Friday after Christmas.
1412.7719
How are is the Bullet Cluster (in a $\Lambda$CDM universe)?
Kraljic, Sarkar
Consider the expected number of Bullet-like systems on the sky up to a specified redshift, which allows for direct comparison with observations. Using a Hubble volume N-body simulation with high resolution, investigate how the number of such systems depends on the masses of the halo pairs, their separations, and collision angle. This enables extraction of an approximate formula for the expected number of halo-halo collisions given specific collisional parameters. Use extreme value statistics to analyze the tail of the pairwise velocity distribution and demonstrate that it is fatter than the previously assumed Gaussian form. Estimate that the number of DM halo pairs as or more extreme than the Bullet cluster is 1.3+2.0-0.6 up to z=0.3. The discovery of more such systems would thus be a challenge to the standard cosmology.
Thursday, December 25, 2014
Wednesday, December 24, 2014
Day 807
Wednesday. Then Christmas.
1412.7162
PRIMUS: galaxy environment on the quiescent fraction evolution at z<0.8
Hahn, et al
Investigate the effects of galaxy environment on the evolution of the quiescent fraction ($f_\mathrm{Q}$) from z=0.8 to 0.0 using spectroscopic redshifts and multi-wavelength imaging data from the PRIsm Multi-Object Survey (PRIMUS) and the SDSS. The stellar mass limited galaxy sample consists of ~14k PRIMUS galaxies within 0.2<z<0.8 and ~64k SDSS galaxies of 0.05<z<0.12. Classify the galaxies as quiescent or star-forming based on an evolving specific SF cut, and as low or high density environments based on fixed cylindrical aperture environment measurements on a volume-limited environment defining population. For quiescent and SF galaxies in low or high density environments, examine the evolution of their SMF. Then using the SMFs, compute $f_Q(M*)$ and quantify its evolution within the redshift range. Find that the quiescent fraction is higher at higher masses and in denser environments. The quiescent fraction rises with cosmic time for all masses and environments. At a fiducial mass of 1e10.5 Msun, for 0.1<z<0.7, the quiescent fraction rises by 15% at the lowest environments and by 25% at the highest environments measured. These results suggest that for a minority of galaxies their cessation of SF is due to external influences on them. However, in the recent Universe a substantial fraction of the galaxies that cease forming stars do so due to internal processes.
1412.7521
A measurement of gravitational lensing of the cosmic microwave background by galaxy clusters using data from the South Pole Telescope
Baxter, et al
Stat error ~ sys error, so attempt no correction. 513 clusters selected via their SZ signatures in SPT data. Rule out null hypothesis of no lensing at 3.0 sigma. The lensing-derived mass estimate fro the full cluster sample is consistent with that inferred from the SZ flux: M200,lens = 0.76pm0.36 M200,SZ (68% CL, stat error only).
PRIMUS: galaxy environment on the quiescent fraction evolution at z<0.8
Hahn, et al
Investigate the effects of galaxy environment on the evolution of the quiescent fraction ($f_\mathrm{Q}$) from z=0.8 to 0.0 using spectroscopic redshifts and multi-wavelength imaging data from the PRIsm Multi-Object Survey (PRIMUS) and the SDSS. The stellar mass limited galaxy sample consists of ~14k PRIMUS galaxies within 0.2<z<0.8 and ~64k SDSS galaxies of 0.05<z<0.12. Classify the galaxies as quiescent or star-forming based on an evolving specific SF cut, and as low or high density environments based on fixed cylindrical aperture environment measurements on a volume-limited environment defining population. For quiescent and SF galaxies in low or high density environments, examine the evolution of their SMF. Then using the SMFs, compute $f_Q(M*)$ and quantify its evolution within the redshift range. Find that the quiescent fraction is higher at higher masses and in denser environments. The quiescent fraction rises with cosmic time for all masses and environments. At a fiducial mass of 1e10.5 Msun, for 0.1<z<0.7, the quiescent fraction rises by 15% at the lowest environments and by 25% at the highest environments measured. These results suggest that for a minority of galaxies their cessation of SF is due to external influences on them. However, in the recent Universe a substantial fraction of the galaxies that cease forming stars do so due to internal processes.
1412.7521
A measurement of gravitational lensing of the cosmic microwave background by galaxy clusters using data from the South Pole Telescope
Baxter, et al
Stat error ~ sys error, so attempt no correction. 513 clusters selected via their SZ signatures in SPT data. Rule out null hypothesis of no lensing at 3.0 sigma. The lensing-derived mass estimate fro the full cluster sample is consistent with that inferred from the SZ flux: M200,lens = 0.76pm0.36 M200,SZ (68% CL, stat error only).
Tuesday, December 23, 2014
Day 806
Monday. Tuesday.
1412.6916
Gravitational lensing - Einstein's Unfinished Symphony
Treu, Ellis
Gravitational lensing - the deflection of light rays by gravitating matter - has become a major tool of modern cosmologist. Proposed nearly a hundred years ago as a key feature of Einstein's theory of GR, trace the historical development since its verification at a solar eclipse in 1919. Einstein was apparently cautious about its practical utility and the subject lay dormant observationally for nearly 60 years. Nonetheless there has been rapid progress over the past 20 years. The technique allows astronomers to chart the distribution of DM on large and small scales thereby testing predictions of the standard cosmological model which assumes DM comprises a massive weakly-interacting particle. By measuring distances and tracing the growth of DM structure over cosmic time, gravitational lensing also holds great promise in determining whether the DE, postulated to explain the accelerated cosmic expansion is a vacuum energy density or a failure of GR on large scales. Illustrate the wide range of applications which harness the power of gravitational lensing, from searches for the earliest galaxies magnified by massive clusters to those for extrasolar planets which temporarily brighten a background star. Summarize the future prospects with dedicated ground and space-based facilities designed to exploit this remarkable physical phenomenon.
1412.6916
Gravitational lensing - Einstein's Unfinished Symphony
Treu, Ellis
Gravitational lensing - the deflection of light rays by gravitating matter - has become a major tool of modern cosmologist. Proposed nearly a hundred years ago as a key feature of Einstein's theory of GR, trace the historical development since its verification at a solar eclipse in 1919. Einstein was apparently cautious about its practical utility and the subject lay dormant observationally for nearly 60 years. Nonetheless there has been rapid progress over the past 20 years. The technique allows astronomers to chart the distribution of DM on large and small scales thereby testing predictions of the standard cosmological model which assumes DM comprises a massive weakly-interacting particle. By measuring distances and tracing the growth of DM structure over cosmic time, gravitational lensing also holds great promise in determining whether the DE, postulated to explain the accelerated cosmic expansion is a vacuum energy density or a failure of GR on large scales. Illustrate the wide range of applications which harness the power of gravitational lensing, from searches for the earliest galaxies magnified by massive clusters to those for extrasolar planets which temporarily brighten a background star. Summarize the future prospects with dedicated ground and space-based facilities designed to exploit this remarkable physical phenomenon.
Friday, December 19, 2014
Day 805
Monday, Tuesday, Wednesday, Thursday.
1412.3851
Fourier band-power E/B-mode estimators for cosmic shear
Becker, Rozo
New Fourier band-power estimators for cosmic shear analysis and E/B-mode separation. Consider both the case where one performs E/B mode separation and the case where one does not. The resulting estimators have several nice properties which make them idea for comic shear analysis. First, they can be written as linear combinations of the binned cosmic shear correlation functions. Second, they account for the survey window function in real space. Third, they are unbiased by shape noise since they do not use correlation function data at zero separation. Fourth, the band-power functions in Fourier space are compact and largely non-oscillatory. Fifth, they can be used to construct band-power estimators with very efficient data compression properties. In particular, find that all of the information on the parameters Omega_m, sigma8 and n_s in the shear correlation functions in the range of 10'-400' for single tomographic bin can be compressed into only 3 band-power estimates. Lastly, can achieve these rates of data compression while excluding small-scale information where the modeling of the shear correlation functions and power spectra is very difficult. Given these desirable properties, these estimators will be very useful for cosmic shear data analysis.
1412.3854
Designing an inflation galaxy survey: how to measure $\sigma(f_{\rm NL}) \sim 1$ using scale-dependent galaxy bias
de Putter, Doré
BAO surveys require spectroscopic redshifts; to optimize the f_NL^loc measurement, a deep, wide, multi-band imaging survey is preferred. For sigma(f_NL^loc)~1, need i-band AB magnitude depth of i~23, number density ~8/arcmin^2, and a modest photo-z accuracy sigma(z)/(1+z)<0.1, and the ability to measure stellar mass with a precaution ~0.2 dex or better (or another proxy for halo mass with equivalent scatter). Even stronger constraints can potentially be obtained with the galaxy bispectrum.
1412.3862
Why do galaxies stop forming stars? I. The passive fraction - black hole mass relation for central galaxies
Bluck, et al
400k SDSS galaxies at z<0.2: find a strong dependence of the passive fraction on BH mass, which is largely unaffected by the details of the BH mass estimate. Moreover, the passive fraction relationship with BH mass remains strong and tight even at fixed values of galaxy mass M*, DM halo mass Mhalo, and bulge-to-total stellar mass ratio (B/T). The passive fraction dependence on M*, Mhalo and B/T is weak at fixed MBH. These observations show that, for central galaxies, MBH is the strongest correlation with the passive fraction, consistent with quenching from AGN feedback.
1412.3866
Two-size approximation: a simple way of treating the evolution of grain is distribution in galaxies
Hirashita
Propose a simple model of dust enrichment in a galaxy with a simplified treatment of grain size distribution by imposing a `two-size approximation'; that is, all the grain population is represented by small (grain radius a<0.03 um) and large (a>0.03um) grains. Include in the model dust supply from stellar ejecta, destruction in supernova shocks, dust growth by accretion, grain growth by coagulation and grain disruption by shattering, considering how these processes work on the small and large grains. Show that this simple framework reproduces the main features found in full calculations of grain size distributions as follows. The dust enrichment starts with the supply of large grains from stars. At a metallicity level referred to as the critical metallicity of accretion, the abundance of the small grains formed by shattering becomes large enough to rapidly increase the grain abundance by accretion. Associated with the epoch, the mass ratio of the small grains to the large grains reaches the maximum. After that, this ratio converges to the value determined by the balance between shattering and coagulation, and the dust-to-metal ratio is determined by the balance between accretion and shock destruction. With a MC sim, demonstrate that the simplicity of the model has an advantage in predicting statistical properties. Also show some applications for predicting observational dust properties such as extinction curves.
1412.4009
Cross-correlation of near and far-infrared background anisotropies as traced by Spitzer and Herschel
Thacker, et al
Hershel (FIR): 250, 350, 500um; Spitzer: 3.6 um. The cross-correlation between them are detected such that the correlation coefficient at 10' angular scales decreases from 0.3 to 0.1 when the FIR wavelength increases from 250 to 500 um. Model the cross-correlation using a halo model with 3 components: (a) FIR bright or dusty SF galaxies below the masking depth in Herschel maps, (b) NIR faint galaxies below the masking depth at 3.6 um, and (c) intra-halo light, or diffuse stars in DM haloes, that likely dominates fluctuations at 3.5 um. The model is able to reasonably reproduce the autocorrelations at each of the FIR wavelengths and 3.6 um and their corresponding cross-correlations. While the FIR and NIR auto-correlations are dominated by faint dusty, SF galaxies and intra-halo light, respectively, find that roughly half of the cross correlation between NIR and FIR backgrounds is due to the same galaxies that remain unmasked at 3.6 um. The remaining signal in the cross-correlation is due to intra-halo light present in the same DM haloes as those hosting the same faint and unmasked galaxies. In this model, the decrease in the cross-correlation signal from 250um to 500 um comes from the fact that the galaxies that are primarily contributing to 500 um fluctuations peak at a higher redshift than those at 250 um.
1412.4121
Deciphering the 3D structure of the old galactic bulge from the OGLE RR Lyrae stars
Pietrukowicz, et al
Analyzed a sample of 27k fundamental-mode RR Lyrae variable stars (type RRab) detected toward the Galactic bulge by the OGLE survey. The data support that these metal-poor stars trace closely the barred structure formed of intermediate-age red clump giants. The distance to the Galactic center (GC) inferred from the bulge RR Lyrae stars is R_0=8.27pm0.01(stat)pm0.40(sys) kpc. Show that their spatial distribution has the shape of a triaxial ellipsoid with the major axis located in the Galactic plane and inclined at an angle i=20pm3 deg to the Sun-GC line of sight. The obtained scale-length ratio of the major axis to the minor axis in the Galactic plane, and to the axis vertical to the plane is 1:0.49:0.39. We do not see the evidence for the bulge RR Lyrae stars forming an X-shaped structure. Based on the light curve parameters, derive metallicities of the RRab variables and show that there is a very mild but statistically significant radial metallicity gradient. About 60% of the bulge RRab stars form 2 very close sequences on the period-amplitude (or Bailey) diagram, which is interpreted as two major old bulge populations: A and B. Their metallicities likely differ. Population A is about 4 times less abundant than the slightly more metal-poor population B. Most of the remaining stars seem to represent other, even more metal-poor populations of the bulge. The presence of multiple old populations indicates that the MW bulge was initially formed through mergers.
