about the characteristic mean free path and spectrum of the emitted photons, thus giving key clues as to the character of the sources that heated the primordial Universe. Also consider the LoS anisotropy, which allows additional information to be extracted from the 21-cm signal. For example, the heating transition at which the cosmic gas is heated to the temperature of the CMB should be clearly marked by an especially isotropic PS. More generally, an additional cross-power component Px directly probes which sources dominated 21-cm fluctuations. In particular, during cosmic deionization (and after the just-mentioned heating transition), Px is negative on scales dominated by ionization fluctuations and positive on those dominated by temperature fluctuations.
1409.3845
Scaling properties of a complete X-ray selected galaxy group sample
Lovisari, Reiprich, Schellenberger
Main goal of this work is to constrain the galaxy group scaling relations corrected for select effects, and to quantify the influence of non-graviataional physics and the low-mass regime. Analyze XMM-Newton observations for a complete sample of galaxy groups selected from ROSAT All-Sky Survey and compare the derived scaling properties with a galaxy cluster sample. To investigate the role played by the different non-gravitational processes, compare the observational data with the predictions of hydrodynamical simulations. After applying the correction for selection effects, the L-M relation is steeper than the observed one. Its slope is also steeper than the value obtained by using the more massive systems of the HIFLUGCS sample. This behavior can be explained by a gradual change of the true L-M relation which should be taken into account when converting the observational parameters into masses. The other observed scaling relations (not corrected for selection biases) do not show any break although the comparison with the simulations suggests that feedback processes play an important role in the formation and evolution of galaxy groups. Thanks to the master sample of 82 objects spanning two order of magnitude in mass, tightly constrain the dependence of the gas mass fraction on the total mass, finding almost a factor of two difference between groups and clusters.
1409.3992
The rich complexity of 21-cm fluctuations produced by the first stars
Fialkov, Barkana
Explore the complete history of the 21-cm signal in z=7-40, including various epochs of cosmic evolution related to primordial SF, and should be accessible to existing or planned low-frequency radio telescopes. Use semi-numerical computational methods to explore the fluctuation signal over wave numbers between 0.03 and 1 /Mpc, accounting for the homogeneous backgrounds of Ly-a, X-ray, Lyman-Werner and ionizing radiation. Focus on the recently noted expectation of heating dominated by a hard X-ray spectrum from high-mass X-ray binaries. Study the resulting delayed cosmic heating and suppression of gas temperature fluctuations, allowing for large variations in the minimum halo mass that contributes to star formation. Show that the wave numbers at which the heating peak is detected in observations should tell us about the characteristic mean free path and spectrum of the emitted photons, thus giving key clues as to the character of the sources that heated the primordial Universe. Also consider the LoS anisotropy, which allows additional information to be extracted from the 21-cm signal. For example, the heating transition at which the cosmic gas is heated to the temperature of the CMB should be clearly marked by an especially isotropic PS. More generally, an additional cross-power component Px directly probes which sources dominated 21-cm fluctuations. In particular, during cosmic deionization (and after the just-mentioned heating transition), Px is negative on scales dominated by ionization fluctuations and positive on those dominated by temperature fluctuations.
Day 744
Monday.
1409.3566
Tracing chemical evolution over the extent of the Milky Way's disk with APOGE red comp stars
Nidever, et al
Employ SDSS-III/APOGEE spectra survey to investigate the distribution of metallicity and alpha-element abundances of stars over a large part of the MW disk. Use a sample of ~10k kinematically-unbiased red-clump stars with ~5% distance accuracy as tracers, the [alpha/Fe] vs [Fe/H] distribution of this sample exhibits a bimodality in [alpha/Fe] at intermediate metallicities, -0.9<[Fe/H]<-0.2, but at higher metallicities ([Fe/H]=+0.2) the two sequences smoothly merge. Investigate the effects of the APOGEE selection function and volume filling fraction and find that these have lithe qualitative impact on the alpha-element abundance patterns. The described abundance pattern is found throughout the range 5<R<11kpc and 0<|Z|<2 kpc across the Galaxy. The [alpha/Fe] trend of the high-alpha sequence is surprisingly constant throughout the Galaxy, with little variation from region to region (~10%). Using simple galactic chemical evolution models, derive an average SFE in the high-alpha sequence of ~4.5e-10 / yr, which is quite close to the nearly-constant value found in molecular-gas-dominated regions of nearby spirals. This result suggests that the early evolution of the MW disk was characterized by stars that shared a similar SFH and were formed in a well-mixed, turbulent, and molecular-domiated ISM with a gas consumption timescale (1/SFE) of ~2 Gyr. Finally, while the two alpha-element sequences in the inner Galaxy can be explained by a single chemical evolutionary track, this cannot hold in the outer Galaxy, requiring instead a mix of two or more population with distinct enrichment histories.
1409.3571
CFHTLenS: a weak lensing shear analysis of the 3D-matched-filter galaxy clusters
Ford, Van Waerbeke, ... etal
Present the cluster mass-richness scaling relation calibrated by WL analysis of >18k galaxy cluster candidates in CFHTLenS. Detected using the 3D-Matched-Filter cluster-finder of Milkeraitis+, these cluster candidates span a wide range of masses, from the small group scale up to ~1e15 Msun, and 0.2<z<0.9. The total significance of the shear measurement abounds to 54 sigma. Compare cluster masses determined using WL shear and magnification, finding the measurements in individual richness binds to yield 1 sigma compatibility, but with magnification estimates biased low. This first direct mass comparison yields important insights for improving the systematics handling of future lensing magnification work. In addition, confirm analyses that suggest cluster miscentering has an important effect on the observed 3D-Matched-Filter halo profiles, and quantify this by fitting for projected cluster centered offsets, which are typically ~0.4 arcmin. Bin the cluster candidates as a function of redshift, finding similar cluster masses and richness across the full range up to z~0.9. Measure the 3D-MF mass-richness scaling relation M_200=M0(N_200/20)^beta. Find a normalization M0~2.7e13 Msun, and a log slope of beta~1.4pm0.1, both of which are in 1 sigma agreement with results from the magnification analysis. Find no evidence for a redshift-dependence of the normalization. The CFHTLenS 3D-Matched-Filter cluster catalogue is now available.
1409.3697
A novel null test for the $\Lambda$CDM model with growth-rate data
Nesseris, Sapone
Present an alternative consistency check at the perturbative level for a homogeneous and isotropic Universe filled with a DE component. This test makes use of the growth of matter perturbations data and it is able to not only test the homogeneous and isotropic Universe but also, within the framework of a Friedmann-Lemaitre-Robertson Walker Universe, if the DE component is able to cluster, if there is a tension in the data or if we are dealing with a modification of gravity.
1409.3708
Testing gravity theories using stars
Sakstein, Jain, Vikram
Modified gravity satisfies cosmic acceleration; to satisfy solar system test of gravity, a theory needs to include a screening mechanism that hides the modifications on small scales. One popular and well-studied theory is chameleon gravity. Our own galaxy is necessarily screened, but less dense dwarf galaxies may be unscreened and their constituent stars can exhibit novel features. In particular, unscreened stars are brighter, hotter and more ephemeral than screens stars in our own galaxy. They also pulsate with a shorter period. In this essay, exploit these new features to constrain chameleon gravity to levels 3 orders of magnitude lower the previous measurements. These constraints are currently the strongest in the literature.
