Wednesday.
1112.1956
Galaxy and mass assembly (GAMA): structural investigation of galaxies via model analysis (SIGMA)
Kelvin, ... et al
Present single Sérsic 2d model fits to 167k galaxies modeled independently in the ugrizYJHK bandpasses using SDSS DR7 and UKIDSS-LAS imaging data available from GAMA database. Developed SIGMA, an R wrapper around several astronomy SW packages including SExtractor, PSF Extractor and GALFIT 3. SIGMA produces realistic 2d model fits to galaxies, employing automatic adaptive BG subtraction and empirical PSF measurements on the fly for each galaxy in GAMA. Using these results, define a common coverage area across the 3 GAMA regions containing 138k galaxies. Provide Sersic magnitudes truncated at 10 re which show good agreement with SDSS Petrosian and GAMA photometry for low Sersic index systems (n<4), and much improved photometry for high Sersic index systems (n>4), recovering as much as Delta m=0.5 magnitudes in the r band. Employ a K band Sersic index / u-r color relation to delineate the massive (n>~2) ETGs from the LTGs. The mean Sersic index of these ETGs shows a smooth variation with wavelength, increasing by 30% from g through K. LTGs exhibit a more extreme change in Sersic index, increasing by 52% across the same range. In addition, ETGs and LTGs exhibit a 38% and 25% decrease respectively in HLR from g through K. These trends are shown to arise due to the effects of dust attenuation and stellar population/metallicity gradients within galaxy populations.
1407.7545
Impact of population~III binaries on early cosmic evolution
Chen, Bromm, Heger, Jeon, Woosley
Present the results of the stellar feedback from Pop III binaries. Consider a fixed mass of 60 Msun, either contained in a single star, or split up in binary stars of 30 Msun each, or asymmetric case of 45 Msun and 15 Msun. Where as the sizes of the resulting HII regions are comparable across all cases, the HeIII regions around binary stars are significantly smaller than that of the single star. Consequently, the He+ 1640 A recombination line is expected to become much weaker. SN feedback exhibits great variety due to the uncertainty in possible explosion pathways. If at least one of the component stars dies as a hyper nova about 10 times more energetic that conventional core-collapse SNe, the gas inside the host mini halo is effectively blown out, chemically enriching the IGM to an average metallicity of 1e-4 to 1e-3 Zsun, out to ~2 kpc. The single star, however, is more likely to collapse into a BH, accompanied by at most very weak explosions. The effectiveness of early chemical enrichment would thus be significantly reduced, in difference from the lower mass binary stars, where at least one component is likely to contribute to heavy element production and dispersal. Important new feedback physics is also introduced if close binaries can form high-mass x-ray binaries, leading to the pre-heating and ionization of the IGM beyond the extent of the stellar HII regions.
1407.7555
Galaxy and mass assembly (GAMA): stellar mass functions by Hubble type
Kelvin, et al
Present an estimate of the galaxy stellar MF and its division by morphological type in the local (0.025<z<0.06) universe. From a sample of 3727 galaxies from GAMA, define a local volume and stellar mass limited sub-sample of 2711 galaxies to a lower stellar mass limit of M=1e9Msun. Confirm that the galaxy stellar MF is well described by a double Schechter function, with alpha1=-0.43 and alpha2=-1.50 (M*=1e10.6Msun, phi*1=4.1/dex/Mpc3, phi*2=0.74 /dex/Mpc3). The constituent morphological-type stellar MFs are well sampled above the lower stellar mass limit, excepting the faint little blue spheroid population of galaxies. Find approximately 71% of the stellar mass in the local Universe within spheroid dominated galaxies (ellipticals and S0-Sas). The remaining 29% falls predominantly within late type disk dominated systems, Sab-Scds and Sd-Irrs. Adopting reasonable bulge-to-total ratios implies that approximately half the stellar mass today resides in spheroidal structures, and half in disk structures. Within this local sample, find approximate stellar mass proportions for E : S0-Sa : Sab-Scd : Sd-Irr of 34 : 37 : 24 : 5.
1407.7676
GalSim: the modular galaxy image simulation toolkit
Rowe, et al
GALSIM: SW library of generating images of astronomical objects such as stars and galaxies, efficiently handling image transformations and operations such as convolution and rendering at high precision. Demonstrate that the performance of GALSIM meets the stringent requirements of high precision image analysis applications such as WL for current datasets and for the Stage IV DE surveys of LSST, Euclid, WFIRST-AFTA. The GALSIM project repository is public and includes the full code history, all open and closed issues, installation instructions, documentation, and wiki pages.
Tuesday, July 29, 2014
Monday, July 28, 2014
Day 711
Tuesday.
1407.7030
Star formation at $4<z<6$ from the Spitzer large area survey with Hyper-Suprime-Cam (SPLASH)
Steinhardt, et al
Estimate the masses and SFRs of 3396 M*>1e10Msun SF galaxies at 4<z<6 with a substantial population up to M*>1e11.5Msun. Find that the strong correlation between stellar mass and SFR seen at lower z (the "main sequence" of SF galaxies) extends to z~6. The observed relation and scatter is consistent wit ha continued increase in SFR at fixed mass in line with extrapolations from lower-redshift observations. It is difficult to explain this continued correlation, especially for the most massive systems, unless the most massive galaxies are forming stars near their Eddington-limited rate from their first collapse. Furthermore, find no evidence for moderate quenching at higher masses, indicating quenching either has not occurred prior to z~6 or else occurs rapidly, so that few galaxies are visible in transition between SF and quenched.
1407.7032
Planet Formation Imager (PFI): introduction and technical considerations
Monnier, et al
The aim of the PFI project is to develop the roadmap for the construction of a new near-/mid-IR interferometric facility that will be optimized to unmask all the major stages of planet formation, from initial dust coagulation, gap formation, evolution of transition disks, mass accretion onto planetary embryos, and eventual disk dispersal. High resolution imaging at a range of wavelengths will give a glimpse and enable a robust theoretical framework for predicting planetary system architectures around a range of stars surrounded by disks with a diversity of initial conditions Only long-baseline interferometry can provide the needed angular resolution and wavelength coverage to reach these goals. PFI will be able to detect the emission of the cooling, newly-formed planets themselves over the first 100 Myrs, opening up both spectral investigations and also providing a vibrant look into the early dynamical histories of planetary architectures. Introduce the PFI project and give initial thoughts on possible facility architectures and technical advances that will be needed to meet the challenging top-level science requirements.
1407.7039
Galactic r-process enrichment by neutron star mergers in cosmological simulations of a Milky Way-mass galaxy
van de Voort, Quataert, Hopkins, Keres, Faucher-Giguere
Using cosmological zoom-in simulations of MW-mass galaxy, quantify the stellar abundances of neutron-rich r-process nuclei. The galaxy is enriched with r-process elements by binary NS mergers and with Fe and other metals by SNe. These calculations include key hydrodynamic mixing processes not present in standard semi-analytic chemical evolution models, such as galactic winds and hydrodynamic flows associated with structure formation. Explore a range of models for the rate and delay time of NS mergers, intended to roughly bracket the wide range of models consisted wit current observational constraints. Show that NS mergers can produce [r-process/Fe] abundance ratios and scatter that appear reasonably consistent with observational constraints. At low metallicity, [Fe/H]<-2, predict there is a wide range of stellar r-process abundance ratios, with both super solar and subsloar abundances. Low-metallicit stars or stars that are outliers in their r-process abundance rations are, on average, formed at high z and located at large galactocentric radius. Because NS mergers are rare, results are not fully converged wrt resolution, particularly at low metallicity. However, the uncertain rate and delay time distribution of NS mergers introduces an uncertainty in the r-process abundances comparable to that due to finite numerical resolution. Overall, results are consistent with NS mergers being the source of most of the r-process nuclei in the Universe.