1412.4454
Probing gravity at large scales through CMB lensing
Pullen, Alam, Ho
Describe a methodology to probe gravity with the CMB lensing convergence kappa, specifically by measuring E_G, the ratio of the Laplacian of the gravitational scalar potential difference with the peculiar velocity divergence. Using kappa from CMB lensing as opposed to gg lensing avoids IA while also lacking a hard limit on the lens redshift or significant uncertainties in the source plane. Model E_G for general relativity and modified gravity, finding that E_G for f(R) gravity should be scale-dependent due to the scale-dependence of the growth rate f. Next, construct an estimator for E_G in terms of the lensing convergence-galaxy and galaxy angular power spectra, along with the RSD parameter beta. Also forecast statistical errors of E_G from the current Planck CMB lensing map and the CMASS and LOWZ spectroscopic galaxy samples measured from the BOSS survey, as well as BOSS spectroscopic quasars, from SDSS DR11. Expect this experimental configuration to detect E_G at the level of 11 sigma with CMASS/LOWZ galaxies alone and 13 sigma when BOSS quasars are included. Also find that both upcoming spectroscopic and photometric surveys, each set combined with the final Planck lensing map, can measure precisely both the redshift- and scale-dependence of E_G out to z=2 and higher, with photometric surveys having an advantage due to their large survey areas and high number densities. Finally, advanced ACTPol CMB lensing cross-correlated with spectroscopic (photometric) surveys can differentiate between GR and modified gravity at the level of 3 sigma (13 sigma). Performing a <1% measurement of E_G requires precision in beta on the order of 10%, which is currently achievable with a spectroscopic survey but will be difficult with only a photometric survey.
1412.4606
Intrinsic size correlations in weak lensing
Ciarlariello, Crittenden, Pace
Present a simple model for describing intrinsic correlations for galaxy sizes based on the halo model. Studying these correlations is important both to improve the understanding of galaxy properties and because it is an important potential systematic for WL magnification measurements. The model assumes that the density field drives these intrinsic correlations; also model the distribution of satellite galaxies. Calculate the possible contamination to measurements of lensing convergence PS from galaxy sizes, and show that the cross-correlation of intrinsic sizes with convergence is potentially an important systematic. Also explore how these intrinsic size correlations may affect surveys with different z depth. Find that, in this simple approach, intrinsic size correlations cannot be neglected in order to estimate lensing convergence PS for constraining cosmo parameters.
1412.4727
Optimizing BAO measurements with non-linear transformations of Lyman-alpha forest
Wang, Font-Ribera, Seljak
Explore the effect of applying a NL transformation to the Lyman-a forest transmitted flux F=exp(-tau) and the ability of analytic models to predict the resulting clustering amplitude. Both the large-scale bias of the transformed field (signal) and the amplitude of small scale fluctuations (noise) can be arbitrarily modified, but were unable to find a transformation that increases significantly the S/N ratio on large scales using Taylor expansion to 3rd order. Achieve a 33% improvement in S/N for Gaussianized field in traverse direction. On the other hand, explore analytic model for the large-scale biasing of the Lya forest, and present an extension of this model to describe the biasing of the transformed fields. Using hydrodynamic simulations, show that the model works best to describe the biasing wrt velocity gradients, but is less successful in prediction the biasing wrt large-scale density fluctuations, especially for very NL transformations.
1412.4760
A measurement of the cosmic microwave background gravitational lensing potential from 100 square degrees of SPTpol data
Story, et al
100 sq deg coverage, arc minute resolution at 150 GHz. Using a quadratic estimator, make maps of the CMB lensing potential from combinations of CMB temperature and polarization maps. Combine these lensing potential maps to form a minimum-variance (MV) map. The lensing potential is measured with a S/N ratio of greater than one for angular multipoles between 100<L<250. This is the highest S/N mass map made from CMB to date and will be powerful in cross-correlation with other tracers of large-scale structure. Calculate the PS of the lensing potential for each estimator, and report the value of the MV PS between 100<L<2000 as the primary result. Constrain the ratio of the spectrum to a fiducial LCDM model to be A_MV=0.92. Restricting to polarized data only, find A_POL=0.93. This measurement rejects the hypothesis of no lensing at 5.8 sigma using polarization data alone, and at 14 sigma using both temperature and polarization data.
1412.4781
Measuring primordial non-Gaussianity in the galaxy power spectrum: general relativity makes a difference
Camera, Santos, Maartens
In order to reduce the errors on f_NL, need to include measurements on the largest possible scales. Failure to include the relativistic effects on these scales can introduce significant bias in the best-fit value of f_NL.
1412.4867
Searching for extraterrestrial intelligence with the square kilometer array
Siemion et al
SKA could permit the most sensitive and exhaustive search for technologically-produced radio emission from advanced extraterrestrial intelligence (SETI) ever performed. For example, SKA1-MID will be capable of detecting a source roughly analogous to terrestrial high-power radars (e.g. air rout surveillance or ballistic missile warning radars, EIRP (=equivalent isotropic radiated power, ~1e17 erc/sec) at 10 pc in less than 15 minutes, and with a modest 4 beam SETI observing system could, in one minute, search every star in the primary beam out to ~100 pc for radio emission comparable to that emitted by the Aracibo Planetary Radar (EIRP~2e20 erg/sec). The flexibility of the signal detection systems used for SETI searches with the SKA will allow new algorithms to be employed that will provide sensitivity to a much wider variety of signal types than previously searched for. Discuss the astrobiological and astrophysical motivations for radio SETI and describe how the technical capabilities of the SKA will explore the radio SETI parameter space. Detail several conceivable SETI experimental programs on all components of SKA1, including commensal, primary-user, targeted and survey programs and project the enhancements to them possible with SKA2. Also discuss target selection criteria for these programs, and in the case of commensal observing, how the varied use cases of other primary observers can be used to full advantage for SETI.
1412.4914
Errors on errors - estimating cosmological parameter covariance
Joachimi, Taylor
Current and forthcoming cosmological data analyses share the challenge of huge datasets alongside increasingly tight requirements on the precision and accuracy of extracted cosmological parameters. The community is becoming increasingly aware that these requirements not only apply to the central values of parameters but, equally important, also to the error bars. Due to NL effects in the astrophysics, the instrument, and the analysis pipeline, data covariance matrices are usually not well known a priori and need to be estimated from the data itself, or from suites of large simulations. In either case, the finite number of realizations available to determine data covariances introduces significant biases and additional variance in the errors on cosmological parameters in a standard likelihood analysis. Review recent work on quantifying these biases and additional variances and discuss approaches to remedy these effects.
1412.5172
Neglecting primordial non-Gaussianity threatens future cosmological experiment accuracy
Camera et al
As the title says [abstract gives no more details].
1412.5186
Mesh-free free-form lensing I: methodology and application to mass reconstruction
Merten
Many applications and algorithms in the field of gravitational lensing make use of meshes with a finite number of nodes to analyze and manipulate data. Specific examples in lensing are astronomical CCD images in general, the reconstruction of density distributions from lensing data, lens-source plane mapping or the characterization and interpolation of a PSF. Present a numerical framework to interpolate and differentiate in the mesh-free domain, defined by nodes with coordinates that follow no regular pattern. The framework is based on radial basis functions (RBFs) to smoothly represent data around the nodes. Demonstrate the performance of Gaussian RBF-based, mesh-free interpolation and differentiation, which reaches the sub-percent level in both cases. Use the newly developed framework to translate ideas of non-parametric mass reconstruction from lensing onto the mesh-free domain. The method uses WL and SL constraints and ideally follows the distribution of input data. By reconstruction a simulated mock lens, find that strong-lensing only reconstructions achieve <10% accuracy in the areas where these constraints are available but provide poorer results when departing from these regions. WL only reconstructions give <10% accuracy outside the SL regime, but cannot resolve the inner core structure of the lens. Once both regimes are combined, accurate reconstructions can be achieved over the full field of view and with a spatial resolution which is optimally adapted to the input data.
1412.5584
The stellar mass - halo mass relation from galaxy clustering in VUDS: a high star formation efficiency at z~3
Durkalec, Le Févre, et al
The relation between the galaxy stellar mass M* and the DM halo mass M_h gives important information on the efficiency in forming stars and assembling stellar mass in galaxies. Present the stellar mass to halo mass ratio (SMHR) measurements at 2<z<5, obtained from the VIMOS Ultra Deep Survey. Use HOD modeling of clustering measurements on ~3000 galaxies with spectroscopic redshifts to derive the DM halo mass M_h, and SED fitting over a large set of multi-wavelength data to derive the stellar mass M* and compute the SMHR=M*/M_h. Find that the SMHR ranges from 1% to 2.5% for galaxies with M*=1.3e9 Msun to M*=7.4e9 Msun in DM haloes with M_h=1.3e11 Msun to M_h=3e11 Msun. Derive the integrated SF efficiency (ISFE) of these galaxies and find that the SF efficiency is a moderate 6-9% for lower mass galaxies while it is relatively high at 16% for galaxies with median stellar mass of the sample 7e9 Msun. The lower ISFE at lower masses may indicate that some efficient means of suppressing SF is at work (e.g., SNe feedback), while the high ISFE for the average galaxy at z~3 is indicating that these galaxies are efficiently building -up their stellar mass at a key epoch in the mass assembly process. Further infer that the average mass galaxy at z~3 will start experiencing SF quenching within a few hundred million years.
1412,5593
Deconstructing thermal Sunyaev-Zel'dovich - gravitational lensing cross-correlations: implications for the intracluster medium
Battaglia, Hill, Murray
Using hydro sims, show that these cross-correlation signals are dominated by contributions from hot gas in the ICM, rather than diffuse, unbound gas located beyond the viral radius (the "missing baryons"). Thus, these cross-correlations offer a tool with which to study the ICM over a wide range of halo masses and redshifts. In particular, show that the tSZ-CMB lensing cross-correlation is more sensitive to gas in lower-mass, higher-redshift halos and gas at larger cluster-centric radii than the tSZ-galaxy lensing cross-correlation. Combining these measurements with primary CMB data will constrain feedback models through their signatures in the ICM pressure profile. Forces the ability of ongoing and future experiments to constrain such ICM parameters, including the main amplitude of the pressure - mass relation, the redshift evolution of this amplitude, and the mean outer logarithmic slope of the pressure profile. The results are promising, with ~5-20% precision constraints achievable with upcoming experiments, even after marginalizing over cosmological parameters.
1412.3851
Fourier band-power E/B-mode estimators for cosmic shear
Becker, Rozo
New Fourier band-power estimators for cosmic shear analysis and E/B-mode separation. Consider both the case where one performs E/B mode separation and the case where one does not. The resulting estimators have several nice properties which make them idea for comic shear analysis. First, they can be written as linear combinations of the binned cosmic shear correlation functions. Second, they account for the survey window function in real space. Third, they are unbiased by shape noise since they do not use correlation function data at zero separation. Fourth, the band-power functions in Fourier space are compact and largely non-oscillatory. Fifth, they can be used to construct band-power estimators with very efficient data compression properties. In particular, find that all of the information on the parameters Omega_m, sigma8 and n_s in the shear correlation functions in the range of 10'-400' for single tomographic bin can be compressed into only 3 band-power estimates. Lastly, can achieve these rates of data compression while excluding small-scale information where the modeling of the shear correlation functions and power spectra is very difficult. Given these desirable properties, these estimators will be very useful for cosmic shear data analysis.
1412.3854
Designing an inflation galaxy survey: how to measure $\sigma(f_{\rm NL}) \sim 1$ using scale-dependent galaxy bias
de Putter, Doré
BAO surveys require spectroscopic redshifts; to optimize the f_NL^loc measurement, a deep, wide, multi-band imaging survey is preferred. For sigma(f_NL^loc)~1, need i-band AB magnitude depth of i~23, number density ~8/arcmin^2, and a modest photo-z accuracy sigma(z)/(1+z)<0.1, and the ability to measure stellar mass with a precaution ~0.2 dex or better (or another proxy for halo mass with equivalent scatter). Even stronger constraints can potentially be obtained with the galaxy bispectrum.
1412.3862
Why do galaxies stop forming stars? I. The passive fraction - black hole mass relation for central galaxies
Bluck, et al
400k SDSS galaxies at z<0.2: find a strong dependence of the passive fraction on BH mass, which is largely unaffected by the details of the BH mass estimate. Moreover, the passive fraction relationship with BH mass remains strong and tight even at fixed values of galaxy mass M*, DM halo mass Mhalo, and bulge-to-total stellar mass ratio (B/T). The passive fraction dependence on M*, Mhalo and B/T is weak at fixed MBH. These observations show that, for central galaxies, MBH is the strongest correlation with the passive fraction, consistent with quenching from AGN feedback.
1412.3866
Two-size approximation: a simple way of treating the evolution of grain is distribution in galaxies
Hirashita
Propose a simple model of dust enrichment in a galaxy with a simplified treatment of grain size distribution by imposing a `two-size approximation'; that is, all the grain population is represented by small (grain radius a<0.03 um) and large (a>0.03um) grains. Include in the model dust supply from stellar ejecta, destruction in supernova shocks, dust growth by accretion, grain growth by coagulation and grain disruption by shattering, considering how these processes work on the small and large grains. Show that this simple framework reproduces the main features found in full calculations of grain size distributions as follows. The dust enrichment starts with the supply of large grains from stars. At a metallicity level referred to as the critical metallicity of accretion, the abundance of the small grains formed by shattering becomes large enough to rapidly increase the grain abundance by accretion. Associated with the epoch, the mass ratio of the small grains to the large grains reaches the maximum. After that, this ratio converges to the value determined by the balance between shattering and coagulation, and the dust-to-metal ratio is determined by the balance between accretion and shock destruction. With a MC sim, demonstrate that the simplicity of the model has an advantage in predicting statistical properties. Also show some applications for predicting observational dust properties such as extinction curves.
1412.4009
Cross-correlation of near and far-infrared background anisotropies as traced by Spitzer and Herschel
Thacker, et al
Hershel (FIR): 250, 350, 500um; Spitzer: 3.6 um. The cross-correlation between them are detected such that the correlation coefficient at 10' angular scales decreases from 0.3 to 0.1 when the FIR wavelength increases from 250 to 500 um. Model the cross-correlation using a halo model with 3 components: (a) FIR bright or dusty SF galaxies below the masking depth in Herschel maps, (b) NIR faint galaxies below the masking depth at 3.6 um, and (c) intra-halo light, or diffuse stars in DM haloes, that likely dominates fluctuations at 3.5 um. The model is able to reasonably reproduce the autocorrelations at each of the FIR wavelengths and 3.6 um and their corresponding cross-correlations. While the FIR and NIR auto-correlations are dominated by faint dusty, SF galaxies and intra-halo light, respectively, find that roughly half of the cross correlation between NIR and FIR backgrounds is due to the same galaxies that remain unmasked at 3.6 um. The remaining signal in the cross-correlation is due to intra-halo light present in the same DM haloes as those hosting the same faint and unmasked galaxies. In this model, the decrease in the cross-correlation signal from 250um to 500 um comes from the fact that the galaxies that are primarily contributing to 500 um fluctuations peak at a higher redshift than those at 250 um.