1409.3566
Tracing chemical evolution over the extent of the Milky Way's disk with APOGE red comp stars
Nidever, et al
Employ SDSS-III/APOGEE spectra survey to investigate the distribution of metallicity and alpha-element abundances of stars over a large part of the MW disk. Use a sample of ~10k kinematically-unbiased red-clump stars with ~5% distance accuracy as tracers, the [alpha/Fe] vs [Fe/H] distribution of this sample exhibits a bimodality in [alpha/Fe] at intermediate metallicities, -0.9<[Fe/H]<-0.2, but at higher metallicities ([Fe/H]=+0.2) the two sequences smoothly merge. Investigate the effects of the APOGEE selection function and volume filling fraction and find that these have lithe qualitative impact on the alpha-element abundance patterns. The described abundance pattern is found throughout the range 5<R<11kpc and 0<|Z|<2 kpc across the Galaxy. The [alpha/Fe] trend of the high-alpha sequence is surprisingly constant throughout the Galaxy, with little variation from region to region (~10%). Using simple galactic chemical evolution models, derive an average SFE in the high-alpha sequence of ~4.5e-10 / yr, which is quite close to the nearly-constant value found in molecular-gas-dominated regions of nearby spirals. This result suggests that the early evolution of the MW disk was characterized by stars that shared a similar SFH and were formed in a well-mixed, turbulent, and molecular-domiated ISM with a gas consumption timescale (1/SFE) of ~2 Gyr. Finally, while the two alpha-element sequences in the inner Galaxy can be explained by a single chemical evolutionary track, this cannot hold in the outer Galaxy, requiring instead a mix of two or more population with distinct enrichment histories.
1409.3571
CFHTLenS: a weak lensing shear analysis of the 3D-matched-filter galaxy clusters
Ford, Van Waerbeke, ... etal
Present the cluster mass-richness scaling relation calibrated by WL analysis of >18k galaxy cluster candidates in CFHTLenS. Detected using the 3D-Matched-Filter cluster-finder of Milkeraitis+, these cluster candidates span a wide range of masses, from the small group scale up to ~1e15 Msun, and 0.2<z<0.9. The total significance of the shear measurement abounds to 54 sigma. Compare cluster masses determined using WL shear and magnification, finding the measurements in individual richness binds to yield 1 sigma compatibility, but with magnification estimates biased low. This first direct mass comparison yields important insights for improving the systematics handling of future lensing magnification work. In addition, confirm analyses that suggest cluster miscentering has an important effect on the observed 3D-Matched-Filter halo profiles, and quantify this by fitting for projected cluster centered offsets, which are typically ~0.4 arcmin. Bin the cluster candidates as a function of redshift, finding similar cluster masses and richness across the full range up to z~0.9. Measure the 3D-MF mass-richness scaling relation M_200=M0(N_200/20)^beta. Find a normalization M0~2.7e13 Msun, and a log slope of beta~1.4pm0.1, both of which are in 1 sigma agreement with results from the magnification analysis. Find no evidence for a redshift-dependence of the normalization. The CFHTLenS 3D-Matched-Filter cluster catalogue is now available.
1409.3697
A novel null test for the $\Lambda$CDM model with growth-rate data
Nesseris, Sapone
Present an alternative consistency check at the perturbative level for a homogeneous and isotropic Universe filled with a DE component. This test makes use of the growth of matter perturbations data and it is able to not only test the homogeneous and isotropic Universe but also, within the framework of a Friedmann-Lemaitre-Robertson Walker Universe, if the DE component is able to cluster, if there is a tension in the data or if we are dealing with a modification of gravity.
1409.3708
Testing gravity theories using stars
Sakstein, Jain, Vikram
Modified gravity satisfies cosmic acceleration; to satisfy solar system test of gravity, a theory needs to include a screening mechanism that hides the modifications on small scales. One popular and well-studied theory is chameleon gravity. Our own galaxy is necessarily screened, but less dense dwarf galaxies may be unscreened and their constituent stars can exhibit novel features. In particular, unscreened stars are brighter, hotter and more ephemeral than screens stars in our own galaxy. They also pulsate with a shorter period. In this essay, exploit these new features to constrain chameleon gravity to levels 3 orders of magnitude lower the previous measurements. These constraints are currently the strongest in the literature.
Friday, September 12, 2014
Day 743
Friday.
1409.3238
The clustering of the SDSS main galaxy sample II: mock galaxy catalogue and a measurement of the growth of structure from redshift space distortions at $z=0.15$
Howlett, Ross, Samushia, Percival, Manera
Measure RSD in 2pt correlation function of 63k spec-z galaxies with z<0.2, an epoch where there are currently only limited measurements from SDSS7 Main sample. This sample, denoted MGS, covers 6k sq deg with z_eff=0.15 which concentrates on BAO measurements. In order to validate the fitting methods and derive errors, create and analyze 1000 mock catalogues using a new algorithm called PICOLA to generate accurate DM fields. Haloes are then selected using a FoF algorithm, and populated with galaxies using HOD fitted to the data. Fit a model to the monopole and quadrupole moments of the MGS correlation function, including both the RSD and AP effect, the latter of which results in anisotropic distortions if the wrong distance-redshift relation is used. This gives a measurement of f(z_eff) sigma8(z_eff)=0.53pm0.19. Assuming a fixed fiducial cosmology for the distance-z relationship based on recent Planck results, constraints on the growth rate tighten to f(z_eff) sigma8(z_eff)=0.44pm0.1. Combine measurement with recent CMB and BAO data allows constraint on the growth index of fluctuations, gamma. Assuming a BG LCDM cosmology, find gamma = 0.64pm0.09, which is consistent with the prediction of GR (gamma~0.55), though with a slight preference for higher gamma and hence models with weaker gravitational interactions.
1409.3242
The clustering of the SDSS DR7 Main Galaxy sample I: a 4 per cent distance measure at z=0.15
Ross, Samushia, Howlett, Percival, Burden, Manera
Create a sample of z<0.2 spec-z galaxies from SDSS DR7, covering 6813 sq deg. Galaxies are chosen to sample the highest mass haloes, with an effective bias of 1.5, allowing construction of 1000 mock galaxy catalogs, which is used to estimate statistical errors and test methods. Use an estimate of the gravitational potential to "reconstruct" the linear density fluctuations, enhancing BAO signal in the measured correlation function band PS. Fitting to these measurements, determine D(z_eff=0.15)=644pm25(rd/rd_fid) Mpc, this s a better than 4% distance measurement. This "fills the gap" in BAO distance ladder between previously measured local and higher z measurements, and affords significant improvement in constraining the properties of DE. Combining measurement with other BAO measurements from BOSS and 6dFGS galaxy samples provides a 15% improvement n the determination of the EoS of DE and the value of the Hubble parameter at z=0 (H0). Our measurement is fully consistent with the Planck results and the LCDM concordance cosmology, but increases the tension between Planck+BAO H0 determinations and direct H0 measurements.
1409.3364
Cosmological parameter constraints from CMB lensing with cosmic voids
Chantavat, Sawangwit, Sutter, Wandelt
Detecting a series of ~10 voids of size RV>20 Mpc/h along a LoS with 100-200 independent sq deg patches of the sky can potentially constrain cosmo parameters that are competitive with PLANCK alone. The chance of finding such patches are seemingly small. This analysis is based on current knowledge of the average void profiles and analytical estimates of the void number function in upcoming surveys. The full potential of this technique relies on an accurate determination of the void profile to ~10% level. CMB lensing with voids will provide a competitive and complimentary rout to parameter constraints for the next generation cosmo observations.