1407.7040
The EAGLE project: simulating the volition and assembly of galaxies and their environments
Schaye, .. Bower, .. White, .. Navarro, .. et al
Introduce the Virgo Consortium's EAGLE project, a suite of hydro sims that follow the formation of galaxies and black holes in representative volumes. Limitations due to resolution discussed. Major improvement is the treatment of feedback from massive stars and AGN in which thermal energy is injected into the gas without the need to turn off cooling or hydrodynamical forces, allowing winds to develop without predetermined speed or mass loading factors. Because the feedback efficiencies cannot be predicted from first principles, calibrate them to the z~0 galaxy stellar MF and the amplitude of the galaxy-central BH mass relation, also taking galaxies sizes into account. The observed galaxy MF is reproduced to <0.2 dex over the full mass range, 1e8<M*/Msun<1e11, a level of agreement close to that attained by semi-analytic models, and unprecedented for hydrodynamical simulations. Compare results to a representative set of low-z observables not considered in the calibrations, and find good agreement with the observed galaxy sSFRs, passive fractions, TF relation, total stellar luminosities of galaxy clusters, and column density distributions of intergalactic CIV and OVI. While the mass-metallicity relations for gas and stars are consistent with observations for M*>1e9 Msun, they are insufficiently steep at lower masses. The gas fractions and temperatures are too high for clusters of galaxies, but for groups there discrepancies can be resolved by adopting a higher heating temperature in the sub grid prescription for AGN feedback. EAGLE constitutes a valuable new resources for studies of galaxy formation.
1407.7129
Four phases of angular-momentum buildup in high-z galaxies: from cosmic-web streams to an extended titled ring, disk and bulge
Danovich, Dekel, Hahn, Ceverino, Primack
Study the buildup of angular momentum (AM) in high-z galaxies using zoom-in hydro-cosmo sims. The disk AM originates in a few co-planar streams of cold gas and merging galaxies tracing filaments of the cosmic web and undergo 4 phases of evolution. In phase I, outside the halo virial radius (Rv), the elongated streams gain AM by tidal torques with a specific AM (sAM) ~1.7 times that of the DM due to gas' higher quadrupole moment. This AM is expressed as stream impact parameters, from ~0.3 Rv to occasional counter rotation. In phase II, in the outer halo, while the incoming DM mixes with the existing halo of lower sAM to a spin lambda_dm~0.04, the cold streams transport the AM to the inner halo such that their spin in the halo is ~3 lambda_dm. In phase III, near pericenter, the streams dissipate and form a non-uniform, rotating ring extending to ~0.3 Rv and tilted relative to the inner disc. Torques exerted partly by the disc make the gas ring lose AM, spiral in, and settle into the disc within one orbit. The ring is observable with 30% probability as a damped Lyman-alpha absorber. In phase IV, within the disc, torques associated with violent disc instability drive AM out and baryons into a central bulge, while outflows remove low-spin gas. Despite the different AM histories of gas and DM, the spin of the disc is only moderately smaller that that of the DM halo.
1407.7316
Measurement of galaxy clustering at z~7.2 and the evolution of galaxy bias from 3.8<z<8 in the XDF, GOODS-S and GOODS-N
Barone-Nugent, ... Oesch, ... van Dokkum, et al
N=743 LBG candidates at z>6.5 at a mean redshift of z=7.2 from various surveys. Detect a clear clustering signal in the angular correlation function (ACF) at ~4sigma, corresponding to a real-space correlation length r_0=6.7pm1 cMpc/h. The derived galaxy bias b=8.6pm1 is that of DM haloes of M=1e11 Msun at z=7.2, and highlights that galaxies below the current detection limit (M_AB~-17.7) are expected in lower mass haloes (M~1e8-10.5 Msun). Compute the ACF of LBGs at z~3.8-5.9 in the same surveys. A trend of increasing bias is found from z=3.8 (b~3.0) to z=7.2 (b~8.6), broadly consistent with galaxies at fixed luminosity being hosted in DM haloes of similar mass at 4<z<6, followed by a slight rise in halos masses at z~7 (~2 sigma confidence). Separating the data at the median luminosity of the z=7.2 sample (M_UV=-19.4) shows higher clustering at z=5.9 for bright galaxies (b=6.2) compared to faint galaxies (b=2.7) implying a constant M/L ratio dlogM/dlogL~1.2p1.8m0.5. A similar trend is present n the z=7.2 sample with larger uncertainty. Finally, bias measurements allow us to investigate the fraction of DM haloes hosting UV-bright galaxies (the duty-cycle). At z=7.2 values near unity are preferred, which may be explained by the shortened halo assembly time at high-redshift.
1407.7335
The SAMI galaxy survey: instrument specification and target selection
Bryant, et al
Integral-field spectrograph survey of 3400 galaxies in the GAMA region.
1407.7364
On the local variation of the Hubble constant
Odderskov, Hannestad, Haugbølle
From N-body sims: the expected variance in measurements of H0 is far too small to explain the current discrepancy between the low value of H0 inferred from measurements of CMB and Type Ia SNe.
1407.7030
Star formation at $4<z<6$ from the Spitzer large area survey with Hyper-Suprime-Cam (SPLASH)
Steinhardt, et al
Estimate the masses and SFRs of 3396 M*>1e10Msun SF galaxies at 4<z<6 with a substantial population up to M*>1e11.5Msun. Find that the strong correlation between stellar mass and SFR seen at lower z (the "main sequence" of SF galaxies) extends to z~6. The observed relation and scatter is consistent wit ha continued increase in SFR at fixed mass in line with extrapolations from lower-redshift observations. It is difficult to explain this continued correlation, especially for the most massive systems, unless the most massive galaxies are forming stars near their Eddington-limited rate from their first collapse. Furthermore, find no evidence for moderate quenching at higher masses, indicating quenching either has not occurred prior to z~6 or else occurs rapidly, so that few galaxies are visible in transition between SF and quenched.
1407.7032
Planet Formation Imager (PFI): introduction and technical considerations
Monnier, et al
The aim of the PFI project is to develop the roadmap for the construction of a new near-/mid-IR interferometric facility that will be optimized to unmask all the major stages of planet formation, from initial dust coagulation, gap formation, evolution of transition disks, mass accretion onto planetary embryos, and eventual disk dispersal. High resolution imaging at a range of wavelengths will give a glimpse and enable a robust theoretical framework for predicting planetary system architectures around a range of stars surrounded by disks with a diversity of initial conditions Only long-baseline interferometry can provide the needed angular resolution and wavelength coverage to reach these goals. PFI will be able to detect the emission of the cooling, newly-formed planets themselves over the first 100 Myrs, opening up both spectral investigations and also providing a vibrant look into the early dynamical histories of planetary architectures. Introduce the PFI project and give initial thoughts on possible facility architectures and technical advances that will be needed to meet the challenging top-level science requirements.
1407.7039
Galactic r-process enrichment by neutron star mergers in cosmological simulations of a Milky Way-mass galaxy
van de Voort, Quataert, Hopkins, Keres, Faucher-Giguere
Using cosmological zoom-in simulations of MW-mass galaxy, quantify the stellar abundances of neutron-rich r-process nuclei. The galaxy is enriched with r-process elements by binary NS mergers and with Fe and other metals by SNe. These calculations include key hydrodynamic mixing processes not present in standard semi-analytic chemical evolution models, such as galactic winds and hydrodynamic flows associated with structure formation. Explore a range of models for the rate and delay time of NS mergers, intended to roughly bracket the wide range of models consisted wit current observational constraints. Show that NS mergers can produce [r-process/Fe] abundance ratios and scatter that appear reasonably consistent with observational constraints. At low metallicity, [Fe/H]<-2, predict there is a wide range of stellar r-process abundance ratios, with both super solar and subsloar abundances. Low-metallicit stars or stars that are outliers in their r-process abundance rations are, on average, formed at high z and located at large galactocentric radius. Because NS mergers are rare, results are not fully converged wrt resolution, particularly at low metallicity. However, the uncertain rate and delay time distribution of NS mergers introduces an uncertainty in the r-process abundances comparable to that due to finite numerical resolution. Overall, results are consistent with NS mergers being the source of most of the r-process nuclei in the Universe.