1412.4121
Deciphering the 3D structure of the old galactic bulge from the OGLE RR Lyrae stars
Pietrukowicz, et al
Analyzed a sample of 27k fundamental-mode RR Lyrae variable stars (type RRab) detected toward the Galactic bulge by the OGLE survey. The data support that these metal-poor stars trace closely the barred structure formed of intermediate-age red clump giants. The distance to the Galactic center (GC) inferred from the bulge RR Lyrae stars is R_0=8.27pm0.01(stat)pm0.40(sys) kpc. Show that their spatial distribution has the shape of a triaxial ellipsoid with the major axis located in the Galactic plane and inclined at an angle i=20pm3 deg to the Sun-GC line of sight. The obtained scale-length ratio of the major axis to the minor axis in the Galactic plane, and to the axis vertical to the plane is 1:0.49:0.39. We do not see the evidence for the bulge RR Lyrae stars forming an X-shaped structure. Based on the light curve parameters, derive metallicities of the RRab variables and show that there is a very mild but statistically significant radial metallicity gradient. About 60% of the bulge RRab stars form 2 very close sequences on the period-amplitude (or Bailey) diagram, which is interpreted as two major old bulge populations: A and B. Their metallicities likely differ. Population A is about 4 times less abundant than the slightly more metal-poor population B. Most of the remaining stars seem to represent other, even more metal-poor populations of the bulge. The presence of multiple old populations indicates that the MW bulge was initially formed through mergers.
1412.4454
Probing gravity at large scales through CMB lensing
Pullen, Alam, Ho
Describe a methodology to probe gravity with the CMB lensing convergence kappa, specifically by measuring E_G, the ratio of the Laplacian of the gravitational scalar potential difference with the peculiar velocity divergence. Using kappa from CMB lensing as opposed to gg lensing avoids IA while also lacking a hard limit on the lens redshift or significant uncertainties in the source plane. Model E_G for general relativity and modified gravity, finding that E_G for f(R) gravity should be scale-dependent due to the scale-dependence of the growth rate f. Next, construct an estimator for E_G in terms of the lensing convergence-galaxy and galaxy angular power spectra, along with the RSD parameter beta. Also forecast statistical errors of E_G from the current Planck CMB lensing map and the CMASS and LOWZ spectroscopic galaxy samples measured from the BOSS survey, as well as BOSS spectroscopic quasars, from SDSS DR11. Expect this experimental configuration to detect E_G at the level of 11 sigma with CMASS/LOWZ galaxies alone and 13 sigma when BOSS quasars are included. Also find that both upcoming spectroscopic and photometric surveys, each set combined with the final Planck lensing map, can measure precisely both the redshift- and scale-dependence of E_G out to z=2 and higher, with photometric surveys having an advantage due to their large survey areas and high number densities. Finally, advanced ACTPol CMB lensing cross-correlated with spectroscopic (photometric) surveys can differentiate between GR and modified gravity at the level of 3 sigma (13 sigma). Performing a <1% measurement of E_G requires precision in beta on the order of 10%, which is currently achievable with a spectroscopic survey but will be difficult with only a photometric survey.
1412.4606
Intrinsic size correlations in weak lensing
Ciarlariello, Crittenden, Pace
Present a simple model for describing intrinsic correlations for galaxy sizes based on the halo model. Studying these correlations is important both to improve the understanding of galaxy properties and because it is an important potential systematic for WL magnification measurements. The model assumes that the density field drives these intrinsic correlations; also model the distribution of satellite galaxies. Calculate the possible contamination to measurements of lensing convergence PS from galaxy sizes, and show that the cross-correlation of intrinsic sizes with convergence is potentially an important systematic. Also explore how these intrinsic size correlations may affect surveys with different z depth. Find that, in this simple approach, intrinsic size correlations cannot be neglected in order to estimate lensing convergence PS for constraining cosmo parameters.
1412.4727
Optimizing BAO measurements with non-linear transformations of Lyman-alpha forest
Wang, Font-Ribera, Seljak
Explore the effect of applying a NL transformation to the Lyman-a forest transmitted flux F=exp(-tau) and the ability of analytic models to predict the resulting clustering amplitude. Both the large-scale bias of the transformed field (signal) and the amplitude of small scale fluctuations (noise) can be arbitrarily modified, but were unable to find a transformation that increases significantly the S/N ratio on large scales using Taylor expansion to 3rd order. Achieve a 33% improvement in S/N for Gaussianized field in traverse direction. On the other hand, explore analytic model for the large-scale biasing of the Lya forest, and present an extension of this model to describe the biasing of the transformed fields. Using hydrodynamic simulations, show that the model works best to describe the biasing wrt velocity gradients, but is less successful in prediction the biasing wrt large-scale density fluctuations, especially for very NL transformations.
1412.4760
A measurement of the cosmic microwave background gravitational lensing potential from 100 square degrees of SPTpol data
Story, et al
100 sq deg coverage, arc minute resolution at 150 GHz. Using a quadratic estimator, make maps of the CMB lensing potential from combinations of CMB temperature and polarization maps. Combine these lensing potential maps to form a minimum-variance (MV) map. The lensing potential is measured with a S/N ratio of greater than one for angular multipoles between 100<L<250. This is the highest S/N mass map made from CMB to date and will be powerful in cross-correlation with other tracers of large-scale structure. Calculate the PS of the lensing potential for each estimator, and report the value of the MV PS between 100<L<2000 as the primary result. Constrain the ratio of the spectrum to a fiducial LCDM model to be A_MV=0.92. Restricting to polarized data only, find A_POL=0.93. This measurement rejects the hypothesis of no lensing at 5.8 sigma using polarization data alone, and at 14 sigma using both temperature and polarization data.
1412.4781
Measuring primordial non-Gaussianity in the galaxy power spectrum: general relativity makes a difference
Camera, Santos, Maartens
In order to reduce the errors on f_NL, need to include measurements on the largest possible scales. Failure to include the relativistic effects on these scales can introduce significant bias in the best-fit value of f_NL.
1412.4867
Searching for extraterrestrial intelligence with the square kilometer array
Siemion et al
SKA could permit the most sensitive and exhaustive search for technologically-produced radio emission from advanced extraterrestrial intelligence (SETI) ever performed. For example, SKA1-MID will be capable of detecting a source roughly analogous to terrestrial high-power radars (e.g. air rout surveillance or ballistic missile warning radars, EIRP (=equivalent isotropic radiated power, ~1e17 erc/sec) at 10 pc in less than 15 minutes, and with a modest 4 beam SETI observing system could, in one minute, search every star in the primary beam out to ~100 pc for radio emission comparable to that emitted by the Aracibo Planetary Radar (EIRP~2e20 erg/sec). The flexibility of the signal detection systems used for SETI searches with the SKA will allow new algorithms to be employed that will provide sensitivity to a much wider variety of signal types than previously searched for. Discuss the astrobiological and astrophysical motivations for radio SETI and describe how the technical capabilities of the SKA will explore the radio SETI parameter space. Detail several conceivable SETI experimental programs on all components of SKA1, including commensal, primary-user, targeted and survey programs and project the enhancements to them possible with SKA2. Also discuss target selection criteria for these programs, and in the case of commensal observing, how the varied use cases of other primary observers can be used to full advantage for SETI.
1412.4914
Errors on errors - estimating cosmological parameter covariance
Joachimi, Taylor
Current and forthcoming cosmological data analyses share the challenge of huge datasets alongside increasingly tight requirements on the precision and accuracy of extracted cosmological parameters. The community is becoming increasingly aware that these requirements not only apply to the central values of parameters but, equally important, also to the error bars. Due to NL effects in the astrophysics, the instrument, and the analysis pipeline, data covariance matrices are usually not well known a priori and need to be estimated from the data itself, or from suites of large simulations. In either case, the finite number of realizations available to determine data covariances introduces significant biases and additional variance in the errors on cosmological parameters in a standard likelihood analysis. Review recent work on quantifying these biases and additional variances and discuss approaches to remedy these effects.
1412.5172
Neglecting primordial non-Gaussianity threatens future cosmological experiment accuracy
Camera et al
As the title says [abstract gives no more details].
1412.5186
Mesh-free free-form lensing I: methodology and application to mass reconstruction
Merten
Many applications and algorithms in the field of gravitational lensing make use of meshes with a finite number of nodes to analyze and manipulate data. Specific examples in lensing are astronomical CCD images in general, the reconstruction of density distributions from lensing data, lens-source plane mapping or the characterization and interpolation of a PSF. Present a numerical framework to interpolate and differentiate in the mesh-free domain, defined by nodes with coordinates that follow no regular pattern. The framework is based on radial basis functions (RBFs) to smoothly represent data around the nodes. Demonstrate the performance of Gaussian RBF-based, mesh-free interpolation and differentiation, which reaches the sub-percent level in both cases. Use the newly developed framework to translate ideas of non-parametric mass reconstruction from lensing onto the mesh-free domain. The method uses WL and SL constraints and ideally follows the distribution of input data. By reconstruction a simulated mock lens, find that strong-lensing only reconstructions achieve <10% accuracy in the areas where these constraints are available but provide poorer results when departing from these regions. WL only reconstructions give <10% accuracy outside the SL regime, but cannot resolve the inner core structure of the lens. Once both regimes are combined, accurate reconstructions can be achieved over the full field of view and with a spatial resolution which is optimally adapted to the input data.
1412.5584
The stellar mass - halo mass relation from galaxy clustering in VUDS: a high star formation efficiency at z~3
Durkalec, Le Févre, et al
The relation between the galaxy stellar mass M* and the DM halo mass M_h gives important information on the efficiency in forming stars and assembling stellar mass in galaxies. Present the stellar mass to halo mass ratio (SMHR) measurements at 2<z<5, obtained from the VIMOS Ultra Deep Survey. Use HOD modeling of clustering measurements on ~3000 galaxies with spectroscopic redshifts to derive the DM halo mass M_h, and SED fitting over a large set of multi-wavelength data to derive the stellar mass M* and compute the SMHR=M*/M_h. Find that the SMHR ranges from 1% to 2.5% for galaxies with M*=1.3e9 Msun to M*=7.4e9 Msun in DM haloes with M_h=1.3e11 Msun to M_h=3e11 Msun. Derive the integrated SF efficiency (ISFE) of these galaxies and find that the SF efficiency is a moderate 6-9% for lower mass galaxies while it is relatively high at 16% for galaxies with median stellar mass of the sample 7e9 Msun. The lower ISFE at lower masses may indicate that some efficient means of suppressing SF is at work (e.g., SNe feedback), while the high ISFE for the average galaxy at z~3 is indicating that these galaxies are efficiently building -up their stellar mass at a key epoch in the mass assembly process. Further infer that the average mass galaxy at z~3 will start experiencing SF quenching within a few hundred million years.
1412,5593
Deconstructing thermal Sunyaev-Zel'dovich - gravitational lensing cross-correlations: implications for the intracluster medium
Battaglia, Hill, Murray
Using hydro sims, show that these cross-correlation signals are dominated by contributions from hot gas in the ICM, rather than diffuse, unbound gas located beyond the viral radius (the "missing baryons"). Thus, these cross-correlations offer a tool with which to study the ICM over a wide range of halo masses and redshifts. In particular, show that the tSZ-CMB lensing cross-correlation is more sensitive to gas in lower-mass, higher-redshift halos and gas at larger cluster-centric radii than the tSZ-galaxy lensing cross-correlation. Combining these measurements with primary CMB data will constrain feedback models through their signatures in the ICM pressure profile. Forces the ability of ongoing and future experiments to constrain such ICM parameters, including the main amplitude of the pressure - mass relation, the redshift evolution of this amplitude, and the mean outer logarithmic slope of the pressure profile. The results are promising, with ~5-20% precision constraints achievable with upcoming experiments, even after marginalizing over cosmological parameters.
Saturday, December 13, 2014
Day 804
Thursday. Friday. On Saturday.
1412.3110
Vast planes of satellites in a high resolution simulation of the Local Group: comparison to Andromeda
GIllet, et al
Search for vast planes of satellites (VPoS) in a high res sim of the LG, which improves significantly the resolution of former similar studies. Use a simple method for detecting planar configurations of satellites, and validate it on the known plane of M31. Implement a range of prescriptions for modeling the satellite populations, roughly reproducing the variety of recipes used in the literature, and investigate the occurrence and properties of planar structures in these populations. The structure of the simulated satellite systems is strongly non-random and contains planes of satellites, predominantly co-rotating, with, in some cases, sizes comparable to the plane observed in M31. However, the latter is slightly richer in satellites, slightly thinner and has stronger co-rotation, which makes it stand out as overall more exceptional than the simulated planes, when compared to a random population. Although the simulated planes that are found are generally dominated by one real structure, forming its backbone, they are also partly fortuitous and are thus not kinematically coherent structures as a whole. Provided that the simulated and observed planes of satellites are indeed of the same nature, the results suggest that the VPoS of M31 is not a coherent disc and that one third to 1/2 of its satellites must have larger proper motions perpendicular to the plane.
1412.3171
Intergalactic magnetic field spectra from diffuse gamma rays
Chen, et al
Non-vanishing parity-odd correlators of gamma ray arrival directions observed by Fermi-LAT indicate the existence of a helical intergalactic B-field. Successfully test this hypothesis using more stringent cuts of the data, Monte Carlo simulations with Fermi-LAT time exposure information, separate analyses for the northern and southern galactic hemispheres, and confirm predictions made in Tashiro&Vachaspati (2014). With some further technical assumptions, show how to reconstruct the magnetic helicity spectrum from the parity-odd correlations.