1409.3409
CosmoSIS: modula cosmological parameter estimation
Zuntz et al
Present a new framework for cosmo parameter estimation, CosmoSIS, designed to connect together, share, and advance development of inference tools across the community. Describe the modules already available in CosmoSIS, including CAMB, Planck, cosmic shear calculations, and a suite of samplers.
1409.3528
Gender-based systematics in HST proposal selection
Reid
Proposal success rates calculated for HST cycles 11 through 21 as a function of gender of the PI. In each cycle, proposals with male PIs have a higher success rate, with the disparity greatest for Cycles 12 and 18. The offsets are small enough that they might be ascribed to chance for any single cycle, but the consistent pattern suggests the presence of a systematic effect. Closer inspection of results from Cycles 19, 20 and 21 shows that the systematic difference does not appear to depend on the geographic origin of the proposal nor does it depend on the gender distribution on the review panels. Segregating proposals by the seniority of the PI, the success rates by gender for more recent graduates (Phd since 2000) are more closely comparable. There is also a correlation between success by gender and the average seniority of the review panel for Cycles 19, 20 but not 21. Discuss these results and some consequent changes to the proposal format and additions to the HST TAC orientation process.
1409.3238
The clustering of the SDSS main galaxy sample II: mock galaxy catalogue and a measurement of the growth of structure from redshift space distortions at $z=0.15$
Howlett, Ross, Samushia, Percival, Manera
Measure RSD in 2pt correlation function of 63k spec-z galaxies with z<0.2, an epoch where there are currently only limited measurements from SDSS7 Main sample. This sample, denoted MGS, covers 6k sq deg with z_eff=0.15 which concentrates on BAO measurements. In order to validate the fitting methods and derive errors, create and analyze 1000 mock catalogues using a new algorithm called PICOLA to generate accurate DM fields. Haloes are then selected using a FoF algorithm, and populated with galaxies using HOD fitted to the data. Fit a model to the monopole and quadrupole moments of the MGS correlation function, including both the RSD and AP effect, the latter of which results in anisotropic distortions if the wrong distance-redshift relation is used. This gives a measurement of f(z_eff) sigma8(z_eff)=0.53pm0.19. Assuming a fixed fiducial cosmology for the distance-z relationship based on recent Planck results, constraints on the growth rate tighten to f(z_eff) sigma8(z_eff)=0.44pm0.1. Combine measurement with recent CMB and BAO data allows constraint on the growth index of fluctuations, gamma. Assuming a BG LCDM cosmology, find gamma = 0.64pm0.09, which is consistent with the prediction of GR (gamma~0.55), though with a slight preference for higher gamma and hence models with weaker gravitational interactions.
1409.3242
The clustering of the SDSS DR7 Main Galaxy sample I: a 4 per cent distance measure at z=0.15
Ross, Samushia, Howlett, Percival, Burden, Manera
Create a sample of z<0.2 spec-z galaxies from SDSS DR7, covering 6813 sq deg. Galaxies are chosen to sample the highest mass haloes, with an effective bias of 1.5, allowing construction of 1000 mock galaxy catalogs, which is used to estimate statistical errors and test methods. Use an estimate of the gravitational potential to "reconstruct" the linear density fluctuations, enhancing BAO signal in the measured correlation function band PS. Fitting to these measurements, determine D(z_eff=0.15)=644pm25(rd/rd_fid) Mpc, this s a better than 4% distance measurement. This "fills the gap" in BAO distance ladder between previously measured local and higher z measurements, and affords significant improvement in constraining the properties of DE. Combining measurement with other BAO measurements from BOSS and 6dFGS galaxy samples provides a 15% improvement n the determination of the EoS of DE and the value of the Hubble parameter at z=0 (H0). Our measurement is fully consistent with the Planck results and the LCDM concordance cosmology, but increases the tension between Planck+BAO H0 determinations and direct H0 measurements.
1409.3364
Cosmological parameter constraints from CMB lensing with cosmic voids
Chantavat, Sawangwit, Sutter, Wandelt
Detecting a series of ~10 voids of size RV>20 Mpc/h along a LoS with 100-200 independent sq deg patches of the sky can potentially constrain cosmo parameters that are competitive with PLANCK alone. The chance of finding such patches are seemingly small. This analysis is based on current knowledge of the average void profiles and analytical estimates of the void number function in upcoming surveys. The full potential of this technique relies on an accurate determination of the void profile to ~10% level. CMB lensing with voids will provide a competitive and complimentary rout to parameter constraints for the next generation cosmo observations.
1409.3409
CosmoSIS: modula cosmological parameter estimation
Zuntz et al
Present a new framework for cosmo parameter estimation, CosmoSIS, designed to connect together, share, and advance development of inference tools across the community. Describe the modules already available in CosmoSIS, including CAMB, Planck, cosmic shear calculations, and a suite of samplers.
1409.3528
Gender-based systematics in HST proposal selection
Reid
Proposal success rates calculated for HST cycles 11 through 21 as a function of gender of the PI. In each cycle, proposals with male PIs have a higher success rate, with the disparity greatest for Cycles 12 and 18. The offsets are small enough that they might be ascribed to chance for any single cycle, but the consistent pattern suggests the presence of a systematic effect. Closer inspection of results from Cycles 19, 20 and 21 shows that the systematic difference does not appear to depend on the geographic origin of the proposal nor does it depend on the gender distribution on the review panels. Segregating proposals by the seniority of the PI, the success rates by gender for more recent graduates (Phd since 2000) are more closely comparable. There is also a correlation between success by gender and the average seniority of the review panel for Cycles 19, 20 but not 21. Discuss these results and some consequent changes to the proposal format and additions to the HST TAC orientation process.
Wednesday, September 10, 2014
Day 742
Thursday.
1409.2883
A uniform history for galaxy evolution
Steinhardt, Speagle
Recent observations indicate a remarkable similarity in the properties of evolving galaxies at fixed mass and redshift; possible that most galaxies may evolve with a common history encompassing star formation, quasar accretion, and eventual quiescence. Quantify this by defining a "synchronization timescale" for galaxies as a function of mass and z that characterizes the extent to which different galaxies of a common mass are evolving in the same matter at various cosmic epochs. Measure this synchronization timescale using 9 different SF galaxy observations from the literature and SDSS quasar observations spanning 0<z<6. This synchronization timescale is a constant, approximately 1.5 Gyr for all combinations of mass and time. Also find that the ratio between the stellar mass of galaxies turning off SF and BH mass mass of turnoff quasars is approximately 30:1, much lower than the 500:1 for quiescent galaxies at low redshift. As a result, propose a model in which the SF "main sequence", analogous quasar behavior, and other observations form a galactic evolution "main sequence", in which SF occurs earliest, followed by SMBH accretion, and feedback between the two are dominated by deterministic rather than stochastic processes.
1409.2900
Characterizing SL2S galaxy groups using the Einstein radius
Verdugo et al
Analyze Einstein radius theta_E and compare with the distance from the arcs to the center of the lens R_A. Find corruption between theta_E and R_A, but with large scatter. Find a weak evidence of anti-correlation between R_A and z, with log R_A=0.58pm0.06-0.04pm0.1z, suggesting a possible evolution of the Einstein radius with z, as previously reported. Results show that R_A is correlated with L and N (more luminous and richer groups have greater R_A), and a possible correlation between R_A and the N/L ratio. Analysis indicates that R_A is correlated with theta_E in the sample, making R_A useful to characterize properties like L and N in galaxy groups. Additionally, present evidence suggesting that the Einstein radius evolves with z.