1407.7040
The EAGLE project: simulating the volition and assembly of galaxies and their environments
Schaye, .. Bower, .. White, .. Navarro, .. et al
Introduce the Virgo Consortium's EAGLE project, a suite of hydro sims that follow the formation of galaxies and black holes in representative volumes. Limitations due to resolution discussed. Major improvement is the treatment of feedback from massive stars and AGN in which thermal energy is injected into the gas without the need to turn off cooling or hydrodynamical forces, allowing winds to develop without predetermined speed or mass loading factors. Because the feedback efficiencies cannot be predicted from first principles, calibrate them to the z~0 galaxy stellar MF and the amplitude of the galaxy-central BH mass relation, also taking galaxies sizes into account. The observed galaxy MF is reproduced to <0.2 dex over the full mass range, 1e8<M*/Msun<1e11, a level of agreement close to that attained by semi-analytic models, and unprecedented for hydrodynamical simulations. Compare results to a representative set of low-z observables not considered in the calibrations, and find good agreement with the observed galaxy sSFRs, passive fractions, TF relation, total stellar luminosities of galaxy clusters, and column density distributions of intergalactic CIV and OVI. While the mass-metallicity relations for gas and stars are consistent with observations for M*>1e9 Msun, they are insufficiently steep at lower masses. The gas fractions and temperatures are too high for clusters of galaxies, but for groups there discrepancies can be resolved by adopting a higher heating temperature in the sub grid prescription for AGN feedback. EAGLE constitutes a valuable new resources for studies of galaxy formation.
1407.7129
Four phases of angular-momentum buildup in high-z galaxies: from cosmic-web streams to an extended titled ring, disk and bulge
Danovich, Dekel, Hahn, Ceverino, Primack
Study the buildup of angular momentum (AM) in high-z galaxies using zoom-in hydro-cosmo sims. The disk AM originates in a few co-planar streams of cold gas and merging galaxies tracing filaments of the cosmic web and undergo 4 phases of evolution. In phase I, outside the halo virial radius (Rv), the elongated streams gain AM by tidal torques with a specific AM (sAM) ~1.7 times that of the DM due to gas' higher quadrupole moment. This AM is expressed as stream impact parameters, from ~0.3 Rv to occasional counter rotation. In phase II, in the outer halo, while the incoming DM mixes with the existing halo of lower sAM to a spin lambda_dm~0.04, the cold streams transport the AM to the inner halo such that their spin in the halo is ~3 lambda_dm. In phase III, near pericenter, the streams dissipate and form a non-uniform, rotating ring extending to ~0.3 Rv and tilted relative to the inner disc. Torques exerted partly by the disc make the gas ring lose AM, spiral in, and settle into the disc within one orbit. The ring is observable with 30% probability as a damped Lyman-alpha absorber. In phase IV, within the disc, torques associated with violent disc instability drive AM out and baryons into a central bulge, while outflows remove low-spin gas. Despite the different AM histories of gas and DM, the spin of the disc is only moderately smaller that that of the DM halo.
1407.7316
Measurement of galaxy clustering at z~7.2 and the evolution of galaxy bias from 3.8<z<8 in the XDF, GOODS-S and GOODS-N
Barone-Nugent, ... Oesch, ... van Dokkum, et al
N=743 LBG candidates at z>6.5 at a mean redshift of z=7.2 from various surveys. Detect a clear clustering signal in the angular correlation function (ACF) at ~4sigma, corresponding to a real-space correlation length r_0=6.7pm1 cMpc/h. The derived galaxy bias b=8.6pm1 is that of DM haloes of M=1e11 Msun at z=7.2, and highlights that galaxies below the current detection limit (M_AB~-17.7) are expected in lower mass haloes (M~1e8-10.5 Msun). Compute the ACF of LBGs at z~3.8-5.9 in the same surveys. A trend of increasing bias is found from z=3.8 (b~3.0) to z=7.2 (b~8.6), broadly consistent with galaxies at fixed luminosity being hosted in DM haloes of similar mass at 4<z<6, followed by a slight rise in halos masses at z~7 (~2 sigma confidence). Separating the data at the median luminosity of the z=7.2 sample (M_UV=-19.4) shows higher clustering at z=5.9 for bright galaxies (b=6.2) compared to faint galaxies (b=2.7) implying a constant M/L ratio dlogM/dlogL~1.2p1.8m0.5. A similar trend is present n the z=7.2 sample with larger uncertainty. Finally, bias measurements allow us to investigate the fraction of DM haloes hosting UV-bright galaxies (the duty-cycle). At z=7.2 values near unity are preferred, which may be explained by the shortened halo assembly time at high-redshift.
1407.7335
The SAMI galaxy survey: instrument specification and target selection
Bryant, et al
Integral-field spectrograph survey of 3400 galaxies in the GAMA region.
1407.7364
On the local variation of the Hubble constant
Odderskov, Hannestad, Haugbølle
From N-body sims: the expected variance in measurements of H0 is far too small to explain the current discrepancy between the low value of H0 inferred from measurements of CMB and Type Ia SNe.
Sunday, July 27, 2014
Day 710
Monday.
1407.6708
The distribution of satellites around central galaxies in a cosmological hydrodynamical simulation
Dong, Lin, Kang, Wang, Dutton, Macciò
Observations have shown that the spatial distribution of satellite galaxies is not random, but rather, it is aligned with the major axes of central galaxies. The strength of the alignment is dependent on the properties of both satellites and centrals. Theoretical studies using dissipation less N-body sims are limited by their inability to directly predict the shape of central galaxies. Using hydrodynamical simulations including gas cooling, SF and feedback, carry out a study of galaxy alignment and its dependence on galaxy properties predicted directly from the simulations. Find that the observed alignment signal is well produced, as is the color dependence: red satellites and red centrals both show stronger alignments than their blue counterparts. The reason for the stronger alignment of red satellites is that most of them stay in the inner region of the dark matter halo, where the shape of central galaxy traces better the DM distribution. The dependence of alignment on the color of central galaxies arises from halo mass dependence, since the alignment between the shape of the central stellar component and the inner halo increases with halo mass. Also find that the alignment of satellites is most strongly dependent on their metallicity, suggesting that the metallicity of satellites, rather than color, is a better tracer of galaxy alignment on small scales. This could be tested in future observational studies.
1407.6715
Quenching depends on morphologies: implications from the ultraviolet-optical color distributions in Green Valley Galaxies
Pan, Li, Lin, Wang, Kong
Analyse the radial UV-optical color distributions in a sample of low redshift GV galaxies, with GALEX+SDSS images, to investigate the residual recent SF distribute in these galaxies. Find that the dust-corrected u-r colors of ETGs are flat out to R_90, while the colors turn blue monotonously when r>0.5R_50 for LTGs. More than a half of the ETGs are blue-cored and have remarkable positive NUV-r color gradients, suggesting that their SF are centrally concentrated; the rest have flat color distributions out to R_90. The centrally concentrated SF activity in a large portion of ETGs is confirmed by the SDSS spectroscopy, showing that ~50% ETGs have EW(Ha)>6.0AA. For the LTGs, 95% of them show uniform radial color profiles, which can be interpreted as a red bulge plus an extended blue disk. The links between the two kinds of ETGs, e.g., those objects having remarkable "blue-cored" and those having flat color gradients, are less known and require future investigations. It is suggested that the LTGs follow a general picture that quenching first occur in the core regions, and then finally extend to the rest of the galaxy. This result can be re-examined and have important implications for the IFU surveys, such as MaNGA and SAMI.