1412.3304
Sample of distant rich galaxy clusters in the ROSAT all sky survey
Buddendiek, Schrabback, ... et al
Finding a sample of the most massive clusters with z>0.6 can provide an interesting consistency check of the LCDM model. Present results from the search for clusters with 0.6<z<1.0 where the initial candidates were selected by cross-correlating the RASS faint and bright source catalogs with red galaxies from SDSS DR8. Survey thus covers 10k sq deg, much larger than previous studies. Deeper follow-up observations in 3 bands using the William Herschel Telescope and the LBT were performed to confirm the candidates, resulting in a sample of 44 clusters for which richness and red sequence redshifts are presented, as well as spectroscopic z for a subset. At least two of the cluster in the sample are comparable in richness to RCS2-J232727.7-020437, one of the richest systems discovered to date. Also obtained new observations with CARMA for a subsample of 21 clusters. For 11 of those, detect the SZ signature. The SZ signal allows to estimate M200 and check for tension with the cosmological standard model. Find no tension between cluster masses and the LCDM model.
1412.3451
galpy: a python library for galactic dynamics
Bovy
Describe the design, implementation, and usage of galpy a Python package for galactic-dynamics calculations. At its core, galpy consists of a general framework for representing galactic potentials both in Python an in C (for accelerated computations); galpy functions, objects, and methods can generally take arbitrary combinations of these as arguments. Numerical orbit integration is supported with a variety of Runge-Kutta-type and symplectic integrators. For planar orbits, integration on the phase-space volume is also possible. galpy supports the calculation of action-angle coordinates and orbital frequencies for a given phase-space point for general spherical potentials, using state-of-the-art numerical approximations for axisymmetric potentials, and making use of a recent general approximation for any static potential. A number of different distribution functions (DFs) are also included in the current release; currently these consist of 2d axisymmetric and non-axisymmetric disk DFs, a 3d disk DF, and a DF framework for tidal streams. Provide several examples to illustrate the use of the code. Present a simple model for the MW's gravitational potential consistent with the latest observations. Also numerically calculate the Oort functions for different tracer populations of stars and compare it to a new analytical approximation. Additionally, characterize the response of a kinematically-warm disk to an elliptical m=2 perturbation in detail. Overall, galpy consists of about 54k lines, including 23k lines of code in the model, 11k lines of test code, and about 20k lines of documentation. The test suite covers 99.6% of the code. galpy is available at github.com/jobovy/galpy with extensive documentation at galpy.readthedocs.org.
1412.3464
Lensing time delays as a substructure constraint: a case study with the cluster SDSS~J1004+4112
Mohammed, Saha, Liesenborgs
Gravitational lensing time delays are well known to depend on cosmo params, but they also depend on the details of the mass distribution of the lens. It is usual to model the mass distribution and use time-delay observations to infer cosmological parameters, but it is naturally also possible to take the cosmological parameters as given and use time delays as constraints on the mass distribution. This paper develops a method to isolate what exactly those constraints are, using a principal-components analysis of ensembles of free-form mass models. Find that time delays provide tighter constraints on the distribution of matter in the very high dense regions of the lensing clusters. Apply it to the cluster lens SDSS J1004+4112, whose rich lensing data includes two time delays. Find, assuming a concordance cosmology, that the time delays constrain the central region of the cluster to be rounder and less lopsided than would be allowed by lensed images alone. This detailed information about the distribution of the matter is very useful for studying the dense regions of the galaxy cluster which are very difficult to study with direct measurements. A further time-delay measurement, which is expected, will make this system more interesting.
1412.3683
Cosmological constraints from weak lensing peak statistics with CFHT Stripe-82 survey
Liu, ... Kneib, Leauthaud, Van Waerbeke, ... et al
Derive constraints on cosmo params using WL peak statistics measured on the ~130 sq deg of DS82. This analysis, based on a fast GPU code, demonstrates the feasibility of using peak statistics in cosmo studies. For the measurements, consider peak with S/N ratio in the range [3,6]. For a flat LCDM model with only Omega_m,sigma_8 as free parameters, constrained the parameters of the following relation sigma_8(Omega_m/0.27)^alpha = 0.82 pm 0.03 and alpha=0.43pm0.02. The alpha value found is considerably smaller than the one measured in 2pt and 3pt cosmic shear correlation analyses, showing a significant complementarity of peak statistics to standard WL cosmo studies. The derived constraints on Omega_m,sigma_8 are fully consistent with the ones form either WMAP9 or Planck. From the WL peak abundances alone, obtain marginalized mean values of Omega_m=0.38pm0.25 and sigma_8=0.81pm0.26. Finally, also explored the potential of using WL peak statistics to constrain the mass-concentration relation of DM haloes simultaneously with cosmo parameters.
1412.3703
Constraining the growth of perturbations with lensing of supernovae
Amendola, et al
A recently proposed technique allows one to constrain both the BG and perturbation cosmo params through the distribution function of supernova Ia apparent magnitudes. Extend this technique to alternative cosmo scenarios, in which the growth of structure does not follow the LCDM prescription. Apply the method first to the SN data provided with the JLA catalog combined with z distortion data and with low-z cluster data and show that although the SN alone are not very constraining, they help in reducing the confidence regions. Then apply method to future data from LSST and from a survey that approximates the Euclid satellite mission. In this case, show that the combined data are nicely complementary and can constrain the normalization sigma_8 and the growth rate index game to within 0.5% and 7%, respectively. In particular, the LSST SN catalog is forecast to give the constraint gamma(sigma_8/0.83)^6.7=0.55pm0.1. Also report on constraints relative to a step-wise parameterization of the growth rate of structures. These results show that SN lensing serves as a good cross-check on the measurement of perturbation parameters from more standard techniques.
1412.3110
Vast planes of satellites in a high resolution simulation of the Local Group: comparison to Andromeda
GIllet, et al
Search for vast planes of satellites (VPoS) in a high res sim of the LG, which improves significantly the resolution of former similar studies. Use a simple method for detecting planar configurations of satellites, and validate it on the known plane of M31. Implement a range of prescriptions for modeling the satellite populations, roughly reproducing the variety of recipes used in the literature, and investigate the occurrence and properties of planar structures in these populations. The structure of the simulated satellite systems is strongly non-random and contains planes of satellites, predominantly co-rotating, with, in some cases, sizes comparable to the plane observed in M31. However, the latter is slightly richer in satellites, slightly thinner and has stronger co-rotation, which makes it stand out as overall more exceptional than the simulated planes, when compared to a random population. Although the simulated planes that are found are generally dominated by one real structure, forming its backbone, they are also partly fortuitous and are thus not kinematically coherent structures as a whole. Provided that the simulated and observed planes of satellites are indeed of the same nature, the results suggest that the VPoS of M31 is not a coherent disc and that one third to 1/2 of its satellites must have larger proper motions perpendicular to the plane.
1412.3171
Intergalactic magnetic field spectra from diffuse gamma rays
Chen, et al
Non-vanishing parity-odd correlators of gamma ray arrival directions observed by Fermi-LAT indicate the existence of a helical intergalactic B-field. Successfully test this hypothesis using more stringent cuts of the data, Monte Carlo simulations with Fermi-LAT time exposure information, separate analyses for the northern and southern galactic hemispheres, and confirm predictions made in Tashiro&Vachaspati (2014). With some further technical assumptions, show how to reconstruct the magnetic helicity spectrum from the parity-odd correlations.
1412.3304
Sample of distant rich galaxy clusters in the ROSAT all sky survey
Buddendiek, Schrabback, ... et al
Finding a sample of the most massive clusters with z>0.6 can provide an interesting consistency check of the LCDM model. Present results from the search for clusters with 0.6<z<1.0 where the initial candidates were selected by cross-correlating the RASS faint and bright source catalogs with red galaxies from SDSS DR8. Survey thus covers 10k sq deg, much larger than previous studies. Deeper follow-up observations in 3 bands using the William Herschel Telescope and the LBT were performed to confirm the candidates, resulting in a sample of 44 clusters for which richness and red sequence redshifts are presented, as well as spectroscopic z for a subset. At least two of the cluster in the sample are comparable in richness to RCS2-J232727.7-020437, one of the richest systems discovered to date. Also obtained new observations with CARMA for a subsample of 21 clusters. For 11 of those, detect the SZ signature. The SZ signal allows to estimate M200 and check for tension with the cosmological standard model. Find no tension between cluster masses and the LCDM model.
1412.3451
galpy: a python library for galactic dynamics
Bovy
Describe the design, implementation, and usage of galpy a Python package for galactic-dynamics calculations. At its core, galpy consists of a general framework for representing galactic potentials both in Python an in C (for accelerated computations); galpy functions, objects, and methods can generally take arbitrary combinations of these as arguments. Numerical orbit integration is supported with a variety of Runge-Kutta-type and symplectic integrators. For planar orbits, integration on the phase-space volume is also possible. galpy supports the calculation of action-angle coordinates and orbital frequencies for a given phase-space point for general spherical potentials, using state-of-the-art numerical approximations for axisymmetric potentials, and making use of a recent general approximation for any static potential. A number of different distribution functions (DFs) are also included in the current release; currently these consist of 2d axisymmetric and non-axisymmetric disk DFs, a 3d disk DF, and a DF framework for tidal streams. Provide several examples to illustrate the use of the code. Present a simple model for the MW's gravitational potential consistent with the latest observations. Also numerically calculate the Oort functions for different tracer populations of stars and compare it to a new analytical approximation. Additionally, characterize the response of a kinematically-warm disk to an elliptical m=2 perturbation in detail. Overall, galpy consists of about 54k lines, including 23k lines of code in the model, 11k lines of test code, and about 20k lines of documentation. The test suite covers 99.6% of the code. galpy is available at github.com/jobovy/galpy with extensive documentation at galpy.readthedocs.org.
1412.3464
Lensing time delays as a substructure constraint: a case study with the cluster SDSS~J1004+4112
Mohammed, Saha, Liesenborgs
Gravitational lensing time delays are well known to depend on cosmo params, but they also depend on the details of the mass distribution of the lens. It is usual to model the mass distribution and use time-delay observations to infer cosmological parameters, but it is naturally also possible to take the cosmological parameters as given and use time delays as constraints on the mass distribution. This paper develops a method to isolate what exactly those constraints are, using a principal-components analysis of ensembles of free-form mass models. Find that time delays provide tighter constraints on the distribution of matter in the very high dense regions of the lensing clusters. Apply it to the cluster lens SDSS J1004+4112, whose rich lensing data includes two time delays. Find, assuming a concordance cosmology, that the time delays constrain the central region of the cluster to be rounder and less lopsided than would be allowed by lensed images alone. This detailed information about the distribution of the matter is very useful for studying the dense regions of the galaxy cluster which are very difficult to study with direct measurements. A further time-delay measurement, which is expected, will make this system more interesting.
1412.3683
Cosmological constraints from weak lensing peak statistics with CFHT Stripe-82 survey
Liu, ... Kneib, Leauthaud, Van Waerbeke, ... et al
Derive constraints on cosmo params using WL peak statistics measured on the ~130 sq deg of DS82. This analysis, based on a fast GPU code, demonstrates the feasibility of using peak statistics in cosmo studies. For the measurements, consider peak with S/N ratio in the range [3,6]. For a flat LCDM model with only Omega_m,sigma_8 as free parameters, constrained the parameters of the following relation sigma_8(Omega_m/0.27)^alpha = 0.82 pm 0.03 and alpha=0.43pm0.02. The alpha value found is considerably smaller than the one measured in 2pt and 3pt cosmic shear correlation analyses, showing a significant complementarity of peak statistics to standard WL cosmo studies. The derived constraints on Omega_m,sigma_8 are fully consistent with the ones form either WMAP9 or Planck. From the WL peak abundances alone, obtain marginalized mean values of Omega_m=0.38pm0.25 and sigma_8=0.81pm0.26. Finally, also explored the potential of using WL peak statistics to constrain the mass-concentration relation of DM haloes simultaneously with cosmo parameters.
1412.3703
Constraining the growth of perturbations with lensing of supernovae
Amendola, et al
A recently proposed technique allows one to constrain both the BG and perturbation cosmo params through the distribution function of supernova Ia apparent magnitudes. Extend this technique to alternative cosmo scenarios, in which the growth of structure does not follow the LCDM prescription. Apply the method first to the SN data provided with the JLA catalog combined with z distortion data and with low-z cluster data and show that although the SN alone are not very constraining, they help in reducing the confidence regions. Then apply method to future data from LSST and from a survey that approximates the Euclid satellite mission. In this case, show that the combined data are nicely complementary and can constrain the normalization sigma_8 and the growth rate index game to within 0.5% and 7%, respectively. In particular, the LSST SN catalog is forecast to give the constraint gamma(sigma_8/0.83)^6.7=0.55pm0.1. Also report on constraints relative to a step-wise parameterization of the growth rate of structures. These results show that SN lensing serves as a good cross-check on the measurement of perturbation parameters from more standard techniques.
Thursday, December 11, 2014
Day 803
Wednesday.
1412.0133
New constraints on $f(R)$ gravity from clusters of galaxies
Cataneo, Rapetti, ... Mantz, Allen, Applegate, ... von der Linden, ... et al
The abundance of massive galaxy clusters is a probe of departures from GR on cosmic scales. Despite current stringent constraints placed by stellar and galactic tests, on large scales alternative theories of gravity such as f(R) can still work as effective theories Here, present constraints on two popular models of f(R), Hu-Sawicki and "designer", derived from a fully self-consistent analysis of current samples of X-ray selected clusters and accounting for al the covariances between cosmological and astrophysical parameters. Constraints are mainly driven by cluster number counts, and we obtain substantial improvements on previous upper bounds employing this method. Also combine these results with recent data from the CMB and the CMB lensing potential generated by LSS, as well as with other cosmological constraints on the background expansion history and its mean matter density. The robustness of the results derives from high quality cluster growth data for the most massive clusters known out to z~0.5, a tight control of systematic uncertainties including an accurate and precise mass calibration from WL, and the use of the full shape of the halo MF over the mass range of data.