1409.2883
A uniform history for galaxy evolution
Steinhardt, Speagle
Recent observations indicate a remarkable similarity in the properties of evolving galaxies at fixed mass and redshift; possible that most galaxies may evolve with a common history encompassing star formation, quasar accretion, and eventual quiescence. Quantify this by defining a "synchronization timescale" for galaxies as a function of mass and z that characterizes the extent to which different galaxies of a common mass are evolving in the same matter at various cosmic epochs. Measure this synchronization timescale using 9 different SF galaxy observations from the literature and SDSS quasar observations spanning 0<z<6. This synchronization timescale is a constant, approximately 1.5 Gyr for all combinations of mass and time. Also find that the ratio between the stellar mass of galaxies turning off SF and BH mass mass of turnoff quasars is approximately 30:1, much lower than the 500:1 for quiescent galaxies at low redshift. As a result, propose a model in which the SF "main sequence", analogous quasar behavior, and other observations form a galactic evolution "main sequence", in which SF occurs earliest, followed by SMBH accretion, and feedback between the two are dominated by deterministic rather than stochastic processes.
1409.2900
Characterizing SL2S galaxy groups using the Einstein radius
Verdugo et al
Analyze Einstein radius theta_E and compare with the distance from the arcs to the center of the lens R_A. Find corruption between theta_E and R_A, but with large scatter. Find a weak evidence of anti-correlation between R_A and z, with log R_A=0.58pm0.06-0.04pm0.1z, suggesting a possible evolution of the Einstein radius with z, as previously reported. Results show that R_A is correlated with L and N (more luminous and richer groups have greater R_A), and a possible correlation between R_A and the N/L ratio. Analysis indicates that R_A is correlated with theta_E in the sample, making R_A useful to characterize properties like L and N in galaxy groups. Additionally, present evidence suggesting that the Einstein radius evolves with z.
Tuesday, September 9, 2014
Day 741
Wednesday.
1409.1582
Minor vs major mergers: the stellar mass growth of massive galaxies from z=3 using number density selection techniques
Owensworth, Conselice, et al
Present a study on the stellar mass growth of the progenitors of local massive galaxies with a variety of number density selections with n<1e-4 Mpc^-3 (corresponding to M*=1e11.24 Msun at z=0.3) in 0.3<z<3.0. Select the progenitors of massive galaxies using a constant number density selection, and one which is adjusted to account for major mergers. Find that the progenitors of massive galaxies grow by a factor of four in total stellar mass over this redshift range. On average the stellar mass added via the processes of SF, major and minor mergers account for 24pm8%, 17pm15%, and 34pm14%, respectively, of the total galaxy stellar mass at z=0.3. Therefore 51pm20% of the total stellar mass in massive galaxies at z=0.3 is created externally to their z=3 progenitors. Explore the implication of these results on the cold gas accretion rate and size evolution of the progenitors of most massive galaxies over the same z range. Find an average gas accretion rate of ~66pm32 Msun/yr over 1.5<z<3.0. Find that the size evolution of a galaxy sample selected this way is on average lower than the findings of other investigations.
1409.2488
MUSE observations of the lensing cluster SMACSJ2031.8-4036: new constraints on the mass distribution in the cluster core
Richard, et al
Lensing cluster observation with MUSE IFS as part of its commissioning on VLT. MUSE ideally suited for identifying lensed galaxies in the cluster core, particularly in multiple-imaged systems. Perform z analysis of all sources in the data cube, identifying a total of 12 systems ranging from z=1.46 to z=6.4, with all images of each system confirmed by spectra. Allows accurate constraint on the cluster mass profile in this region. Possible Lya emitter discovery with future MUSE observation due to strong magnification and the high sensitivity of this instrument.
1409.2492
The fundamental plane of massive quiescent galaxies out to z~2
van de Sande, Kriek, Franx, Beyanson, van Dokkum
Find preliminary evidence for the existence of the FP out to z~2, but the scatter increases from z~0 to ~2, even when taking into account the larger measurement uncertainties at higher z. Find a strong evolution of the zero point from z~2 to 0. At z>1 find that the spectroscopic sample is bluer. Use the color offsets to estimate a M/L correction, which then the implied FP zero point evolution after correction is significantly smaller. This is consistent with an apparent formation redshift of z_form=6.6+3.2-1.4 for the underling population, ignoring the effete of progenitor bias. A more complete spectroscopic sample is required at z~2 to properly measure the M/L evolution from FP evolution.
1409.2506
On the role of GRBs on life extinction in the Universe
Piran, Jiminez
GRB can be a threat to life. Using recent determinations of the rate, LF, and host properties of GRBs, estimate the probability that a life-trheatening GRB would take place. Long GRBs are the most dangerous. A very good chance that at least one lethal GRB took place during the past 5Gyr close enough to Earth as to significantly damage life. 50% chance that such GRB took place in the last 500 Myr causing one of the major mass extinction events. Probability of lethal GRB is much larger in the inner MW (95% within a radius of 4kpc from the galactic center), making it inhospitable to life. At more than 10 kpc from galactic center, probability drops below 50%. Safest environment for life are the lowest density regions in the outskirts of large galaxies. Life can exist in only ~10% of galaxies [how did they determine that?]. A cosmological constant is essential for such systems to exist. Because both the higher GRB rate and galaxies being smaller, life as it exists on Earth could not take place at z>0.5. Early life forms must have been much more resilient to radiation.
1409.2750
Coming of age in the dark sector: how dark matter haloes grow their gravitational potential wells
van den Bosch, Jiang, Hearin, Campbell, Watson, Padmanabhan
Present a detailed study of how DM haloes assemble their mass and grow their (central) potential well. Characterize these via their mass accretion histories (MAHs) and potential well growth histories (PWGHs), which is extracted from the Bolshoi simulation and from SAM merger trees supplemented with a method to compute the maximum circular velocity, Vmax, of progenitor haloes. The results of both methods are in excellent agreement, both in terms of the average and the scatter. Show that MAH and PWGH are tightly correlated, and that growth of the central potential precedes the assembly of mass; the maximum circular velocity is already half the present day value by the time the halo has accreted only 2% of its final mass. Finally, demonstrate that MAHs have universal form, which is used to develop a new and improved universal model that can be used to compute the average or median MAH and PWGH for halo of any mass in any LCDM cosmology, without having to run a numerical simulation or a set of halo merger trees.
1409.2838
How the cosmic web induces intrinsic alignments of galaxies
Codis, Dubois, Pichon, Devriendt, Slyz
Direct measurements of IA seem to agree on a contamination at a level of a few % of the shear correlation functions, although the amplitude of the effect depends on the population of galaxies considered. Given this dependency, it is difficult to use DM-only sims as the sole resource to predict and control IA. Report estimates on the level of IA in cosmo-hydro sim Horizon-AGN. In particular, assuming that the spin of galaxies is a good proxy for their ellipticity, show how those spins are spatially correlated and how they couple to the tidal field in which they are embedded. Also present theoretical calculations that illustrate and qualitatively explain the observed signals.