1407.6740
The spatial distribution of satellite galaxies within halos: measuring the very small scale angular clustering of SDSS galaxies
Piscionere, Berlind, McBride, Scoccimarro
Measure the angular clustering of galaxies from SDSS DR7 in order to probe the spatial distribution of satellite galaxies within their DM haloes. Specifically, measure the angular correlation function on very small scales (7-320") in a range of luminosity threshold samples (absolute r-band magnitudes of -18 up to -21) that are constructed from the subset of SDSS that has been spectroscopically observed more than once (plate overlap region). Choose to measure angular clustering in this reduced survey footprint in order to minimize the effects of fiber collision incompleteness, which are otherwise substantial on these small scales. Model clustering measurements using a fully numerical halo model that populates DM haloes in N-body sims to create realistic mock galaxy catalogs. The model has free parameters that specify both the number and spatial distribution of galaxies within their host halos. Adopt a flexible density profile for the spatial distribution of satellite galaxies that is similar to the DM NFW profile, except that the inner slope is allowed to vary. Find that the angular clustering of the most luminous samples (Mr<-20 and -21) suggests that luminous satellite galaxies have substantially steeper inner density profiles than NFW. Lower luminosity samples are less constraining, however, and are consistent with satellite galaxies having shallow density profiles. Results confirm the findings of Watson+2012 while using different clustering measurements and modeling methodology.
1407.6990
The intrinsic alignment of galaxies and its impact on weak gravitational lensing in an era of precision cosmology
Troxel, Ishak
Cosmic shear measures the minute distributions of BG galaxy images by intervening cosmic structure, promising to be a powerful probe of astrophysics and cosmology. However, the IA of galaxies --- their shape and orientation before being lensed --- poses a great challenge to the use of WL as an accurate probe, and has been identified as one of the primary physical systematic biases in cosmic shear studies. Correlations between this IA and the lensing signal can persist even for large physical separations, and isolating the effect of IA from WL is not trivial. Two decades of work in understanding and characterizing IA, which is also a direct and complementary probe of structure formation and evolution in its own right. In this review, report the state of the understanding of IA of galaxies, with a particular emphasis on its large-scale impact on WL measurements and methods for its isolation or mitigation.
1407.6708
The distribution of satellites around central galaxies in a cosmological hydrodynamical simulation
Dong, Lin, Kang, Wang, Dutton, Macciò
Observations have shown that the spatial distribution of satellite galaxies is not random, but rather, it is aligned with the major axes of central galaxies. The strength of the alignment is dependent on the properties of both satellites and centrals. Theoretical studies using dissipation less N-body sims are limited by their inability to directly predict the shape of central galaxies. Using hydrodynamical simulations including gas cooling, SF and feedback, carry out a study of galaxy alignment and its dependence on galaxy properties predicted directly from the simulations. Find that the observed alignment signal is well produced, as is the color dependence: red satellites and red centrals both show stronger alignments than their blue counterparts. The reason for the stronger alignment of red satellites is that most of them stay in the inner region of the dark matter halo, where the shape of central galaxy traces better the DM distribution. The dependence of alignment on the color of central galaxies arises from halo mass dependence, since the alignment between the shape of the central stellar component and the inner halo increases with halo mass. Also find that the alignment of satellites is most strongly dependent on their metallicity, suggesting that the metallicity of satellites, rather than color, is a better tracer of galaxy alignment on small scales. This could be tested in future observational studies.
1407.6715
Quenching depends on morphologies: implications from the ultraviolet-optical color distributions in Green Valley Galaxies
Pan, Li, Lin, Wang, Kong
Analyse the radial UV-optical color distributions in a sample of low redshift GV galaxies, with GALEX+SDSS images, to investigate the residual recent SF distribute in these galaxies. Find that the dust-corrected u-r colors of ETGs are flat out to R_90, while the colors turn blue monotonously when r>0.5R_50 for LTGs. More than a half of the ETGs are blue-cored and have remarkable positive NUV-r color gradients, suggesting that their SF are centrally concentrated; the rest have flat color distributions out to R_90. The centrally concentrated SF activity in a large portion of ETGs is confirmed by the SDSS spectroscopy, showing that ~50% ETGs have EW(Ha)>6.0AA. For the LTGs, 95% of them show uniform radial color profiles, which can be interpreted as a red bulge plus an extended blue disk. The links between the two kinds of ETGs, e.g., those objects having remarkable "blue-cored" and those having flat color gradients, are less known and require future investigations. It is suggested that the LTGs follow a general picture that quenching first occur in the core regions, and then finally extend to the rest of the galaxy. This result can be re-examined and have important implications for the IFU surveys, such as MaNGA and SAMI.
1407.6740
The spatial distribution of satellite galaxies within halos: measuring the very small scale angular clustering of SDSS galaxies
Piscionere, Berlind, McBride, Scoccimarro
Measure the angular clustering of galaxies from SDSS DR7 in order to probe the spatial distribution of satellite galaxies within their DM haloes. Specifically, measure the angular correlation function on very small scales (7-320") in a range of luminosity threshold samples (absolute r-band magnitudes of -18 up to -21) that are constructed from the subset of SDSS that has been spectroscopically observed more than once (plate overlap region). Choose to measure angular clustering in this reduced survey footprint in order to minimize the effects of fiber collision incompleteness, which are otherwise substantial on these small scales. Model clustering measurements using a fully numerical halo model that populates DM haloes in N-body sims to create realistic mock galaxy catalogs. The model has free parameters that specify both the number and spatial distribution of galaxies within their host halos. Adopt a flexible density profile for the spatial distribution of satellite galaxies that is similar to the DM NFW profile, except that the inner slope is allowed to vary. Find that the angular clustering of the most luminous samples (Mr<-20 and -21) suggests that luminous satellite galaxies have substantially steeper inner density profiles than NFW. Lower luminosity samples are less constraining, however, and are consistent with satellite galaxies having shallow density profiles. Results confirm the findings of Watson+2012 while using different clustering measurements and modeling methodology.
1407.6990
The intrinsic alignment of galaxies and its impact on weak gravitational lensing in an era of precision cosmology
Troxel, Ishak
Cosmic shear measures the minute distributions of BG galaxy images by intervening cosmic structure, promising to be a powerful probe of astrophysics and cosmology. However, the IA of galaxies --- their shape and orientation before being lensed --- poses a great challenge to the use of WL as an accurate probe, and has been identified as one of the primary physical systematic biases in cosmic shear studies. Correlations between this IA and the lensing signal can persist even for large physical separations, and isolating the effect of IA from WL is not trivial. Two decades of work in understanding and characterizing IA, which is also a direct and complementary probe of structure formation and evolution in its own right. In this review, report the state of the understanding of IA of galaxies, with a particular emphasis on its large-scale impact on WL measurements and methods for its isolation or mitigation.
Saturday, July 26, 2014
Day 709
Saturday. Sunday.