1412.2745
Deuterium enrichment of the interstellar medium
Das, Majumdar, Chakrabarti, Sahu
Explore various aspects of D enrichment by constructing a chemical evolution model in gas and grain phases. Depending on various physical parameters, gas and grains are allowed to interact with each other through exchange of their chemical species. It is known that HCO+ and N2H+ are two abundant gas phase ions in ISM and their D fractionation are generally used to predict degree of ionization in various regions of a molecular cloud. To have a more realistic estimation, consider a density profile of a collapsing cloud. Present radial distributions of important interstellar molecules along with their deuterated isotopomer. Carry out quantum chemical simulation to study effects of isotropic substitution on spectral properties of these important interstellar species. Calculate vibrational (harmonic) frequency of the most important deuterated species (neutral & ions). Rotational and distortional constants of these molecules are also computed to predict rotational transitions of these species. Compare vibrational (harmonic) and rotational transitions as computed here with existing observational, experimental and theoretical results. Results would assist observes in their quest of several hitherto unobserved deuterated species.
1412.2748
Local group galaxies emerge from the dark
Sawala, Frenk, ...
The LCDM model of cosmic structure formation is eminently falsifiable: once its parameters are fixed on large scales, it becomes testable in the nearby Universe. Observations within our Local Group of galaxies, including the satellite populations of the MW and Andromeda, appear to contradict LCDM predictions: there are far fewer satellite galaxies than DM haloes (the "missing satellites" problem), galaxies seem to avoid the largest substructures (the "too big to fail" problem), and the brightest satellites appear to orbit their host galaxies on a thin plane (the "planes of satellites" problem). Present results from the first hydrodynamic simulations of the LG that match the observed abundance of galaxies. Find that when baryonic and DM are followed simultaneously in the context of a realistic galaxy formation model, all 3 "problems" are resolved within the LCDM paradigm.
1412.0133
New constraints on $f(R)$ gravity from clusters of galaxies
Cataneo, Rapetti, ... Mantz, Allen, Applegate, ... von der Linden, ... et al
The abundance of massive galaxy clusters is a probe of departures from GR on cosmic scales. Despite current stringent constraints placed by stellar and galactic tests, on large scales alternative theories of gravity such as f(R) can still work as effective theories Here, present constraints on two popular models of f(R), Hu-Sawicki and "designer", derived from a fully self-consistent analysis of current samples of X-ray selected clusters and accounting for al the covariances between cosmological and astrophysical parameters. Constraints are mainly driven by cluster number counts, and we obtain substantial improvements on previous upper bounds employing this method. Also combine these results with recent data from the CMB and the CMB lensing potential generated by LSS, as well as with other cosmological constraints on the background expansion history and its mean matter density. The robustness of the results derives from high quality cluster growth data for the most massive clusters known out to z~0.5, a tight control of systematic uncertainties including an accurate and precise mass calibration from WL, and the use of the full shape of the halo MF over the mass range of data.
1412.2745
Deuterium enrichment of the interstellar medium
Das, Majumdar, Chakrabarti, Sahu
Explore various aspects of D enrichment by constructing a chemical evolution model in gas and grain phases. Depending on various physical parameters, gas and grains are allowed to interact with each other through exchange of their chemical species. It is known that HCO+ and N2H+ are two abundant gas phase ions in ISM and their D fractionation are generally used to predict degree of ionization in various regions of a molecular cloud. To have a more realistic estimation, consider a density profile of a collapsing cloud. Present radial distributions of important interstellar molecules along with their deuterated isotopomer. Carry out quantum chemical simulation to study effects of isotropic substitution on spectral properties of these important interstellar species. Calculate vibrational (harmonic) frequency of the most important deuterated species (neutral & ions). Rotational and distortional constants of these molecules are also computed to predict rotational transitions of these species. Compare vibrational (harmonic) and rotational transitions as computed here with existing observational, experimental and theoretical results. Results would assist observes in their quest of several hitherto unobserved deuterated species.
1412.2748
Local group galaxies emerge from the dark
Sawala, Frenk, ...
The LCDM model of cosmic structure formation is eminently falsifiable: once its parameters are fixed on large scales, it becomes testable in the nearby Universe. Observations within our Local Group of galaxies, including the satellite populations of the MW and Andromeda, appear to contradict LCDM predictions: there are far fewer satellite galaxies than DM haloes (the "missing satellites" problem), galaxies seem to avoid the largest substructures (the "too big to fail" problem), and the brightest satellites appear to orbit their host galaxies on a thin plane (the "planes of satellites" problem). Present results from the first hydrodynamic simulations of the LG that match the observed abundance of galaxies. Find that when baryonic and DM are followed simultaneously in the context of a realistic galaxy formation model, all 3 "problems" are resolved within the LCDM paradigm.
Tuesday, December 9, 2014
Day 802
Tuesday.
1412.2132
The kiloparsec-scale star formation law at redshift 4: wide-spread, highly efficient star formation in the dust-obscured starburst galaxy GN20
Hodge et al
High-resolution 880um (rest-frame FIR) continuum emission in the z=4.05 sub millimeter galaxy GN20 resolve the obscured SF in this unlensed galaxy on scales of 2.1x1.3 kpc (0.3"x0.2"). The observations reveal a bright dusty starburst centered on the cold molecular gas reservoir and showing a bar-like extension along the major axis. The striking anti-correlation with the HST/WFC3 imaging suggests that the copious dust surrounding the starburst heavily obscures the rest-frame UV/optical emission. A comparison with 1.2mm PdBI continuum data reveals no evidence for variations in the dust properties across the source within the uncertainties, consistent with extended SF, and the peak SFR surface density 119pm8 Msun/yr/kpc2 implies that the SF in GN20 remains sub-Eddington on scales down to 3 kpc2. Find that the SF efficiency is highest in the central regions of GN20, leading to a resolved SF law with a power law slope of 2.1, and that GN20 lies above the sequence of normal SF disks, implying that the dispersion in the SF law is not due solely to morphology or choice of conversion factor. These data extend previous evidence for a fixed SF efficiency per free-fall time to include the SF medium on ~kpc-scales in a galaxy 12 Gyr ago.
1412.2137
Evidence for the inside-out growth of the stellar mass distribution in galaxy clusters since z~1
van der Burg, Hoekstra, et al
Study the radial number density and stellar mass density distributions of satellite galaxies in a sample of 60 massive clusters at 0.04<z<0.26 from MENeaCS and CCCP. In addition to ~10k spectroscopically confirmed member galaxies, use deep ugri-band imaging to estimate photometric z and stellar masses, and then statistically subtract fore- and background sources using data from the COSMOS survey. Measure the galaxy number density and stellar mass density distributions in logarithmically spaced bins over 2 orders of magnitude in radial distance from the BCGs. For projected distances in the range 0.1<R/R200<2.0, find that the stellar mass distribution is well-described by an NFW profile with a concentration of c=2.03pm0.20. However, at smaller radii measure a significant excess in the stellar mass in satellite galaxies of about 1e11 Msun per cluster, compared to these NFW profiles. Obtain good fits to generalized NFW profiles with free inner slopes, and to Einasto profiles. To examine how clusters assemble their stellar mass component over cosmic time, compare this local sample to the GCLASS cluster sample at z~1, which represents the approximate progenitor sample of the low-z clusters. This allows for a direct comparison, which suggests that the central parts (R<0.4 Mpc) of the stellar mass distributions of satellites in local galaxy clusters are already in place at z~1, and contain sufficient excess material for further BCG growth. Evolving towards z=0, clusters appear to assemble their stellar mass primary onto the outskirts, making them grow in an inside-out fashion.
1412.2141
Galaxy and mass assembly (GAMA): the galaxy luminosity function within the cosmic web
Eardley, Peacock, et al
Investigate the dependence of the galaxy LF on geometric environment within GAMA. Find a significant variation in the LF of galaxies between different geometric environments; the normalization, characterized by phi* in Schechter function fit, increases by an order of magnitude from voids to knots. The turnover magnitude, characterized by M*, brightens by approximately 0.5 mag from voids to knots. However, show that the observed modulation can be entirely attributed to they direct local-density dependence. Therefore find no evidence of a direct influence of the cosmic web on the galaxy luminosity function.
1412.2208
Combining spectroscopic and photometric surveys using angular cross-correlations I: Algorithm and modeling
Eriksen, Gaztanaga
WL clustering is studied using angular coordinates, while RSD and BAO use 3d coordinates, which requires a model dependent conversion of angles and redshifts into comoving distances. Explore modeling multi-tracer galaxy clustering (of WL, BAO and RSD), using only 2d cross-correlations in thin z bins. This involves evaluating many thousands cross-correlations, each a multidimensional integral, which is computationally demanding. Present a new algorithm that performs these calculations as matrix operations. Nearby narrow redshift bins are intrinsically correlated, which can be used to recover the full (radial) 3d information. Show that the Limber approximation does not work well for this task. In the exact calculation, both the clustering amplitude and the RSD effect increase when decreasing the redshift bin width. For narrow bins, the cross-correlations has a larger BAO peak than the auto-correlation because smaller scales are filtered out by the radial z separation. Moreover, the BAO peak shows a second (ghost) peak, shifted to smaller angle. Explore how WL, RSD and BAO contribute to the cross-correlations as a function of the redshift bin width and present a first exploration of non-linear effects and signal-to-noise ratio on these quantities. This illustrates the new approach to clustering analysis provides new insights and is potentially viable in practice.
1412.2529
Far-infrared excess emission as a tracer of disk-halo interaction
Lenz, Kerp, ... et al
Given the current and past SF in the MW in combination with the limited gas supply, the re-fuelling of the reservoir of cool gas is an important aspect of Galactic astrophysics. The infall of H_i halo clouds can, among other mechanisms, contribute to solving this problem. Study the intermediate-velocity cloud IVC135+54 and its spatially associated high-velocity counterpart to look for signs of a past or ongoing interaction. Using the Effelsberg-Bonn H_i Survey data, investigate the interplay of gas at different velocities. In combination with FIR Planck and IRIS data, extended this study to instestellar dust and used the correlation of the data sets to infer information on the dark gas. The velocity structure indicates a strong compression and deceleration of the infalling HVC, associated with FIR excess emission in the intermediate-velocity cloud. This excess emission traces molecular hydrogen, confirming that IVC135+54 is one of the very few molecular halo clouds. The high dust emissivity of IVC135+54 with respect to the local gas implies that it consists of disk material and does not, unlike the HVC, have an extragalactic origin. Based on the velocity structure of the HVC and the dust content of the IVC, a physical connection between them appears to be the logical conclusion. Since this is not compatible with the distance difference between the two objects, conclude that this particular HVC might be much closer to us than complex C. Alternatively, the indicators for an interaction are misleading and have another origin.
1412.2132
The kiloparsec-scale star formation law at redshift 4: wide-spread, highly efficient star formation in the dust-obscured starburst galaxy GN20
Hodge et al
High-resolution 880um (rest-frame FIR) continuum emission in the z=4.05 sub millimeter galaxy GN20 resolve the obscured SF in this unlensed galaxy on scales of 2.1x1.3 kpc (0.3"x0.2"). The observations reveal a bright dusty starburst centered on the cold molecular gas reservoir and showing a bar-like extension along the major axis. The striking anti-correlation with the HST/WFC3 imaging suggests that the copious dust surrounding the starburst heavily obscures the rest-frame UV/optical emission. A comparison with 1.2mm PdBI continuum data reveals no evidence for variations in the dust properties across the source within the uncertainties, consistent with extended SF, and the peak SFR surface density 119pm8 Msun/yr/kpc2 implies that the SF in GN20 remains sub-Eddington on scales down to 3 kpc2. Find that the SF efficiency is highest in the central regions of GN20, leading to a resolved SF law with a power law slope of 2.1, and that GN20 lies above the sequence of normal SF disks, implying that the dispersion in the SF law is not due solely to morphology or choice of conversion factor. These data extend previous evidence for a fixed SF efficiency per free-fall time to include the SF medium on ~kpc-scales in a galaxy 12 Gyr ago.
1412.2137
Evidence for the inside-out growth of the stellar mass distribution in galaxy clusters since z~1
van der Burg, Hoekstra, et al
Study the radial number density and stellar mass density distributions of satellite galaxies in a sample of 60 massive clusters at 0.04<z<0.26 from MENeaCS and CCCP. In addition to ~10k spectroscopically confirmed member galaxies, use deep ugri-band imaging to estimate photometric z and stellar masses, and then statistically subtract fore- and background sources using data from the COSMOS survey. Measure the galaxy number density and stellar mass density distributions in logarithmically spaced bins over 2 orders of magnitude in radial distance from the BCGs. For projected distances in the range 0.1<R/R200<2.0, find that the stellar mass distribution is well-described by an NFW profile with a concentration of c=2.03pm0.20. However, at smaller radii measure a significant excess in the stellar mass in satellite galaxies of about 1e11 Msun per cluster, compared to these NFW profiles. Obtain good fits to generalized NFW profiles with free inner slopes, and to Einasto profiles. To examine how clusters assemble their stellar mass component over cosmic time, compare this local sample to the GCLASS cluster sample at z~1, which represents the approximate progenitor sample of the low-z clusters. This allows for a direct comparison, which suggests that the central parts (R<0.4 Mpc) of the stellar mass distributions of satellites in local galaxy clusters are already in place at z~1, and contain sufficient excess material for further BCG growth. Evolving towards z=0, clusters appear to assemble their stellar mass primary onto the outskirts, making them grow in an inside-out fashion.