1409.1582
Minor vs major mergers: the stellar mass growth of massive galaxies from z=3 using number density selection techniques
Owensworth, Conselice, et al
Present a study on the stellar mass growth of the progenitors of local massive galaxies with a variety of number density selections with n<1e-4 Mpc^-3 (corresponding to M*=1e11.24 Msun at z=0.3) in 0.3<z<3.0. Select the progenitors of massive galaxies using a constant number density selection, and one which is adjusted to account for major mergers. Find that the progenitors of massive galaxies grow by a factor of four in total stellar mass over this redshift range. On average the stellar mass added via the processes of SF, major and minor mergers account for 24pm8%, 17pm15%, and 34pm14%, respectively, of the total galaxy stellar mass at z=0.3. Therefore 51pm20% of the total stellar mass in massive galaxies at z=0.3 is created externally to their z=3 progenitors. Explore the implication of these results on the cold gas accretion rate and size evolution of the progenitors of most massive galaxies over the same z range. Find an average gas accretion rate of ~66pm32 Msun/yr over 1.5<z<3.0. Find that the size evolution of a galaxy sample selected this way is on average lower than the findings of other investigations.
1409.2488
MUSE observations of the lensing cluster SMACSJ2031.8-4036: new constraints on the mass distribution in the cluster core
Richard, et al
Lensing cluster observation with MUSE IFS as part of its commissioning on VLT. MUSE ideally suited for identifying lensed galaxies in the cluster core, particularly in multiple-imaged systems. Perform z analysis of all sources in the data cube, identifying a total of 12 systems ranging from z=1.46 to z=6.4, with all images of each system confirmed by spectra. Allows accurate constraint on the cluster mass profile in this region. Possible Lya emitter discovery with future MUSE observation due to strong magnification and the high sensitivity of this instrument.
1409.2492
The fundamental plane of massive quiescent galaxies out to z~2
van de Sande, Kriek, Franx, Beyanson, van Dokkum
Find preliminary evidence for the existence of the FP out to z~2, but the scatter increases from z~0 to ~2, even when taking into account the larger measurement uncertainties at higher z. Find a strong evolution of the zero point from z~2 to 0. At z>1 find that the spectroscopic sample is bluer. Use the color offsets to estimate a M/L correction, which then the implied FP zero point evolution after correction is significantly smaller. This is consistent with an apparent formation redshift of z_form=6.6+3.2-1.4 for the underling population, ignoring the effete of progenitor bias. A more complete spectroscopic sample is required at z~2 to properly measure the M/L evolution from FP evolution.
1409.2506
On the role of GRBs on life extinction in the Universe
Piran, Jiminez
GRB can be a threat to life. Using recent determinations of the rate, LF, and host properties of GRBs, estimate the probability that a life-trheatening GRB would take place. Long GRBs are the most dangerous. A very good chance that at least one lethal GRB took place during the past 5Gyr close enough to Earth as to significantly damage life. 50% chance that such GRB took place in the last 500 Myr causing one of the major mass extinction events. Probability of lethal GRB is much larger in the inner MW (95% within a radius of 4kpc from the galactic center), making it inhospitable to life. At more than 10 kpc from galactic center, probability drops below 50%. Safest environment for life are the lowest density regions in the outskirts of large galaxies. Life can exist in only ~10% of galaxies [how did they determine that?]. A cosmological constant is essential for such systems to exist. Because both the higher GRB rate and galaxies being smaller, life as it exists on Earth could not take place at z>0.5. Early life forms must have been much more resilient to radiation.
1409.2750
Coming of age in the dark sector: how dark matter haloes grow their gravitational potential wells
van den Bosch, Jiang, Hearin, Campbell, Watson, Padmanabhan
Present a detailed study of how DM haloes assemble their mass and grow their (central) potential well. Characterize these via their mass accretion histories (MAHs) and potential well growth histories (PWGHs), which is extracted from the Bolshoi simulation and from SAM merger trees supplemented with a method to compute the maximum circular velocity, Vmax, of progenitor haloes. The results of both methods are in excellent agreement, both in terms of the average and the scatter. Show that MAH and PWGH are tightly correlated, and that growth of the central potential precedes the assembly of mass; the maximum circular velocity is already half the present day value by the time the halo has accreted only 2% of its final mass. Finally, demonstrate that MAHs have universal form, which is used to develop a new and improved universal model that can be used to compute the average or median MAH and PWGH for halo of any mass in any LCDM cosmology, without having to run a numerical simulation or a set of halo merger trees.
1409.2838
How the cosmic web induces intrinsic alignments of galaxies
Codis, Dubois, Pichon, Devriendt, Slyz
Direct measurements of IA seem to agree on a contamination at a level of a few % of the shear correlation functions, although the amplitude of the effect depends on the population of galaxies considered. Given this dependency, it is difficult to use DM-only sims as the sole resource to predict and control IA. Report estimates on the level of IA in cosmo-hydro sim Horizon-AGN. In particular, assuming that the spin of galaxies is a good proxy for their ellipticity, show how those spins are spatially correlated and how they couple to the tidal field in which they are embedded. Also present theoretical calculations that illustrate and qualitatively explain the observed signals.
Monday, September 8, 2014
Day 740
Tuesday.
1409.1919
Neutral hydrogen in galaxy haloes at at the peak of the cosmic star formation history
Faucher-Giguere, Hopkins, Keres, Muratov, Quataert, Murray
Gas inflows and outflows regulate SF in galaxies. Probing these processes is one of the central motivations for spectroscopic measurements of the circum-galactic medium. Use high-resolution cosmological zoom-in simulations from the FIRE project to make predictions for the covering fractions of neutral hydrogen around galaxies at z=2-4. These simulations resolve the interstellar medium of galaxies and explicitly implement a comprehensive set of stellar feedback mechanisms. Simulation sample consists of 16 main halos covering the mass range Mh~2e9-8e12 Msun at z=2, including 12 haloes in the mass range Mh~1e11-1e12 Msun corresponding to LBGs. Process simulations with a ray tracing method to compute the ionization state of the gas. Galactic winds increase the HI covering fractions in galaxy haloes by direct ejection of cool gas from galaxies and through interactions with gas inflowing from the IGM. Simulations predict HI covering fraction for LLSs consistent with measurements around z~2-2.5 LBGs; these covering fractions are a factor ~2 higher than previous calculations without galactic winds. The fractions of HI absorbers arising in inflows and in outflows are on average ~50% but exhibit significant time variability. For the most massive halos, find a factor ~3 deficit in the LLS covering fraction relative to what is measured around quasars at z~2, suggesting that the presence of a quasar may affect the properties of halo gas on ~100 kpc scales. The predicted covering fractions peak at Mh~1e11-12 Msun, near the peak of the SF efficiency in DM haloes. In the simulations, SF and galactic outflows are highly time dependent; HI covering fractions are also time variable but less so because they represent averages over large areas.
1409.1924
The re-distribution of matter in the cores of galaxy clusters
Laporte, White
Present cosmo N-body sims of the assembly of BCGs in rich clusters. At z=2 populate DM sub haloes with self-gravitating stellar systems whose abundance and structure match observed high-z galaxies. By z=0, mergers have built much larger galaxies at cluster centre. Their DM density profiles are shallower than in corresponding DM-only simulations, but their total mass density profiles (stars + DM) are quite similar. Differences are found only at radii where the effects of central BHs may be significant. DM density slopes shallower than gamma=1.0 occur for r/r200<0.015, close to the half-light radii of the BCGs. Experiments up port earlier suggestions that NFW-like profiles are an attractor for the hierarchical growth of structure in collision less systems - total mass density profiles asymptote to the solution found in DM-only simulations over the radial range where mergers produce significant mixing between stars and DM. Simulated DM fractions are substantially higher in BCGs than in field ellpticals, reaching 80% within the HLR. Also estimate the SMBH mergers should create BCG cores as large as rc~3kpc. The good agreement of all these properties with recent observational studies of BCG structure suggests that dissipation processes have not played a dominant role in the assembly of the observed systems.