(Submitted draft---to be post on arXiv if/after accepted)
The timescale of low-mass proto-helium white dwarf evolution
Istrate, Tauris, Langer, Antoniadis
A large number of low-mass (<0.20 Msun) He WDs have recently been discovered. The majority of these are orbiting another WD or a millisecond pulsar (MSP) in a close binary system; a few examples are found to show pulsations or to have a main sequence star companion. There appears to be discrepancies between current theoretical modeling of such low-mass He WDs and a number of key observed cases, indicating that their formation scenario remains to be fully understood. Investigate the formation of detached proto-He WDs in close-orbit low-mass X-ray binaries (LMXBs). The prime focus is to examine the thermal evolution and the contraction phase towards the WD cooling track and investigate how this evolution depends on the WD mass. Calculations are then compared to the most recent observational data. Numerical calculations with a detailed stellar evolution code were used to trace the mass-transfer phase in a large number of close-orbit LMXBs with different initial values of donor star mass, neutron star mass, orbital period and strength of magnetic braking. Subsequently, follow the evolution of the detached low-mass proto-He WDs, including stages with residual shell hydrogen burning and vigorous flashes caused by unstable CNO burning. Find that the time between Roche-lobe detachment until the low-mass proto-He WD reaches the WD cooling track is typically Delta t_proto = 0.5-2 Gyr, depending systematically on the WD mass and therefore on its luminosity. The minimum WD mass for developing shell flashes is ~0.21 Msun for progenitor stars of mass M_2<1.5 Msun (and ~0.18 Msun for M_2=1.6 Msun) [why is shell flash important?]. The long timescale of low-mass proto-He WD evolution can explain a number of recent observations, including some MSP systems hosting He WD companions with very small surface gravities and high effective temperatures. Find no evidence for Delta t_proto to depend on the occurrence of flashes and thus question the suggested dichotomy in thermal evolution of proto-WDs.
(Submitted draft---to be post on arXiv if/after accepted)
The formation of low-mass helium white dwarfs orbiting pulsars: Evolution of low-mass X-ray binaries below the bifurcation period
Istrate, Tauris, Langer
Millisecond pulsars (MSPs) are generally believed to be old neutron stars (NSs) which have been spun up to high rotation rates via accretion of matter from a companion star in a LMXB. This scenario has been strongly supported by various pieces of observational evidence. However, many details of this recycling scenario remain to be understood. Investigate binary evolution in close LMXBs to sturdy the formation of radio MSPs with low-mass He WD companions in tight binaries with orbital periods P_orb=2-9 hr. In particular, examine i) if such observed systems can be reproduced from theoretical modeling using standard prescriptions of orbital angular momentum losses (i.e. with respect to the nature and the strength of magnetic breaking), ii) if the computations of the Roche-lobe detachments can match the observed orbital periods, and iii) if the correlation between WD mass and orbital period (M_WD, P_orb) is valid for systems with P_orb<2days. Numercial calculations with a detailed stellar evolution code were used to trace the mass-transfer phase in ~400 close LMXB systems with different initial values of donor star mass, NS mass, orbital period and the so-called gamma-index of magnetic breaking. Subsequently, follow the orbital and the interior evolution of the detached low-mass (proto) HE WDs, including stages with residual shell H burning. Find that a severe fine-tuning is necessary to reproduce the observed MSPs in tight binaries with He WD companions of mass <0.20 Msun, which suggests that something needs to be modified or is missing in the standard input physics of LMXB modeling. Results from previous independent studies support this conclusion. Demonstrate that the theoretically calculated (M_WD, P_orb)-relation is in general also valid for systems with P_orb<2days, although with a large scatter in He WD masses between 0.15-0.20 Msun. The results of the thermal evolution of the (proto) He WDs are reported in a follow-up paper (Paper II).
(Submitted draft---to be post on arXiv if/after accepted)
The timescale of low-mass proto-helium white dwarf evolution
Istrate, Tauris, Langer, Antoniadis
A large number of low-mass (<0.20 Msun) He WDs have recently been discovered. The majority of these are orbiting another WD or a millisecond pulsar (MSP) in a close binary system; a few examples are found to show pulsations or to have a main sequence star companion. There appears to be discrepancies between current theoretical modeling of such low-mass He WDs and a number of key observed cases, indicating that their formation scenario remains to be fully understood. Investigate the formation of detached proto-He WDs in close-orbit low-mass X-ray binaries (LMXBs). The prime focus is to examine the thermal evolution and the contraction phase towards the WD cooling track and investigate how this evolution depends on the WD mass. Calculations are then compared to the most recent observational data. Numerical calculations with a detailed stellar evolution code were used to trace the mass-transfer phase in a large number of close-orbit LMXBs with different initial values of donor star mass, neutron star mass, orbital period and strength of magnetic braking. Subsequently, follow the evolution of the detached low-mass proto-He WDs, including stages with residual shell hydrogen burning and vigorous flashes caused by unstable CNO burning. Find that the time between Roche-lobe detachment until the low-mass proto-He WD reaches the WD cooling track is typically Delta t_proto = 0.5-2 Gyr, depending systematically on the WD mass and therefore on its luminosity. The minimum WD mass for developing shell flashes is ~0.21 Msun for progenitor stars of mass M_2<1.5 Msun (and ~0.18 Msun for M_2=1.6 Msun) [why is shell flash important?]. The long timescale of low-mass proto-He WD evolution can explain a number of recent observations, including some MSP systems hosting He WD companions with very small surface gravities and high effective temperatures. Find no evidence for Delta t_proto to depend on the occurrence of flashes and thus question the suggested dichotomy in thermal evolution of proto-WDs.
(Submitted draft---to be post on arXiv if/after accepted)
The formation of low-mass helium white dwarfs orbiting pulsars: Evolution of low-mass X-ray binaries below the bifurcation period
Istrate, Tauris, Langer
Millisecond pulsars (MSPs) are generally believed to be old neutron stars (NSs) which have been spun up to high rotation rates via accretion of matter from a companion star in a LMXB. This scenario has been strongly supported by various pieces of observational evidence. However, many details of this recycling scenario remain to be understood. Investigate binary evolution in close LMXBs to sturdy the formation of radio MSPs with low-mass He WD companions in tight binaries with orbital periods P_orb=2-9 hr. In particular, examine i) if such observed systems can be reproduced from theoretical modeling using standard prescriptions of orbital angular momentum losses (i.e. with respect to the nature and the strength of magnetic breaking), ii) if the computations of the Roche-lobe detachments can match the observed orbital periods, and iii) if the correlation between WD mass and orbital period (M_WD, P_orb) is valid for systems with P_orb<2days. Numercial calculations with a detailed stellar evolution code were used to trace the mass-transfer phase in ~400 close LMXB systems with different initial values of donor star mass, NS mass, orbital period and the so-called gamma-index of magnetic breaking. Subsequently, follow the orbital and the interior evolution of the detached low-mass (proto) HE WDs, including stages with residual shell H burning. Find that a severe fine-tuning is necessary to reproduce the observed MSPs in tight binaries with He WD companions of mass <0.20 Msun, which suggests that something needs to be modified or is missing in the standard input physics of LMXB modeling. Results from previous independent studies support this conclusion. Demonstrate that the theoretically calculated (M_WD, P_orb)-relation is in general also valid for systems with P_orb<2days, although with a large scatter in He WD masses between 0.15-0.20 Msun. The results of the thermal evolution of the (proto) He WDs are reported in a follow-up paper (Paper II).
Thursday, July 24, 2014
Day 708
Friday.
Nature
Velocity anti-correlation of diametrically opposed galaxy satellites in the low-redshift Universe
Ibata, et al
In the local universe (z<0.05), pairs of satellite galaxies diametrically opposed and within 150 kpc form the galactic center show aniti-correlation in their velocities at high sigma. Also, the distribution of galaxies in the larger-scale (out to distances of about 2 Mpc) is strongly clumped along the axis joining they inner satellite pair (>7 sigma). This may indicate that planes of co-rotating satellites, similar to those seen around Andromeda, are ubiquitous, and their coherent motion suggests that they represent a substantial repository of angular momentum on scales of about 100 kpc.