1412.2141
Galaxy and mass assembly (GAMA): the galaxy luminosity function within the cosmic web
Eardley, Peacock, et al
Investigate the dependence of the galaxy LF on geometric environment within GAMA. Find a significant variation in the LF of galaxies between different geometric environments; the normalization, characterized by phi* in Schechter function fit, increases by an order of magnitude from voids to knots. The turnover magnitude, characterized by M*, brightens by approximately 0.5 mag from voids to knots. However, show that the observed modulation can be entirely attributed to they direct local-density dependence. Therefore find no evidence of a direct influence of the cosmic web on the galaxy luminosity function.
1412.2208
Combining spectroscopic and photometric surveys using angular cross-correlations I: Algorithm and modeling
Eriksen, Gaztanaga
WL clustering is studied using angular coordinates, while RSD and BAO use 3d coordinates, which requires a model dependent conversion of angles and redshifts into comoving distances. Explore modeling multi-tracer galaxy clustering (of WL, BAO and RSD), using only 2d cross-correlations in thin z bins. This involves evaluating many thousands cross-correlations, each a multidimensional integral, which is computationally demanding. Present a new algorithm that performs these calculations as matrix operations. Nearby narrow redshift bins are intrinsically correlated, which can be used to recover the full (radial) 3d information. Show that the Limber approximation does not work well for this task. In the exact calculation, both the clustering amplitude and the RSD effect increase when decreasing the redshift bin width. For narrow bins, the cross-correlations has a larger BAO peak than the auto-correlation because smaller scales are filtered out by the radial z separation. Moreover, the BAO peak shows a second (ghost) peak, shifted to smaller angle. Explore how WL, RSD and BAO contribute to the cross-correlations as a function of the redshift bin width and present a first exploration of non-linear effects and signal-to-noise ratio on these quantities. This illustrates the new approach to clustering analysis provides new insights and is potentially viable in practice.
1412.2529
Far-infrared excess emission as a tracer of disk-halo interaction
Lenz, Kerp, ... et al
Given the current and past SF in the MW in combination with the limited gas supply, the re-fuelling of the reservoir of cool gas is an important aspect of Galactic astrophysics. The infall of H_i halo clouds can, among other mechanisms, contribute to solving this problem. Study the intermediate-velocity cloud IVC135+54 and its spatially associated high-velocity counterpart to look for signs of a past or ongoing interaction. Using the Effelsberg-Bonn H_i Survey data, investigate the interplay of gas at different velocities. In combination with FIR Planck and IRIS data, extended this study to instestellar dust and used the correlation of the data sets to infer information on the dark gas. The velocity structure indicates a strong compression and deceleration of the infalling HVC, associated with FIR excess emission in the intermediate-velocity cloud. This excess emission traces molecular hydrogen, confirming that IVC135+54 is one of the very few molecular halo clouds. The high dust emissivity of IVC135+54 with respect to the local gas implies that it consists of disk material and does not, unlike the HVC, have an extragalactic origin. Based on the velocity structure of the HVC and the dust content of the IVC, a physical connection between them appears to be the logical conclusion. Since this is not compatible with the distance difference between the two objects, conclude that this particular HVC might be much closer to us than complex C. Alternatively, the indicators for an interaction are misleading and have another origin.
Monday, December 8, 2014
Day 801
Monday.
1412.1825
GREAT3 results I: systematic errors in shear estimation and the impact of real galaxy morphology
Mandelbaum, Rowe, et al
First results from GREAT3, which was divided into experiments to test 3 specific questions, and included simulated space- and ground-based data with constant or cosmologically-varying shear fields. The simplest (control) experiment included parametric galaxies with a realistic distribution of S/N, size and ellipticity, and a complex PSF. The other experiments tested the additional impact of realistic galaxy morphology, multiple exposure imaging, and the uncertainty about a spatially-varying PSF; the last 2 questions will be explored in Paper II. The 24 participating teams competed to estimate lensing shears to within systematic error tolerances for upcoming Stage-IV DE surveys, making 1525 submissions overall. GREAT3 saw considerable variety and innovation in the type of methods applied. Several teams now meet or exceed the targets in many of the tests conducted (to within the statistical errors). Conclude that the presence of realistic galaxy morphology in simulations changes shear calibration biases by ~1% for a wide range of methods. Other effects such as truncation biases due to finite galaxy postage stamps, and the impact of galaxy type as measured by the Sersic index, are quantified for the first time. Results generalize previous studies regarding sensitivities to galaxy size and S/N, and to PSF properties such as seeing and defocus. Almost all methods' results support the simple model in which additive shear biases depend linearly on PSF ellipticity.
1412.1835
The MOSFIRE Deep Evolution Field (MOSDEF) survey: rest-frame optical spectroscopy for ~1500 H-selected galaxies at 1.37 < z < 3.8
Kriek, Shapley, ... Coil, et al
MOSDEF aims to obtain moderate-resolution (R=3000-3650) rest-frame optical spectra (~3700-7000A) for ~1500 galaxies at 1.37<z<3.80 in three well- studied CANDELS fields: AEGIS, COSMOS and GOODS-N. Targets are selected in 3 z intervals: 1.37<z<1.70, 2.09<z<2.61, and 2.95<z<3.80, down to fixed H_AB( F160W) magnitudes of 24.0, 24.5, and 25.0, respectively, using the photometric and spectroscopic catalogs from the 3D-HST survey. Target both strong nebular emission lines (e.g., [OII], Hbeta, [OIII], 5008, Halpha, [NII] and [SII]) and stellar continuum and absorption features (e.g., Balmer lines, Ca-II H and K, Mob, 4000 A break). Here, present an overview of the survey, the observational strategy, the data reduction and analysis, and the sample characteristics based on spectra obtained during the first 24 nights. To date, completed 21 masks, obtaining spectra of 591 galaxies, which were serendipitously detected. The MOSDEF galaxy sample includes unobscured star-forming, dusty SF, and quiescent galaxies and spans a wide range in stellar mass (1e9-11.5 Msun) and SFR (~0-1e4 Msun/yr). The spectroscopically confirmed sample is roughly representative of an H-band limited galaxy sample at these redshifts. With its large sample size, broad diversity in galaxy properties, and wealth of available ancillary data, MOSDEF will transform understanding of the stellar, gaseous, metal, dust and black hole content of galaxies during the time when the universe was most active.
1412.1839
Dissipative dark mater and the andromeda plane of satellites
Randall, Scholtz
Show that dissipative DM can potentially explain the large observed M/L ratio of the dwarf satellite galaxies that have been observed in the recently identified planar structure around Andromeda, which are thought to result from tidal forces during a galaxy merger. Whereas dwarf galaxies created from ordinary disks would be dark matter poor, DM inside the galactic plane not only provides a source of DM, but one that is more readily bound due to the DM's lower velocity. This initial N-body study shows that with a thin disk of DM inside the baryonic disk, M/L ratios as high as O(30) can be generated when tidal forces pull out patches of sizes similar to the scales of Toomre instabilities of the dark disk. A full simulation will be needed to confirm this result.
1412.1825
GREAT3 results I: systematic errors in shear estimation and the impact of real galaxy morphology
Mandelbaum, Rowe, et al
First results from GREAT3, which was divided into experiments to test 3 specific questions, and included simulated space- and ground-based data with constant or cosmologically-varying shear fields. The simplest (control) experiment included parametric galaxies with a realistic distribution of S/N, size and ellipticity, and a complex PSF. The other experiments tested the additional impact of realistic galaxy morphology, multiple exposure imaging, and the uncertainty about a spatially-varying PSF; the last 2 questions will be explored in Paper II. The 24 participating teams competed to estimate lensing shears to within systematic error tolerances for upcoming Stage-IV DE surveys, making 1525 submissions overall. GREAT3 saw considerable variety and innovation in the type of methods applied. Several teams now meet or exceed the targets in many of the tests conducted (to within the statistical errors). Conclude that the presence of realistic galaxy morphology in simulations changes shear calibration biases by ~1% for a wide range of methods. Other effects such as truncation biases due to finite galaxy postage stamps, and the impact of galaxy type as measured by the Sersic index, are quantified for the first time. Results generalize previous studies regarding sensitivities to galaxy size and S/N, and to PSF properties such as seeing and defocus. Almost all methods' results support the simple model in which additive shear biases depend linearly on PSF ellipticity.
1412.1835
The MOSFIRE Deep Evolution Field (MOSDEF) survey: rest-frame optical spectroscopy for ~1500 H-selected galaxies at 1.37 < z < 3.8
Kriek, Shapley, ... Coil, et al
MOSDEF aims to obtain moderate-resolution (R=3000-3650) rest-frame optical spectra (~3700-7000A) for ~1500 galaxies at 1.37<z<3.80 in three well- studied CANDELS fields: AEGIS, COSMOS and GOODS-N. Targets are selected in 3 z intervals: 1.37<z<1.70, 2.09<z<2.61, and 2.95<z<3.80, down to fixed H_AB( F160W) magnitudes of 24.0, 24.5, and 25.0, respectively, using the photometric and spectroscopic catalogs from the 3D-HST survey. Target both strong nebular emission lines (e.g., [OII], Hbeta, [OIII], 5008, Halpha, [NII] and [SII]) and stellar continuum and absorption features (e.g., Balmer lines, Ca-II H and K, Mob, 4000 A break). Here, present an overview of the survey, the observational strategy, the data reduction and analysis, and the sample characteristics based on spectra obtained during the first 24 nights. To date, completed 21 masks, obtaining spectra of 591 galaxies, which were serendipitously detected. The MOSDEF galaxy sample includes unobscured star-forming, dusty SF, and quiescent galaxies and spans a wide range in stellar mass (1e9-11.5 Msun) and SFR (~0-1e4 Msun/yr). The spectroscopically confirmed sample is roughly representative of an H-band limited galaxy sample at these redshifts. With its large sample size, broad diversity in galaxy properties, and wealth of available ancillary data, MOSDEF will transform understanding of the stellar, gaseous, metal, dust and black hole content of galaxies during the time when the universe was most active.
1412.1839
Dissipative dark mater and the andromeda plane of satellites
Randall, Scholtz
Show that dissipative DM can potentially explain the large observed M/L ratio of the dwarf satellite galaxies that have been observed in the recently identified planar structure around Andromeda, which are thought to result from tidal forces during a galaxy merger. Whereas dwarf galaxies created from ordinary disks would be dark matter poor, DM inside the galactic plane not only provides a source of DM, but one that is more readily bound due to the DM's lower velocity. This initial N-body study shows that with a thin disk of DM inside the baryonic disk, M/L ratios as high as O(30) can be generated when tidal forces pull out patches of sizes similar to the scales of Toomre instabilities of the dark disk. A full simulation will be needed to confirm this result.
Thursday, December 4, 2014
Day 800
Friday.
1412.1472
New redshift z~9 galaxies in the Hubble Frontier Fields: Implications for early evolution of the UV luminosity density
McLeod et al
Survey covering an effective area of 10.9 sq arcmin (after accounting for magnification) which yields 12 galaxies at 8.4<z<9.5 (based on photo-z). Also uncover 4 z~9 galaxies. Based on published magnification maps, find that only on of the 12 is likely boosted by more than a factor of 2 by gravitational lensing. Consequently, perform a fairly straightforward reanalysis of the normalization of the z~9 UV galaxy LF as expired previously in the HUDF12 program. Conclude that the new data strengthen the evidence for a continued smooth decline in UV luminosity density (and hence SFR density) from z~8 to 9, contrary to recent reports of a marked drop-off at these redshifts. This provide further support for the scenario in which early galaxy evolution is sufficiently extended to explain cosmic reionization.
1412.1482
Overview of the SDSS-IV MaNGA survey: mapping nearby galaxies at Apache Point Observatory
Bundy, et al
Overview of a new integral field spectroscopic survey called MaNGA (Mapping Nearby Galaxies at Apache Point Observatory), one of 3 core programs in SDSS-IV that began 2014 July 1. MaNGA will investigate the internal kinematic structure and composition of gas and stars in an unprecedented sample of 10k nearby galaxies. Summarize essential characteristics of the instrument and survey design in the context of MaNGA's key science goals and present prototype observations to demonstrate MaNGA's scientific potential. MaNGA employs dithered observations with 17 fiber-bundle integral field units that vary in diameter from 12" (19 fibers) to 32" (127 fibers). Two dual-channel spectrographs provide simultaneous wavelength coverage over 3600-10300A at R~2000. With a typical integration time of 3 hr, MaNGA reaches a target r-band S/N of 4-8 (per A, per 2" fiber) at 23 AB mag per sq arcsec, which is typical for the outskirts of MaNGA galaxies. Targets are selected with stellar mass greater than 1e9 Msun using SDSS-I redshifts and i-band luminosity to achieve uniform radial coverage in terms of the effective radius, an approximately flat distribution in stellar mass, and a sample spanning a wide range of environments. Analysis of prototype observations demonstrate MaNGA's ability to probe gas ionization, shed light on recent star formation and quenching, enable dynamical modeling, decompose constitution components, and map the composition of stellar populations. MaNGA's spatially resolved spectra will enable an unprecedented study of the astrophysics of nearby galaxies in the coming 6 years.
1412.1507
Protocluster discovery in tomographic Ly$\alpha$ forest flux maps
Stark, White, Lee, Hennawi
Present a new method of finding protoclusters using tomographic maps of Lya Forest flux. Review method of creating tomographic flux maps and discuss new high performance implementation, which makes large reconstructions computationally feasible. Using a large N-body simulation, illustrate how protoclusters create large-scale flux decrements, roughly 10 Mpc/h across, and how we can use this signal to find them in flux maps. Test the performance of protocluster finding method by running it on the ideal, noiseless map and tomographic reconstructions from mock surveys, and comparing to the halo catalog. Using the noiseless map, find protocluster candidates with about 90% purity, and recover about 75% of the protoclusters that form massive clusters (>3e14 Msun/h). Construct mock surveys similar to the ongoing COSMOS Ly-A mapping And Tomography Observations (CLAMATO) survey While the existing data has an average sightling separation of 2.3 Mpc/h, test separations of 2-6 Mpc/h to see what can be tolerated for the application. Using reconstructed maps from small separation mock surveys, the protocluster candidate purity and completeness are very close to what was found in the noiseless case, As the sightline separation increases, the purity and completeness decrease, although they remain much higher than initially expected. Extend test cases to mock surveys with an average separation of 15 Mpc/h, meant to reproduce high source density areas of the BOSS survey. Find that even with such a large sightline separation, the method can still be used to find some f the largest protoclusters.