1409.1919
Neutral hydrogen in galaxy haloes at at the peak of the cosmic star formation history
Faucher-Giguere, Hopkins, Keres, Muratov, Quataert, Murray
Gas inflows and outflows regulate SF in galaxies. Probing these processes is one of the central motivations for spectroscopic measurements of the circum-galactic medium. Use high-resolution cosmological zoom-in simulations from the FIRE project to make predictions for the covering fractions of neutral hydrogen around galaxies at z=2-4. These simulations resolve the interstellar medium of galaxies and explicitly implement a comprehensive set of stellar feedback mechanisms. Simulation sample consists of 16 main halos covering the mass range Mh~2e9-8e12 Msun at z=2, including 12 haloes in the mass range Mh~1e11-1e12 Msun corresponding to LBGs. Process simulations with a ray tracing method to compute the ionization state of the gas. Galactic winds increase the HI covering fractions in galaxy haloes by direct ejection of cool gas from galaxies and through interactions with gas inflowing from the IGM. Simulations predict HI covering fraction for LLSs consistent with measurements around z~2-2.5 LBGs; these covering fractions are a factor ~2 higher than previous calculations without galactic winds. The fractions of HI absorbers arising in inflows and in outflows are on average ~50% but exhibit significant time variability. For the most massive halos, find a factor ~3 deficit in the LLS covering fraction relative to what is measured around quasars at z~2, suggesting that the presence of a quasar may affect the properties of halo gas on ~100 kpc scales. The predicted covering fractions peak at Mh~1e11-12 Msun, near the peak of the SF efficiency in DM haloes. In the simulations, SF and galactic outflows are highly time dependent; HI covering fractions are also time variable but less so because they represent averages over large areas.
1409.1924
The re-distribution of matter in the cores of galaxy clusters
Laporte, White
Present cosmo N-body sims of the assembly of BCGs in rich clusters. At z=2 populate DM sub haloes with self-gravitating stellar systems whose abundance and structure match observed high-z galaxies. By z=0, mergers have built much larger galaxies at cluster centre. Their DM density profiles are shallower than in corresponding DM-only simulations, but their total mass density profiles (stars + DM) are quite similar. Differences are found only at radii where the effects of central BHs may be significant. DM density slopes shallower than gamma=1.0 occur for r/r200<0.015, close to the half-light radii of the BCGs. Experiments up port earlier suggestions that NFW-like profiles are an attractor for the hierarchical growth of structure in collision less systems - total mass density profiles asymptote to the solution found in DM-only simulations over the radial range where mergers produce significant mixing between stars and DM. Simulated DM fractions are substantially higher in BCGs than in field ellpticals, reaching 80% within the HLR. Also estimate the SMBH mergers should create BCG cores as large as rc~3kpc. The good agreement of all these properties with recent observational studies of BCG structure suggests that dissipation processes have not played a dominant role in the assembly of the observed systems.
Sunday, September 7, 2014
Day 739
Monday.
1301.5067
Direct gravitational imaging of intermediate mass black holes in extragalactic haloes
Inoue, Rashkov, Silk, Madau
Propose to directly detect IMBHs by observing multiply imaged QSO-galaxy or gg LS systems in the submillimter bands with high angular resolution. The silhouette of an IMBH in the lensing galaxy halo would appear as either a monopole-like or a dipole-like variation at the scale of the Einstein radius against the Einstein ring of the dust-emitting region surrounding the QSO. Use a particle tagging technique to dynamically populate a MW-sized DM halo with BHs and show that the surface mass density and number density of IMBHs have power-law dependences on the distance from the center of the host halo if smoothed on a scale of ~1kpc. Most of the BHs orbiting close to the center are freely roaming as they have lost their DM hosts during infall due to tidal stripping. Next generation submillimter telescopes with high angular resolution (<0.3 max) will be capable of directly mapping such off-nuclear freely roaming IMBHs with a mass of ~1e6 Msun in a lending galaxy that harbors a O(1e9 Msun) mass SMBH in its nucleus.
1409.1578
The orthogonally aligned dark halo of an Edge-on lensing galaxy in the Hubble Frontier Fields: a challenge for modified gravity
Diego, Broadhurst, Benitez, Lim, Lam
8" cluster lensed image (tangential shear), symmetrically bend in the middle by an edge-on lenticular galaxy (secondary deflection). An opportunity to place relative strong constraints on the lensing effect of this galaxy. Model the stelar lensing contribution using the observed pixels belonging to the galaxy, in 2D, and add to this a standard parameterized dark halo component. Find combined total mass of 3e11 Msun, irrespective of the choice of parameters. ... Alternative theories of gravity where the radial dependence is modified to avoid the need for DM are challenged by this finding, since generically these must be tied to the baryonic component which here is a stellar disk oriented nearly orthogonally to the lensed image deflection.
1409.1640
The effect of macro model uncertainties on microlensing modelling of lensed quasars
Vernardos, Fluke
Microlensed quasars studied for structure of multiply imaged quasars, especially the accretion disc and central SMBH system. But the derived constraints on models are affected by large systematic errors in the macro models, the microlensing magnification maps, and the convolution with realistic disc profiles. Different macro models of galaxy lens can lead to different values of kappa and gamma. Strategies of mitigating the effect of Delta kappa, Delta gamma are discussed in order to understand and control this potential source of systematic errors in accretion disc constraints derived from microlensing.
1301.5067
Direct gravitational imaging of intermediate mass black holes in extragalactic haloes
Inoue, Rashkov, Silk, Madau
Propose to directly detect IMBHs by observing multiply imaged QSO-galaxy or gg LS systems in the submillimter bands with high angular resolution. The silhouette of an IMBH in the lensing galaxy halo would appear as either a monopole-like or a dipole-like variation at the scale of the Einstein radius against the Einstein ring of the dust-emitting region surrounding the QSO. Use a particle tagging technique to dynamically populate a MW-sized DM halo with BHs and show that the surface mass density and number density of IMBHs have power-law dependences on the distance from the center of the host halo if smoothed on a scale of ~1kpc. Most of the BHs orbiting close to the center are freely roaming as they have lost their DM hosts during infall due to tidal stripping. Next generation submillimter telescopes with high angular resolution (<0.3 max) will be capable of directly mapping such off-nuclear freely roaming IMBHs with a mass of ~1e6 Msun in a lending galaxy that harbors a O(1e9 Msun) mass SMBH in its nucleus.
1409.1578
The orthogonally aligned dark halo of an Edge-on lensing galaxy in the Hubble Frontier Fields: a challenge for modified gravity
Diego, Broadhurst, Benitez, Lim, Lam
8" cluster lensed image (tangential shear), symmetrically bend in the middle by an edge-on lenticular galaxy (secondary deflection). An opportunity to place relative strong constraints on the lensing effect of this galaxy. Model the stelar lensing contribution using the observed pixels belonging to the galaxy, in 2D, and add to this a standard parameterized dark halo component. Find combined total mass of 3e11 Msun, irrespective of the choice of parameters. ... Alternative theories of gravity where the radial dependence is modified to avoid the need for DM are challenged by this finding, since generically these must be tied to the baryonic component which here is a stellar disk oriented nearly orthogonally to the lensed image deflection.