1407.6363
The odd couple: quasars and black holes
Tremaine
Quasars emit more energy than any other objects in the universe, yet are not much bigger than the solar system. We are almost certain that quasars are powered by giant BHs of up to 10e10 times the mass of the Sun, and that BHs of between 1e6 and 1e10 Msun---dead quasars---are present at the centers of most galaxies. Our own galaxy contains a BH of 4.3e6 Msun. The mass of the central BH appears to be closely related to other properties of its host galaxy, such as the total mass in stars, but the origin of this relation and the role that BHs play in the formation of galaxies are still a mystery.
1407.6370
A correlation between hard gamma-ray sources and cosmic voids along the line of sight
Furniss, Sutter, Primack, Dominiquez
At the 2.4 sigma level. Less suggestive correlation for the Fermi hard source population (1.7 sigma). The preference for under dense sight lines is not displayed by gamma-ray emitting galaxies within the second Fermi catalog, containing sources detected above 100 MeV, or the SDSS DR7 quasar catalog. Investigate wether this marginal correlation might be a result of lower extragalactic background light photon density within the under dense regions and find that, even in the most extreme case of a entirely under dense sight line, the EBL photon density is only 2% less than the nominal EBL density. This translates into gamma-ray attention of <10%, unable to account for the apparent hard source correlation with under dense LoS.
Nature
Velocity anti-correlation of diametrically opposed galaxy satellites in the low-redshift Universe
Ibata, et al
In the local universe (z<0.05), pairs of satellite galaxies diametrically opposed and within 150 kpc form the galactic center show aniti-correlation in their velocities at high sigma. Also, the distribution of galaxies in the larger-scale (out to distances of about 2 Mpc) is strongly clumped along the axis joining they inner satellite pair (>7 sigma). This may indicate that planes of co-rotating satellites, similar to those seen around Andromeda, are ubiquitous, and their coherent motion suggests that they represent a substantial repository of angular momentum on scales of about 100 kpc.
1407.6363
The odd couple: quasars and black holes
Tremaine
Quasars emit more energy than any other objects in the universe, yet are not much bigger than the solar system. We are almost certain that quasars are powered by giant BHs of up to 10e10 times the mass of the Sun, and that BHs of between 1e6 and 1e10 Msun---dead quasars---are present at the centers of most galaxies. Our own galaxy contains a BH of 4.3e6 Msun. The mass of the central BH appears to be closely related to other properties of its host galaxy, such as the total mass in stars, but the origin of this relation and the role that BHs play in the formation of galaxies are still a mystery.
1407.6370
A correlation between hard gamma-ray sources and cosmic voids along the line of sight
Furniss, Sutter, Primack, Dominiquez
At the 2.4 sigma level. Less suggestive correlation for the Fermi hard source population (1.7 sigma). The preference for under dense sight lines is not displayed by gamma-ray emitting galaxies within the second Fermi catalog, containing sources detected above 100 MeV, or the SDSS DR7 quasar catalog. Investigate wether this marginal correlation might be a result of lower extragalactic background light photon density within the under dense regions and find that, even in the most extreme case of a entirely under dense sight line, the EBL photon density is only 2% less than the nominal EBL density. This translates into gamma-ray attention of <10%, unable to account for the apparent hard source correlation with under dense LoS.
Wednesday, July 23, 2014
Day 707
Thursday.
1407.5633
The stellar initial mass function of early type galaxies from low to high stellar velocity dispersion: homogeneous analysis of ATLAS$^{\rm 3D}$ and Sloan Lens ACS galaxies
Posacki, ... Treu, et al
Study the shape of the IMF of ETGs based on joint lensing and dynamical analysis, and on stellar population synthesis models, for a sample of 55 lens ETGs identified by SLACS. Construct axisymmetric dynamical models based on the Jeans equations which allow for orbital anisotropy and include a DM halo. The models reproduce in detail the observed HST photometry and are constrained by the total projected mass within the Einstein radius and the stellar velocity dispersion (sigma) within the SDSS fibers. Comparing the dynamically-derived stellar (M/L)_dyn to the stellar population ones (M/L)_pop, derived from full-spectrum fitting and assuming a Salpeter IMF, infer the mass normalization of the IMF. Results confirm the previous analysis by the SLACS team that the mass normalization of the IMF of high sigma galaxies is consistent on average with a Salpeter slope. This study allows for a fully consistent study of the trend between IMF and sigma for both the SLACS and ATLAS-3D samples, which explore quite different sigma ranges. The two samples are highly complementary, the first being essentially sigma selected, and the latter volume-limited and nearly mass selected. Find that the two samples merge smoothly into a single trend of the form log alpha = 0.38 * log(sigma_i/200 km/s) - 0.06, where alpha = (M/L)_dyn/(M/L)_pop and sigma_e is the luminosity averaged sigma within one effective radius R_e. This is consistent with a systematic variation of the IMF normalization from Kroupa to Salpeter in the interval sigma_e ~ 90-270 km/s.
1407.5994
Colour matters: the effects of lensing on the positional offsets between optical and submillimetre galaxies in Herschel-ATLAS
Bourne, et al
Report an unexpected variation in the positional offset distributions between Herschel-ATLAS submm sources and their optical associations, depending on both 250 um S/N and 250/350 um color. Show that redder and brighter submm sources have optical associations with a broader distribution of positional offsets than would be expected if these offsets were due to random positional errors in the source extraction. The observation can be explained by two possible effects: either red submm sources trace a more clusters population than blue ones, and their positional errors are increased by confusion; or red submm sources are generally at higher redshifts and are frequently associated with low-z lensing structures which are identified as false counterparts. Perform various analysis of the data, including the multiplicity of optical associations, the z and magnitude distributions in H-ATLAS in comparison to HerMES, and simulations of WL, and conclude that the effects are most likely to be explained by widespread WL of Herschel-SPIRE sources by FG structures. This has important consequences for counterpart identification and derived z-distributions and luminosity functions of submm surveys.
1407.6004
A new method to calibrate the stellar color/surface-brigthness relation
Gould
Show that the standard microlensing technique to measure the angular radius of star using color/surface-brightness relations can be inverted, via late-time proper motion measurements, to calibrate these relations. The method is especially useful for very metal-rich stars because such stars are in short supply in the solar neighborhood where other methods are most effective, but very abundant in Galactic bulge microlensing fields. Provide a list of eight spectroscopically identified high-metllicity bulge stars with the requisite finite-source effects, seven of which will be suitable calibrators when the Giant Magellan Telescope comes on line. Many more such sources can be extracted from current and future microlensing surveys.
1407.6006
The mass dependence of dwarf satellite galaxy quenching
Slater, Bell
Combine observations of LG with data from NASA-Sloan Atlas to show the variation in the quenched fraction of satellite galaxies from low mass dwarf sphperoidals and dwarf irregulars to more massive dwarfs similar to the Magellanic clouds. While almost all of the low mass (M*<1e7 Msun) dwarfs are quenched, at higher masses the quenched fraction decreases to approximately 40-50%. This change in the quenched fraction is large, and suggests a sudden change in the effectiveness of quenching that correlates with satellite mass. Combine this observation with models of satellite infall and ram pressure stripping to show that the low mass satellites must quench within 1-2 Gyr of pericenter passage to maintain a high quenched fraction, but a that many more massive dwarfs must continue to form stars today even though they likely fell in to their host >5 Gyr ago. Also characterize how the susceptibility of dwarfs to ram pressure must vary as a function of mass if it is to account for the change in quenched fractions. Though neither model predicts the quenching effectiveness a priori, this modeling illustrates the physical requirements that the observed quenched fractions place on possible quenching mechanisms.