1412.1472
New redshift z~9 galaxies in the Hubble Frontier Fields: Implications for early evolution of the UV luminosity density
McLeod et al
Survey covering an effective area of 10.9 sq arcmin (after accounting for magnification) which yields 12 galaxies at 8.4<z<9.5 (based on photo-z). Also uncover 4 z~9 galaxies. Based on published magnification maps, find that only on of the 12 is likely boosted by more than a factor of 2 by gravitational lensing. Consequently, perform a fairly straightforward reanalysis of the normalization of the z~9 UV galaxy LF as expired previously in the HUDF12 program. Conclude that the new data strengthen the evidence for a continued smooth decline in UV luminosity density (and hence SFR density) from z~8 to 9, contrary to recent reports of a marked drop-off at these redshifts. This provide further support for the scenario in which early galaxy evolution is sufficiently extended to explain cosmic reionization.
1412.1482
Overview of the SDSS-IV MaNGA survey: mapping nearby galaxies at Apache Point Observatory
Bundy, et al
Overview of a new integral field spectroscopic survey called MaNGA (Mapping Nearby Galaxies at Apache Point Observatory), one of 3 core programs in SDSS-IV that began 2014 July 1. MaNGA will investigate the internal kinematic structure and composition of gas and stars in an unprecedented sample of 10k nearby galaxies. Summarize essential characteristics of the instrument and survey design in the context of MaNGA's key science goals and present prototype observations to demonstrate MaNGA's scientific potential. MaNGA employs dithered observations with 17 fiber-bundle integral field units that vary in diameter from 12" (19 fibers) to 32" (127 fibers). Two dual-channel spectrographs provide simultaneous wavelength coverage over 3600-10300A at R~2000. With a typical integration time of 3 hr, MaNGA reaches a target r-band S/N of 4-8 (per A, per 2" fiber) at 23 AB mag per sq arcsec, which is typical for the outskirts of MaNGA galaxies. Targets are selected with stellar mass greater than 1e9 Msun using SDSS-I redshifts and i-band luminosity to achieve uniform radial coverage in terms of the effective radius, an approximately flat distribution in stellar mass, and a sample spanning a wide range of environments. Analysis of prototype observations demonstrate MaNGA's ability to probe gas ionization, shed light on recent star formation and quenching, enable dynamical modeling, decompose constitution components, and map the composition of stellar populations. MaNGA's spatially resolved spectra will enable an unprecedented study of the astrophysics of nearby galaxies in the coming 6 years.
1412.1507
Protocluster discovery in tomographic Ly$\alpha$ forest flux maps
Stark, White, Lee, Hennawi
Present a new method of finding protoclusters using tomographic maps of Lya Forest flux. Review method of creating tomographic flux maps and discuss new high performance implementation, which makes large reconstructions computationally feasible. Using a large N-body simulation, illustrate how protoclusters create large-scale flux decrements, roughly 10 Mpc/h across, and how we can use this signal to find them in flux maps. Test the performance of protocluster finding method by running it on the ideal, noiseless map and tomographic reconstructions from mock surveys, and comparing to the halo catalog. Using the noiseless map, find protocluster candidates with about 90% purity, and recover about 75% of the protoclusters that form massive clusters (>3e14 Msun/h). Construct mock surveys similar to the ongoing COSMOS Ly-A mapping And Tomography Observations (CLAMATO) survey While the existing data has an average sightling separation of 2.3 Mpc/h, test separations of 2-6 Mpc/h to see what can be tolerated for the application. Using reconstructed maps from small separation mock surveys, the protocluster candidate purity and completeness are very close to what was found in the noiseless case, As the sightline separation increases, the purity and completeness decrease, although they remain much higher than initially expected. Extend test cases to mock surveys with an average separation of 15 Mpc/h, meant to reproduce high source density areas of the BOSS survey. Find that even with such a large sightline separation, the method can still be used to find some f the largest protoclusters.
Day 799
Thursday.
1412.1081
Impact of anisotropic stress of free-streaming particles on gravitational waves induced by cosmological density perturbations
Saga, Ichiki, Sugiyama
GWs are inevitably induced at second-order in cosmo perturbations through NL couplings with first order scalar perturbations, whose existence is well established by recent cosmological observations. So far, the evolution and the spectrum of the secondary induced GWs have been derived by taking into account the sources of GWs only from the product of first order scalar perturbations. Investigate the effects of purely second-order anisotropic stresses of photons and neutrinos on the evolution of GWs, which have been omitted in the literature. Present a full treatment of the Einstein-Boltzmann system to calculate the spectrum of GWs with anisotropic stress based on the formalism of the cosmo perturbation theory. Find that photon anisotropic stress amplifies the amplitude of GWs by 150, whereas neutrino anisotropic stress suppress that of GWs by about 30 on small scales k>~1.0 h/Mpc. The result is in marked contrast with the case at linear order, where the effect of isotropic stress is damping in amplitude of GWs.
1412.1094 The impact of cosmic variance on simulated weak lensing surveys
Kannawadi, Mandelbaum, Lackner
One major systematic uncertainty in WL is the calibration of WL shape distortions, or shears. Most upcoming surveys plan to test several aspects of their shear estimation algorithms using sophisticated image simulations that include realistic galaxy populations based on high-resolution data from the HST. However, existing datasets from HST over very small cosmological volumes, so cosmic variance could cause the galaxy populations in them to be atypical. A narrow redshift slice from such surveys could e dominated by a single large overdensity or under density. In this case, the morphology-density relation could alter the local galaxy populations and yield an incorrect calibration of shear estimates as a function of redshift. Directly test this scenario using the COSMOS survey, the largest-area HST survey to date, and show how the statistical distributions of galaxy shapes and morphological parameters (e.g., Sersic n) are influenced by redshift-dependent cosmic variance. The typical variation in RMS ellipticity due to environmental effects is 5% (absolute, not relative) for redshift bins of width Delta z = 0.05, which could result in uncertain shear calibration at the 1% level. Conclude that the cosmic variance effects are large enough to exceed the systematic error budget of future surveys, but can be mitigated with careful choice of training dataset and sufficiently large redshift binning.
A bunch of ASTRO-H white papers, a JAXA/NASA X-ray satellite.
1412.1239
Cosmic evolution of dust in galaxies: methods and preliminary results
Bekki
Investigate the z evolution of dust properties, its dependences on initial conditions of galaxy formation, and physical correlations between dust, gas , and stellar contents at different z based on the original chemodynamical simulations of galaxy formation with dust growth and destruction. In this preliminary investigation, first determine the reasonable ranges of the two most important parameters of dust evolution, i.e., the timescales of dust growth and destruction, by comparing the observed and simulated dust properties and molecular hydrogen H2 content of the Galaxy. Then investigate the z-evolution of dust-to-gas-ratios (D) and, H2 gas fraction (f_H2), and gas-phase chemical abundances(e.g., A_O=12+log(O/H)) in the simulated disk and dwarf galaxies. The principal results are as follows. Both D and f_H2 can rapidly increase during the early dissipative formation of galactic disks (z~2-3) and the z-evolution of these depends on initial mass densities, spin parameters, and masses of galaxies. The observed A_O-D relation can be qualitatively reproduced, but the simulated dispersion of D at a given A_O is smaller. The simulated galaxies with larger total dust masses show larger H2 and stellar masses and higher f_H2. Disk galaxies show negative radial gradients of D and the gradients are steeper for more massive galaxies. Both dust-to-metal ratios and gas-phase [S/Fe] can be significantly different within a single galaxy and between different galaxies at different z, which means that fixed dust-to-metal ratios should not be used in investigating H2 contents and spectral energy distributions of galaxies.
1412.1432
Predicting Alpha Comae Berneices Time of eclipse I: A 26 year binary will eclipse within 2 weeks of 25 January 2015
Muterspaugh, Henry
As the title says. Keep an eye out for the occultation!
1412.1081
Impact of anisotropic stress of free-streaming particles on gravitational waves induced by cosmological density perturbations
Saga, Ichiki, Sugiyama
GWs are inevitably induced at second-order in cosmo perturbations through NL couplings with first order scalar perturbations, whose existence is well established by recent cosmological observations. So far, the evolution and the spectrum of the secondary induced GWs have been derived by taking into account the sources of GWs only from the product of first order scalar perturbations. Investigate the effects of purely second-order anisotropic stresses of photons and neutrinos on the evolution of GWs, which have been omitted in the literature. Present a full treatment of the Einstein-Boltzmann system to calculate the spectrum of GWs with anisotropic stress based on the formalism of the cosmo perturbation theory. Find that photon anisotropic stress amplifies the amplitude of GWs by 150, whereas neutrino anisotropic stress suppress that of GWs by about 30 on small scales k>~1.0 h/Mpc. The result is in marked contrast with the case at linear order, where the effect of isotropic stress is damping in amplitude of GWs.
1412.1094 The impact of cosmic variance on simulated weak lensing surveys
Kannawadi, Mandelbaum, Lackner
One major systematic uncertainty in WL is the calibration of WL shape distortions, or shears. Most upcoming surveys plan to test several aspects of their shear estimation algorithms using sophisticated image simulations that include realistic galaxy populations based on high-resolution data from the HST. However, existing datasets from HST over very small cosmological volumes, so cosmic variance could cause the galaxy populations in them to be atypical. A narrow redshift slice from such surveys could e dominated by a single large overdensity or under density. In this case, the morphology-density relation could alter the local galaxy populations and yield an incorrect calibration of shear estimates as a function of redshift. Directly test this scenario using the COSMOS survey, the largest-area HST survey to date, and show how the statistical distributions of galaxy shapes and morphological parameters (e.g., Sersic n) are influenced by redshift-dependent cosmic variance. The typical variation in RMS ellipticity due to environmental effects is 5% (absolute, not relative) for redshift bins of width Delta z = 0.05, which could result in uncertain shear calibration at the 1% level. Conclude that the cosmic variance effects are large enough to exceed the systematic error budget of future surveys, but can be mitigated with careful choice of training dataset and sufficiently large redshift binning.
A bunch of ASTRO-H white papers, a JAXA/NASA X-ray satellite.
1412.1239
Cosmic evolution of dust in galaxies: methods and preliminary results
Bekki
Investigate the z evolution of dust properties, its dependences on initial conditions of galaxy formation, and physical correlations between dust, gas , and stellar contents at different z based on the original chemodynamical simulations of galaxy formation with dust growth and destruction. In this preliminary investigation, first determine the reasonable ranges of the two most important parameters of dust evolution, i.e., the timescales of dust growth and destruction, by comparing the observed and simulated dust properties and molecular hydrogen H2 content of the Galaxy. Then investigate the z-evolution of dust-to-gas-ratios (D) and, H2 gas fraction (f_H2), and gas-phase chemical abundances(e.g., A_O=12+log(O/H)) in the simulated disk and dwarf galaxies. The principal results are as follows. Both D and f_H2 can rapidly increase during the early dissipative formation of galactic disks (z~2-3) and the z-evolution of these depends on initial mass densities, spin parameters, and masses of galaxies. The observed A_O-D relation can be qualitatively reproduced, but the simulated dispersion of D at a given A_O is smaller. The simulated galaxies with larger total dust masses show larger H2 and stellar masses and higher f_H2. Disk galaxies show negative radial gradients of D and the gradients are steeper for more massive galaxies. Both dust-to-metal ratios and gas-phase [S/Fe] can be significantly different within a single galaxy and between different galaxies at different z, which means that fixed dust-to-metal ratios should not be used in investigating H2 contents and spectral energy distributions of galaxies.
1412.1432
Predicting Alpha Comae Berneices Time of eclipse I: A 26 year binary will eclipse within 2 weeks of 25 January 2015
Muterspaugh, Henry
As the title says. Keep an eye out for the occultation!
Wednesday, December 3, 2014
Day 798
Wednesday.
1412.0655
Confirmation of a steep luminosity function for Lyman-alpha Emitters at z=5.7: a major component of reionization
Dressler, et al
Direct and robust measurement of the faint-end slope of LAE LF at z=5.7. High-res spectroscopy to distinguish high-z LAEs from FG galaxies. All but 2 of the 42 single-emission-line systems are fainter than F=2e-17 erg/s/cm^2, the faintest emission-lines observed for a z=5.7 sample with known completeness. Find 13 LAEs for 29 FG galaxies. Constrain the faint-end slope of LF to 1.95<-alpha<2.35 (1 sigma). Show how this steep LF should provide, to the limit of the observations, more than 20% of the flux necessary to maintain ionization at z=5.7, with a factor -of-ten extrapolation in flux reaching more than 55%. Suggest that this bodes well for a comparable contribution by similar, low-mass SF galaxies at higher-z - within the reionization epoch at z>7, only 250 Myr earlier - and that such systems provide a substantial, if not dominant, contribution to the late-stage reionization of the IGM.
1412.0657
Maximum speed of hypervelocity stars ejected from binaries
Tauris
The recent detection of HVSs as late-type B-stars and HVS candidate G/K dwarfs raises the important question of their origin. In this Letter, investigate the maximum possible velocities of such HVSs if they are produced from binaries which are disrupted via an asymmetric SN explosion. Find that HVSs up to ~770 km/s and ~1280 km/s are possible in the Galactic rest frame from this scenario for these two subclasses of HVSs, respectively. Conclude that whereas a binary origin cannot easily explain all of the observed velocities of B-type HVSs (in agreement with their proposed central massive BH origin) it can indeed account for the far majority (if not all) of the recently detected G/K-dwaf HVS candidates.