1409.1640
The effect of macro model uncertainties on microlensing modelling of lensed quasars
Vernardos, Fluke
Microlensed quasars studied for structure of multiply imaged quasars, especially the accretion disc and central SMBH system. But the derived constraints on models are affected by large systematic errors in the macro models, the microlensing magnification maps, and the convolution with realistic disc profiles. Different macro models of galaxy lens can lead to different values of kappa and gamma. Strategies of mitigating the effect of Delta kappa, Delta gamma are discussed in order to understand and control this potential source of systematic errors in accretion disc constraints derived from microlensing.
Friday, September 5, 2014
Day 738
Friday.
1409.1218
Why z>1 radio-loud galaxies are commonly located in proto-clusters
Hatch et al
Distant powerful radio-loud AGN (RLAGN) tend to reside in dense environments and are commonly found in proto-clusters at z>1.3. Examine whether this occurs because RLAGN are hosted by massive galaxies, which preferentially reside in rich environments. Compare environments of powerful RLAGN at 1.3<z<3.2 from the CARLA survey to a sample of radio-quiet galaxies matched in mass and redshift. Find the environment s of RLAGN are significantly denser than those of radio-quiet galaxies, implying that not more than 50% of massive galaxies in this epoch can host powerful radio-loud jets. This is not an observational selection effect as we find no evidence to suggest it is easier to observe the radio emission when the galaxy resides in a dense environment. Therefore suggest that the dense Mpc-scale environment fosters the formation of a radio jet from an AGN. Show that the number density of potent RLAGN host galaxies is consistent with every >1e14 Msun cluster having experienced powerful radio-loud feedback of duration ~60Myr during 1.3<z<3.2. This feedback could heat the interacluster medium to the extent of 0.5-1 KeV per gas particle, which could limit the amount of gas available for further star formation in the proto-cluster galaxies.
1409.1225
Redshift space distortions in the effective field theory of large scale structures
Senatore, Zaldarriaga
Introduce a formalism, valid both for DM and collapsed objects, that allows description of z-space distortions in the context of EFT of LSS. Expressing density perturbations in z-space corresponds to performing a change of coordinates and the resulting expressions contain products of density perturbations and velocity fields evaluated at the same location. These terms are sensitive to non-perturbative short-distance physics and in order to correctly treat them, they need to be renormalized by adding suitable counter terms. Therefore more counter terms are required in z-space expressions compared to their real space analogs. In particular in the expression for the one-loop matter PS there are two new counter terms. Just as in real space, long wavelength displacements affect correlation functions in z-space and need to be resumed. Generalize the real space formulas for IR resumption to this case: the final expressions are conceptually similar but are more challenging to compute numerically due to their reduced symmetry.
1409.1228
First frontier field constraints on the cosmic star-formation rate density at z~10 - The impact of lensing shear on completeness of high-redshift galaxy samples
Oesch, ... van Dokkum, et al
Search HFF dataset of A2744 and its parallel field for z~10 sources to further refine the evolution of the cosmic SFR density at z>8. Independently confirm two images of the recently discovered triply-imated z~9.8 source by Zitrin+2014, and set an upper limit for similar z~10 galaxies with red colors of J_125-H_160>1.2 in the parallel field of A2744. Utilize extensive simulations to derive the effective selection volume of Lyman-break galaxies at z~10, both in the lensed cluster field and in the adjacent parallel field. Particular care is taken to include position-dependent lensing shear to accurately account for the expected sizes and morphologies of highly-magnified sources. Show that both source blending and shear reduce the completeness at a given observed magnitude in the cluster, particularly near the critical curves. These effects have a significant, but largely overlooked, impact on the detectability of high-z sources behind clusters, and substantially reduce the expected number of highly-magnified sources. The detections and limits from both pointings result in a SFRD which is higher by 0.4pm0.4 dex than previous estimates at z~10 from blank fields. Nevertheless, the combination of these new results with all other estimates remain consistent with a rapidly declining SFRD in the 170 Myr from z~8 to z~10 as predicted by cosmological simulations and DM halo evolution in LCDM. Once biases introduced by magnification dependent completeness are accounted for, the full six cluster and parallel FF program will be an extremely powerful new dataset to probe the evolution of the galaxy population at z>8 before the advent of JWST.
1409.1232
A size-duration trend for gamma-ray burst progenitors
Barnacka, Loeb
GRBs show a bimodal distribution of durations, separated at a duration of ~2s. Observations have confirmed the association of long GRBs with the collapse of massive stars. The origin of short GRBs is still being explored. Examine constraints on the emission region size in short and log GRBs detected by Fermi/GBM. Find that the emission region size during the prompt emission, R, and the burst duration, T_90, are consistent wit the relation R~c * T_90, for both long and short GRBs. Find the characteristic size for the prompt emission region to be ~2e10 cm ,and ~4e11 cm for short and long GRBs, respectively.
1409.1239
The triggering of starbursts in low-mass galaxies
Lelli, et al
Results suggest that the starburst is triggered either by past interactions/mergers between gas-rich dwarfs or bay direct gas infall from the IGM.
1409.1240
Stability of small-scale baryon perturbations during cosmological recombination
Venumadhav, Hirata
Study small-scale fluctuations (baryon pressure sound waves) in the baryon fluid during recombination. In particular, look at their evolution in the presence of relative velocities between baryons and photons on large scales (k~1e-1 /Mpc), which are naturally present during the era of decoupling. Previous work concluded that the fluctuations grow due to an instability of sound waves in a recombining plasma, but that the growth factor is small for typical cosmological models. These analyses model recombination in an inhomogeneous universe as a perturbation to the parameters of the homogenous solution. Show that for relevant wave numbers k>1e3 /Mpc, the dynamics are significantly altered by the transport of both ionizing continuum (h nu > 13.6 eV) and Lyman-alpha photons between crests and troughs of the density perturbations. Solve the radiative transfer of photons in both these frequency ranges and incorporate the results in a perturbed 3-level atom model. Conclude that the instability persists at intermediate scales. Use the results to estimate a distribution of growth rates in 1e7 random realizations of large-scale relative velocities. Results indicate that there is no appreciable growth; out of these 1e7 realizations, the maximum growth factor we find is less than ~1.2 at wave numbers of k~1e3 /Mpc.
1409.1254
Strong lens time delay challenge: II. results of TDC1
Liao, Treu, Marshall, et al
Present the results of the first SL TDC. Present the main challenge, TDC1, consisting in analyzing thousands of simulated light curves blindly. Observational properties of the light curves cover the range in quality obtained for current targeted efforts (e.g. COSMOGRAIL) and expected from future synoptic surveys (LSST), and include "evilness" in the form of simulated systematic errors. 7 teams participated in TDC1, submitting results from 78 different method variants. After describing each method, compute and analyze basic statistics measuring accuracy (or bias) A, goodness of fit chisq, precision P, and success rate f. For some methods, identify outliers as an important issue. Other methods show that outliers can be controlled via visual inspection or conservative quality control. Several methods are competitive, i.e. give |A|<0.03, P<0.03, and chisq<1.5, with some of the methods already reaching sub-percent accuracy. The fraction of light curves yielding a time delay measurement is typically in the range f=20-40%. It depends strongly on the quality of the data: COSMOGRAIL-quality cadence and light curve lengths yield significantly higher f than does sparser sampling. Estimate that LSST should provide around 400 robust time-delay measurements, each with P<0.03 and |A|<0.01, comparable to current lens modeling uncertainties. In terms of observing strategies, find that A and f depend mostly on season length, while P depends mostly on cadence and campaign duration.