1407.6068
The SAMI galaxy survey: Early Data Release
Allen, et al
Early data release of Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy survey. Ongoing, IFS survey of ~3400 z<0.12 galaxies, covering GAMA survey regions and a sample of galaxies in clusters. EDR makes public 107 galaxies from GAMA region. Assess the quality of the pipeline used to reduce the data, giving metrics that quantify its performance at all stages. Sky subtraction residuals of 0.9-1.2%, relative flux calibration of 4.1% (sys) + 4.3% (stat), and atmospheric dispersion removed with accuracy of 0."09, < a fifth of a spaxel.
1407.5633
The stellar initial mass function of early type galaxies from low to high stellar velocity dispersion: homogeneous analysis of ATLAS$^{\rm 3D}$ and Sloan Lens ACS galaxies
Posacki, ... Treu, et al
Study the shape of the IMF of ETGs based on joint lensing and dynamical analysis, and on stellar population synthesis models, for a sample of 55 lens ETGs identified by SLACS. Construct axisymmetric dynamical models based on the Jeans equations which allow for orbital anisotropy and include a DM halo. The models reproduce in detail the observed HST photometry and are constrained by the total projected mass within the Einstein radius and the stellar velocity dispersion (sigma) within the SDSS fibers. Comparing the dynamically-derived stellar (M/L)_dyn to the stellar population ones (M/L)_pop, derived from full-spectrum fitting and assuming a Salpeter IMF, infer the mass normalization of the IMF. Results confirm the previous analysis by the SLACS team that the mass normalization of the IMF of high sigma galaxies is consistent on average with a Salpeter slope. This study allows for a fully consistent study of the trend between IMF and sigma for both the SLACS and ATLAS-3D samples, which explore quite different sigma ranges. The two samples are highly complementary, the first being essentially sigma selected, and the latter volume-limited and nearly mass selected. Find that the two samples merge smoothly into a single trend of the form log alpha = 0.38 * log(sigma_i/200 km/s) - 0.06, where alpha = (M/L)_dyn/(M/L)_pop and sigma_e is the luminosity averaged sigma within one effective radius R_e. This is consistent with a systematic variation of the IMF normalization from Kroupa to Salpeter in the interval sigma_e ~ 90-270 km/s.
1407.5994
Colour matters: the effects of lensing on the positional offsets between optical and submillimetre galaxies in Herschel-ATLAS
Bourne, et al
Report an unexpected variation in the positional offset distributions between Herschel-ATLAS submm sources and their optical associations, depending on both 250 um S/N and 250/350 um color. Show that redder and brighter submm sources have optical associations with a broader distribution of positional offsets than would be expected if these offsets were due to random positional errors in the source extraction. The observation can be explained by two possible effects: either red submm sources trace a more clusters population than blue ones, and their positional errors are increased by confusion; or red submm sources are generally at higher redshifts and are frequently associated with low-z lensing structures which are identified as false counterparts. Perform various analysis of the data, including the multiplicity of optical associations, the z and magnitude distributions in H-ATLAS in comparison to HerMES, and simulations of WL, and conclude that the effects are most likely to be explained by widespread WL of Herschel-SPIRE sources by FG structures. This has important consequences for counterpart identification and derived z-distributions and luminosity functions of submm surveys.
1407.6004
A new method to calibrate the stellar color/surface-brigthness relation
Gould
Show that the standard microlensing technique to measure the angular radius of star using color/surface-brightness relations can be inverted, via late-time proper motion measurements, to calibrate these relations. The method is especially useful for very metal-rich stars because such stars are in short supply in the solar neighborhood where other methods are most effective, but very abundant in Galactic bulge microlensing fields. Provide a list of eight spectroscopically identified high-metllicity bulge stars with the requisite finite-source effects, seven of which will be suitable calibrators when the Giant Magellan Telescope comes on line. Many more such sources can be extracted from current and future microlensing surveys.
1407.6006
The mass dependence of dwarf satellite galaxy quenching
Slater, Bell
Combine observations of LG with data from NASA-Sloan Atlas to show the variation in the quenched fraction of satellite galaxies from low mass dwarf sphperoidals and dwarf irregulars to more massive dwarfs similar to the Magellanic clouds. While almost all of the low mass (M*<1e7 Msun) dwarfs are quenched, at higher masses the quenched fraction decreases to approximately 40-50%. This change in the quenched fraction is large, and suggests a sudden change in the effectiveness of quenching that correlates with satellite mass. Combine this observation with models of satellite infall and ram pressure stripping to show that the low mass satellites must quench within 1-2 Gyr of pericenter passage to maintain a high quenched fraction, but a that many more massive dwarfs must continue to form stars today even though they likely fell in to their host >5 Gyr ago. Also characterize how the susceptibility of dwarfs to ram pressure must vary as a function of mass if it is to account for the change in quenched fractions. Though neither model predicts the quenching effectiveness a priori, this modeling illustrates the physical requirements that the observed quenched fractions place on possible quenching mechanisms.
1407.6068
The SAMI galaxy survey: Early Data Release
Allen, et al
Early data release of Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy survey. Ongoing, IFS survey of ~3400 z<0.12 galaxies, covering GAMA survey regions and a sample of galaxies in clusters. EDR makes public 107 galaxies from GAMA region. Assess the quality of the pipeline used to reduce the data, giving metrics that quantify its performance at all stages. Sky subtraction residuals of 0.9-1.2%, relative flux calibration of 4.1% (sys) + 4.3% (stat), and atmospheric dispersion removed with accuracy of 0."09, < a fifth of a spaxel.
Day 706
Wednesday.
1407.5619
The starfish diagram: visualizing data within the context of survey samples
Konstantopoulos
A novel but simple plot that simultaneously visualizes the properties of the sample and the individual: a 'starfish diagram'. The utility and versatility of the plot is demonstrated through its application to astrophysical data and sports statistics. Provide a brief description of the concept and the source code.
1407.5622
Constraints on core collapse from the black hole mass function
Kochanek
Model the observed BH MF under the assumption that BH formation is controlled by the compactness of the stellar core at the time of collapse. Low compactness stars are more likely to explode as supernovae and produce neutron stars, while high compactness stars are more likely to be failed SNe that produce BHs with the mass of the He core of the star. From 3 stellar model sequences and marginalizing over a model of completeness of the BH MF, find that the compactness xi(2.5) above which 50% of core collapses produce BHs is xi(2.5)=0.24 (0.15<xi(2.5)<0.37 at 90% confidence). While models with a sharp transition between successful and failed explosions are always the most likely, the width of the transition between the minimum compactness for BH formation and the compactness above which all core collapses produce BHs is not well constrained. The models also predict that f=0.18 (0.09<f<0.39) of core collapses fail assuming a minimum mass for core collapse of 8Msun. Tested 4 other criteria for BH formation based on xi(2.0) and xi(3.0), the compactnesses at enclosed masses of 2.0 or 3.0 rather than 2.5 Msun, the mass of the Fe core, and the mass inside the O burning shell. Find that xi(2.0) works as well as xi(2.5), while the compactness xi(3.0) works significantly worse, as does using the Fe core mass or the mass enclosed by the O burning shell. As expected from the high compactness of 20-25 Msun stars, BH formation in this mass range provides a natural explanation of the red supergiant problem [what is the RSG problem?].
1407.5623
Mapping the integrated Sachs-Wolfe effect
Manzotti, Dodelson
Present a likelihood technique for extracting the ISW signal from measurements of CMB, galaxy distribution, and maps of gravitational lensing.