1412.0661
Cosmological simulations of galaxy formation with cosmic rays
Salem, Bryan, Hummels
Investigate the dynamical impact of CRs in cosmo sims of galaxy formation using AMR of 1e12 Msun halo. In agreement with previous work, a run with only the standard thermal energy feedback model results in a massive spheroid and unrealistically peaked rotation curves. However, the addition of a simple two-fluid model for CRs drastically cages the morphology of the forming disk. Include an isotropic diffuse term and a source term tied to SF dues to (unresolved) SN-driven shocks Over a wide range of diffusion coefficients, the CRs generate thin, extended disks with a significantly more realistic (though still not flat) rotation curve. Find that the diffusion of CRs is key to this process, as they escape dense SF clumps and drive outflows within the more diffuse ISM.
1412.0662
The physical nature of cosmic accretion of baryons and dark matter into haloes and their galaxies
Wetzel, Nagai
Cosmic accretion of both DM and baryons drives the formation and evolution of haloes and the galaxies within them. Cosmic accretion for haloes typically is measured using some evolving viral relation, but a recent work suggests that most inferred halo growth at late cosmic time (z<2) is not physical but rather is the byproduct of a viral radius that evolves according to the BG cosmic density ("pseudo-evolution"). This raises the question: how much physical accretion of baryons do haloes experience to fuel SF and growth of the galaxy inside? Using Omega25, a suite of cosmo sims that incorporate both DM and gas dynamics with differing treatments of gas cooling, SF and thermal feedback, explore systematically the physics that governs cosmic accretion into haloes and their galaxies. Physically meaningful cosmic accretion of both DM and baryons occurs at z>1 across the halo mass range: M_200m=1e11-14 Msun. However, DM, being dissipationless, is deposited (in a time-average sense) at >~R_200m in a shell-like matter, such that DM mass and density experience little-to-no physical growth at any radius within a halo at z<1. By contrast, gas, being able to cool radiatively, experiences significant accretion at all radii, at a rate that roughly tracks the accretion rate at R_200m, at all redshifts. Infalling gas starts to decouple from DM at ~1 R_200m and continues to accrete to smaller radii until the onset of strong angular-momentum support at ~0.1 R_200m. Thus, while the growth of DM is subject to pseudo-evolution, the growth of baryons is not. This difference provides insight into the tight relations between galaxies and their host haloes across cosmic time.
1412.0757
Cosmology constraints from the weak lensing peak counts and the power spectrum in CFHTLenS
Liu, Petri, Haiman, Hui, Kratochvil, May
Lensing peaks have been proposed as a useful statistic, containing cosmological info from non-Gaussianities that is inaccessible from traditional 2pt statistics such as the PS or 2PCF. Examine constraints on cosmo parameters from WL peak counts, using publicly available data from CFHTLenS survey. Utilize a new suite of ray-tracing N-body sims on a grid of 91 cosmo models, covering broad ranges of 3 parameters Omega_m, sigma_8, and w, and replicating the galaxy sky positions, z, and shape noise in the CHFTLenS observations. Then build an emulator that interpolates the PS and the peak counts to an accuracy of <=5%, and compute the likelihood in the 3-d parameter space (Omega_m, sigma_8, w) from both observables. Find that constraints from peak counts are comparable to those from the PS, and somewhat tighter when different smoothing scales are combined. Neither observable can constrain w without external data. When the PS and peak counts are combined, the area of the error "banana" in the (Omega_m, sigma_8) plane reduces by a factor of ~2, compared to using the PS alone. For a flat Lambda CDM, combining both statistics, obtain the constraint sigma_8(Omega_m/0.27)^0.63 = 0.78(+0.07,-0.03).
1412.0655
Confirmation of a steep luminosity function for Lyman-alpha Emitters at z=5.7: a major component of reionization
Dressler, et al
Direct and robust measurement of the faint-end slope of LAE LF at z=5.7. High-res spectroscopy to distinguish high-z LAEs from FG galaxies. All but 2 of the 42 single-emission-line systems are fainter than F=2e-17 erg/s/cm^2, the faintest emission-lines observed for a z=5.7 sample with known completeness. Find 13 LAEs for 29 FG galaxies. Constrain the faint-end slope of LF to 1.95<-alpha<2.35 (1 sigma). Show how this steep LF should provide, to the limit of the observations, more than 20% of the flux necessary to maintain ionization at z=5.7, with a factor -of-ten extrapolation in flux reaching more than 55%. Suggest that this bodes well for a comparable contribution by similar, low-mass SF galaxies at higher-z - within the reionization epoch at z>7, only 250 Myr earlier - and that such systems provide a substantial, if not dominant, contribution to the late-stage reionization of the IGM.
1412.0657
Maximum speed of hypervelocity stars ejected from binaries
Tauris
The recent detection of HVSs as late-type B-stars and HVS candidate G/K dwarfs raises the important question of their origin. In this Letter, investigate the maximum possible velocities of such HVSs if they are produced from binaries which are disrupted via an asymmetric SN explosion. Find that HVSs up to ~770 km/s and ~1280 km/s are possible in the Galactic rest frame from this scenario for these two subclasses of HVSs, respectively. Conclude that whereas a binary origin cannot easily explain all of the observed velocities of B-type HVSs (in agreement with their proposed central massive BH origin) it can indeed account for the far majority (if not all) of the recently detected G/K-dwaf HVS candidates.
1412.0661
Cosmological simulations of galaxy formation with cosmic rays
Salem, Bryan, Hummels
Investigate the dynamical impact of CRs in cosmo sims of galaxy formation using AMR of 1e12 Msun halo. In agreement with previous work, a run with only the standard thermal energy feedback model results in a massive spheroid and unrealistically peaked rotation curves. However, the addition of a simple two-fluid model for CRs drastically cages the morphology of the forming disk. Include an isotropic diffuse term and a source term tied to SF dues to (unresolved) SN-driven shocks Over a wide range of diffusion coefficients, the CRs generate thin, extended disks with a significantly more realistic (though still not flat) rotation curve. Find that the diffusion of CRs is key to this process, as they escape dense SF clumps and drive outflows within the more diffuse ISM.
1412.0662
The physical nature of cosmic accretion of baryons and dark matter into haloes and their galaxies
Wetzel, Nagai
Cosmic accretion of both DM and baryons drives the formation and evolution of haloes and the galaxies within them. Cosmic accretion for haloes typically is measured using some evolving viral relation, but a recent work suggests that most inferred halo growth at late cosmic time (z<2) is not physical but rather is the byproduct of a viral radius that evolves according to the BG cosmic density ("pseudo-evolution"). This raises the question: how much physical accretion of baryons do haloes experience to fuel SF and growth of the galaxy inside? Using Omega25, a suite of cosmo sims that incorporate both DM and gas dynamics with differing treatments of gas cooling, SF and thermal feedback, explore systematically the physics that governs cosmic accretion into haloes and their galaxies. Physically meaningful cosmic accretion of both DM and baryons occurs at z>1 across the halo mass range: M_200m=1e11-14 Msun. However, DM, being dissipationless, is deposited (in a time-average sense) at >~R_200m in a shell-like matter, such that DM mass and density experience little-to-no physical growth at any radius within a halo at z<1. By contrast, gas, being able to cool radiatively, experiences significant accretion at all radii, at a rate that roughly tracks the accretion rate at R_200m, at all redshifts. Infalling gas starts to decouple from DM at ~1 R_200m and continues to accrete to smaller radii until the onset of strong angular-momentum support at ~0.1 R_200m. Thus, while the growth of DM is subject to pseudo-evolution, the growth of baryons is not. This difference provides insight into the tight relations between galaxies and their host haloes across cosmic time.
1412.0757
Cosmology constraints from the weak lensing peak counts and the power spectrum in CFHTLenS
Liu, Petri, Haiman, Hui, Kratochvil, May
Lensing peaks have been proposed as a useful statistic, containing cosmological info from non-Gaussianities that is inaccessible from traditional 2pt statistics such as the PS or 2PCF. Examine constraints on cosmo parameters from WL peak counts, using publicly available data from CFHTLenS survey. Utilize a new suite of ray-tracing N-body sims on a grid of 91 cosmo models, covering broad ranges of 3 parameters Omega_m, sigma_8, and w, and replicating the galaxy sky positions, z, and shape noise in the CHFTLenS observations. Then build an emulator that interpolates the PS and the peak counts to an accuracy of <=5%, and compute the likelihood in the 3-d parameter space (Omega_m, sigma_8, w) from both observables. Find that constraints from peak counts are comparable to those from the PS, and somewhat tighter when different smoothing scales are combined. Neither observable can constrain w without external data. When the PS and peak counts are combined, the area of the error "banana" in the (Omega_m, sigma_8) plane reduces by a factor of ~2, compared to using the PS alone. For a flat Lambda CDM, combining both statistics, obtain the constraint sigma_8(Omega_m/0.27)^0.63 = 0.78(+0.07,-0.03).
Monday, December 1, 2014
Day 797
Tuesday.
1412.0178
An observational signal of the void shape correlation and its link to the cosmic web
Lee, Hoyle
The shapes of cosmic voids are prone to distortions by the external tidal forces since their low-densities imply a lower internal resistance. This susceptibility of the void shapes to the tidal distortions makes them useful as an indicator of the large-scale tidal and density fields, despite the practical difficulty in defining them. Using the void catalog by Pan+2012 from SDSS DR7, detect a clear 4 sigma signal of spatial correlations of the void shapes on the scale of 20 Mpc/h and show that the signal is robust against the projection of the void shapes onto the plane of sky. By constructing a simple analytic model for the void shape correlation, within the framework of tidal torque theory, demonstrate that the void shape correlation function scales linearly with the 2PCF of the linear density field. Also find a direct observational evidence for the cross-correlation of the void shapes wit the large-scale velocity shear field that was linearly reconstructed by Lee+2014 from DR7. Discuss the possibility of using the void shape correlation function to break the degeneracy between the density parameter and the power spectrum amplitude and to independently constrain the neutrino mass as well.
1412.0592
Constraints on massive neutrinos from the pairwise kinematic Sunyaev-Zel'dovich effect
Mueller, de Bernardis, Bean, Niemack
Central to the constraints is a distinctive scale dependence of the kSZ neutrino signature on the mean pairwise momentum of clusters that is not expected to be mirrored in systematic effects that change the overall amplitude of the signal, like the cluster optical depth. Forecasts.
1412.0626
The Atacama Cosmology Telescope: lensing of CMB temperature and polarization derived from Cosmic Infrared Background Cross-Correlation
ven Engelen, Sherwin, Sehgal, ... et al
Present a measurement of the gravitational lensing of CMB temperature and polarizattion fields obtained by cross-correlating the reconstructed convergence signal from the first season of ACTPol data, with CIB fluctuations measured using the Planck satellite. Using an overlap area of 206 sq deg, detect gravitational lensing of the CMB polarization by large-scale structure at a statistical significance of 4.5 sigma. Combining both CMB temperature and polarization data gives a lensing detection at 9.1 sigma significance. A B-mode polarization lensing signal is present with a significance of 3.2 sigma. Also present the first measurement of CMB lensing-CIB correlation at small scales corresponding to ell > 2000. Null tests and systematic checks show that the results are not significantly biased by astrophysical or instrumental systematic effects, including Galactic dust. Fitting measurements to the best-fit lensing-CIB cross PS measured in Planck data, scaled by an amplitude A, gives A = 1.02pm0.02, consistent with the Planck results.
1412.0178
An observational signal of the void shape correlation and its link to the cosmic web
Lee, Hoyle
The shapes of cosmic voids are prone to distortions by the external tidal forces since their low-densities imply a lower internal resistance. This susceptibility of the void shapes to the tidal distortions makes them useful as an indicator of the large-scale tidal and density fields, despite the practical difficulty in defining them. Using the void catalog by Pan+2012 from SDSS DR7, detect a clear 4 sigma signal of spatial correlations of the void shapes on the scale of 20 Mpc/h and show that the signal is robust against the projection of the void shapes onto the plane of sky. By constructing a simple analytic model for the void shape correlation, within the framework of tidal torque theory, demonstrate that the void shape correlation function scales linearly with the 2PCF of the linear density field. Also find a direct observational evidence for the cross-correlation of the void shapes wit the large-scale velocity shear field that was linearly reconstructed by Lee+2014 from DR7. Discuss the possibility of using the void shape correlation function to break the degeneracy between the density parameter and the power spectrum amplitude and to independently constrain the neutrino mass as well.
1412.0592
Constraints on massive neutrinos from the pairwise kinematic Sunyaev-Zel'dovich effect
Mueller, de Bernardis, Bean, Niemack
Central to the constraints is a distinctive scale dependence of the kSZ neutrino signature on the mean pairwise momentum of clusters that is not expected to be mirrored in systematic effects that change the overall amplitude of the signal, like the cluster optical depth. Forecasts.
1412.0626
The Atacama Cosmology Telescope: lensing of CMB temperature and polarization derived from Cosmic Infrared Background Cross-Correlation
ven Engelen, Sherwin, Sehgal, ... et al
Present a measurement of the gravitational lensing of CMB temperature and polarizattion fields obtained by cross-correlating the reconstructed convergence signal from the first season of ACTPol data, with CIB fluctuations measured using the Planck satellite. Using an overlap area of 206 sq deg, detect gravitational lensing of the CMB polarization by large-scale structure at a statistical significance of 4.5 sigma. Combining both CMB temperature and polarization data gives a lensing detection at 9.1 sigma significance. A B-mode polarization lensing signal is present with a significance of 3.2 sigma. Also present the first measurement of CMB lensing-CIB correlation at small scales corresponding to ell > 2000. Null tests and systematic checks show that the results are not significantly biased by astrophysical or instrumental systematic effects, including Galactic dust. Fitting measurements to the best-fit lensing-CIB cross PS measured in Planck data, scaled by an amplitude A, gives A = 1.02pm0.02, consistent with the Planck results.
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