1409.1218
Why z>1 radio-loud galaxies are commonly located in proto-clusters
Hatch et al
Distant powerful radio-loud AGN (RLAGN) tend to reside in dense environments and are commonly found in proto-clusters at z>1.3. Examine whether this occurs because RLAGN are hosted by massive galaxies, which preferentially reside in rich environments. Compare environments of powerful RLAGN at 1.3<z<3.2 from the CARLA survey to a sample of radio-quiet galaxies matched in mass and redshift. Find the environment s of RLAGN are significantly denser than those of radio-quiet galaxies, implying that not more than 50% of massive galaxies in this epoch can host powerful radio-loud jets. This is not an observational selection effect as we find no evidence to suggest it is easier to observe the radio emission when the galaxy resides in a dense environment. Therefore suggest that the dense Mpc-scale environment fosters the formation of a radio jet from an AGN. Show that the number density of potent RLAGN host galaxies is consistent with every >1e14 Msun cluster having experienced powerful radio-loud feedback of duration ~60Myr during 1.3<z<3.2. This feedback could heat the interacluster medium to the extent of 0.5-1 KeV per gas particle, which could limit the amount of gas available for further star formation in the proto-cluster galaxies.
1409.1225
Redshift space distortions in the effective field theory of large scale structures
Senatore, Zaldarriaga
Introduce a formalism, valid both for DM and collapsed objects, that allows description of z-space distortions in the context of EFT of LSS. Expressing density perturbations in z-space corresponds to performing a change of coordinates and the resulting expressions contain products of density perturbations and velocity fields evaluated at the same location. These terms are sensitive to non-perturbative short-distance physics and in order to correctly treat them, they need to be renormalized by adding suitable counter terms. Therefore more counter terms are required in z-space expressions compared to their real space analogs. In particular in the expression for the one-loop matter PS there are two new counter terms. Just as in real space, long wavelength displacements affect correlation functions in z-space and need to be resumed. Generalize the real space formulas for IR resumption to this case: the final expressions are conceptually similar but are more challenging to compute numerically due to their reduced symmetry.
1409.1228
First frontier field constraints on the cosmic star-formation rate density at z~10 - The impact of lensing shear on completeness of high-redshift galaxy samples
Oesch, ... van Dokkum, et al
Search HFF dataset of A2744 and its parallel field for z~10 sources to further refine the evolution of the cosmic SFR density at z>8. Independently confirm two images of the recently discovered triply-imated z~9.8 source by Zitrin+2014, and set an upper limit for similar z~10 galaxies with red colors of J_125-H_160>1.2 in the parallel field of A2744. Utilize extensive simulations to derive the effective selection volume of Lyman-break galaxies at z~10, both in the lensed cluster field and in the adjacent parallel field. Particular care is taken to include position-dependent lensing shear to accurately account for the expected sizes and morphologies of highly-magnified sources. Show that both source blending and shear reduce the completeness at a given observed magnitude in the cluster, particularly near the critical curves. These effects have a significant, but largely overlooked, impact on the detectability of high-z sources behind clusters, and substantially reduce the expected number of highly-magnified sources. The detections and limits from both pointings result in a SFRD which is higher by 0.4pm0.4 dex than previous estimates at z~10 from blank fields. Nevertheless, the combination of these new results with all other estimates remain consistent with a rapidly declining SFRD in the 170 Myr from z~8 to z~10 as predicted by cosmological simulations and DM halo evolution in LCDM. Once biases introduced by magnification dependent completeness are accounted for, the full six cluster and parallel FF program will be an extremely powerful new dataset to probe the evolution of the galaxy population at z>8 before the advent of JWST.
1409.1232
A size-duration trend for gamma-ray burst progenitors
Barnacka, Loeb
GRBs show a bimodal distribution of durations, separated at a duration of ~2s. Observations have confirmed the association of long GRBs with the collapse of massive stars. The origin of short GRBs is still being explored. Examine constraints on the emission region size in short and log GRBs detected by Fermi/GBM. Find that the emission region size during the prompt emission, R, and the burst duration, T_90, are consistent wit the relation R~c * T_90, for both long and short GRBs. Find the characteristic size for the prompt emission region to be ~2e10 cm ,and ~4e11 cm for short and long GRBs, respectively.
1409.1239
The triggering of starbursts in low-mass galaxies
Lelli, et al
Results suggest that the starburst is triggered either by past interactions/mergers between gas-rich dwarfs or bay direct gas infall from the IGM.
1409.1240
Stability of small-scale baryon perturbations during cosmological recombination
Venumadhav, Hirata
Study small-scale fluctuations (baryon pressure sound waves) in the baryon fluid during recombination. In particular, look at their evolution in the presence of relative velocities between baryons and photons on large scales (k~1e-1 /Mpc), which are naturally present during the era of decoupling. Previous work concluded that the fluctuations grow due to an instability of sound waves in a recombining plasma, but that the growth factor is small for typical cosmological models. These analyses model recombination in an inhomogeneous universe as a perturbation to the parameters of the homogenous solution. Show that for relevant wave numbers k>1e3 /Mpc, the dynamics are significantly altered by the transport of both ionizing continuum (h nu > 13.6 eV) and Lyman-alpha photons between crests and troughs of the density perturbations. Solve the radiative transfer of photons in both these frequency ranges and incorporate the results in a perturbed 3-level atom model. Conclude that the instability persists at intermediate scales. Use the results to estimate a distribution of growth rates in 1e7 random realizations of large-scale relative velocities. Results indicate that there is no appreciable growth; out of these 1e7 realizations, the maximum growth factor we find is less than ~1.2 at wave numbers of k~1e3 /Mpc.
1409.1254
Strong lens time delay challenge: II. results of TDC1
Liao, Treu, Marshall, et al
Present the results of the first SL TDC. Present the main challenge, TDC1, consisting in analyzing thousands of simulated light curves blindly. Observational properties of the light curves cover the range in quality obtained for current targeted efforts (e.g. COSMOGRAIL) and expected from future synoptic surveys (LSST), and include "evilness" in the form of simulated systematic errors. 7 teams participated in TDC1, submitting results from 78 different method variants. After describing each method, compute and analyze basic statistics measuring accuracy (or bias) A, goodness of fit chisq, precision P, and success rate f. For some methods, identify outliers as an important issue. Other methods show that outliers can be controlled via visual inspection or conservative quality control. Several methods are competitive, i.e. give |A|<0.03, P<0.03, and chisq<1.5, with some of the methods already reaching sub-percent accuracy. The fraction of light curves yielding a time delay measurement is typically in the range f=20-40%. It depends strongly on the quality of the data: COSMOGRAIL-quality cadence and light curve lengths yield significantly higher f than does sparser sampling. Estimate that LSST should provide around 400 robust time-delay measurements, each with P<0.03 and |A|<0.01, comparable to current lens modeling uncertainties. In terms of observing strategies, find that A and f depend mostly on season length, while P depends mostly on cadence and campaign duration.
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