1407.5627
Surface photometry of BCGs and intracluster stars in Lambda-CDM
Cooper, Gao, Guo, Frenk, Jenkins, Springel, White
SB profiles of BCGs (from simulations) match well to observations. On average, stars formed in galaxies accreted by the BCG account of ~90% of its total mass, remainder formed in situ. In circular BCG-centered apertures, the superposition of multiple debris clouds (each ~10% of the total BCG mass) from different progenitors can result in an extensive outer diffuse component, qualitatively similar to a 'cD envelope'. These clouds typically originate from tidal stripping at z<1 and comprise both streams and the extended envelopes of other massive galaxies in the cluster. The faint regions of the BCG contribute a significant part of the total cluster stellar mass budget: in the central 1Mpc^2 of a z~0.15 cluster imaged at SDSS-like resolution, the fiducial model predicts 80-95% of M* below a SB of mu_V=26.5 mag arcsec^-2 is associated with accreted stars in the envelope of the BCG. The ratio of BCG stellar mass to total cluster stellar mass is ~30%.
1407.5686
The distortion of the cosmic microwave background by the Milky Way
Czaja, Bromley
MW acting as a large-scale weak gravitational lens of the CMB. Study this effect using a photon ray-tracing code and galactic mass distribution with disk, bulge and halo components. For an observer at the Sun's coordinates in the Galaxy, the bending of CMB photon paths is limited to less than 1 arc second, and only for rays that pass within a few degrees of the Galactic Center. However, the entire sky is affected, resulting in global distortions of the CMB on large angular scales. These distortions can cause the low-order multipoles of a spherical harmonic expansion of the CMB sky temperature to leak into higher-order modes. Thus the component of the CMB dipole that results from the Local Group's motion relative to the local cosmic frame of rest contributes to higher-order moments for an observer in the solar system. With the ray-tracing code, show that the phenomenon is not sensitive to the specific choice of Galactic potential. Also quantitatively rule it out as a contributor to CMB anomalies such as power asymmetry or correlated alignment of low-order multipole moments.
1407.5928
BICEP3: a 95 GHz refracting telescope for degree-scale CMB polarization
Ahmed et al
BICEP3 is a 550mm-aperture refracting telescope for polarimetry of radiation in the CMB at 95 GHz. Similar to BICEP1 and 2, it possesses sufficient resolution to search for signatures of the inflation-induced cosmic gravitational-wave background while utilizing a compact design for ease of construction and to facilitate the characterization and mitigation of systematics. However, BICEP3 represents a significant breakthrough in per-reciever sensitivity, with a focal plane area 5x larger than a BICEP2/Keck array receiver and faster optics. Large-aperture IR-reflective metal-mesh filters and IR-absorptive cold alumina filters and lenses were developed and implemented for its optics. The camera consists of 1280 dual-polarization pixels; each is a pair of orthogonal antenna arrays coupled to transition-edge sensor bolometers and read out by multiplexed SQUIDs. Upon deployment at the SP during the 2014-15 season, BICEP3 will have survey speed comparable to Keck Array 150 GHz (2013), and will significantly enhance spectral separation of primordial B-mode power from that of possible galactic dust contamination in the BICEP2 observation patch.
1407.5619
The starfish diagram: visualizing data within the context of survey samples
Konstantopoulos
A novel but simple plot that simultaneously visualizes the properties of the sample and the individual: a 'starfish diagram'. The utility and versatility of the plot is demonstrated through its application to astrophysical data and sports statistics. Provide a brief description of the concept and the source code.
1407.5622
Constraints on core collapse from the black hole mass function
Kochanek
Model the observed BH MF under the assumption that BH formation is controlled by the compactness of the stellar core at the time of collapse. Low compactness stars are more likely to explode as supernovae and produce neutron stars, while high compactness stars are more likely to be failed SNe that produce BHs with the mass of the He core of the star. From 3 stellar model sequences and marginalizing over a model of completeness of the BH MF, find that the compactness xi(2.5) above which 50% of core collapses produce BHs is xi(2.5)=0.24 (0.15<xi(2.5)<0.37 at 90% confidence). While models with a sharp transition between successful and failed explosions are always the most likely, the width of the transition between the minimum compactness for BH formation and the compactness above which all core collapses produce BHs is not well constrained. The models also predict that f=0.18 (0.09<f<0.39) of core collapses fail assuming a minimum mass for core collapse of 8Msun. Tested 4 other criteria for BH formation based on xi(2.0) and xi(3.0), the compactnesses at enclosed masses of 2.0 or 3.0 rather than 2.5 Msun, the mass of the Fe core, and the mass inside the O burning shell. Find that xi(2.0) works as well as xi(2.5), while the compactness xi(3.0) works significantly worse, as does using the Fe core mass or the mass enclosed by the O burning shell. As expected from the high compactness of 20-25 Msun stars, BH formation in this mass range provides a natural explanation of the red supergiant problem [what is the RSG problem?].
1407.5623
Mapping the integrated Sachs-Wolfe effect
Manzotti, Dodelson
Present a likelihood technique for extracting the ISW signal from measurements of CMB, galaxy distribution, and maps of gravitational lensing.
1407.5627
Surface photometry of BCGs and intracluster stars in Lambda-CDM
Cooper, Gao, Guo, Frenk, Jenkins, Springel, White
SB profiles of BCGs (from simulations) match well to observations. On average, stars formed in galaxies accreted by the BCG account of ~90% of its total mass, remainder formed in situ. In circular BCG-centered apertures, the superposition of multiple debris clouds (each ~10% of the total BCG mass) from different progenitors can result in an extensive outer diffuse component, qualitatively similar to a 'cD envelope'. These clouds typically originate from tidal stripping at z<1 and comprise both streams and the extended envelopes of other massive galaxies in the cluster. The faint regions of the BCG contribute a significant part of the total cluster stellar mass budget: in the central 1Mpc^2 of a z~0.15 cluster imaged at SDSS-like resolution, the fiducial model predicts 80-95% of M* below a SB of mu_V=26.5 mag arcsec^-2 is associated with accreted stars in the envelope of the BCG. The ratio of BCG stellar mass to total cluster stellar mass is ~30%.
1407.5686
The distortion of the cosmic microwave background by the Milky Way
Czaja, Bromley
MW acting as a large-scale weak gravitational lens of the CMB. Study this effect using a photon ray-tracing code and galactic mass distribution with disk, bulge and halo components. For an observer at the Sun's coordinates in the Galaxy, the bending of CMB photon paths is limited to less than 1 arc second, and only for rays that pass within a few degrees of the Galactic Center. However, the entire sky is affected, resulting in global distortions of the CMB on large angular scales. These distortions can cause the low-order multipoles of a spherical harmonic expansion of the CMB sky temperature to leak into higher-order modes. Thus the component of the CMB dipole that results from the Local Group's motion relative to the local cosmic frame of rest contributes to higher-order moments for an observer in the solar system. With the ray-tracing code, show that the phenomenon is not sensitive to the specific choice of Galactic potential. Also quantitatively rule it out as a contributor to CMB anomalies such as power asymmetry or correlated alignment of low-order multipole moments.
1407.5928
BICEP3: a 95 GHz refracting telescope for degree-scale CMB polarization
Ahmed et al
BICEP3 is a 550mm-aperture refracting telescope for polarimetry of radiation in the CMB at 95 GHz. Similar to BICEP1 and 2, it possesses sufficient resolution to search for signatures of the inflation-induced cosmic gravitational-wave background while utilizing a compact design for ease of construction and to facilitate the characterization and mitigation of systematics. However, BICEP3 represents a significant breakthrough in per-reciever sensitivity, with a focal plane area 5x larger than a BICEP2/Keck array receiver and faster optics. Large-aperture IR-reflective metal-mesh filters and IR-absorptive cold alumina filters and lenses were developed and implemented for its optics. The camera consists of 1280 dual-polarization pixels; each is a pair of orthogonal antenna arrays coupled to transition-edge sensor bolometers and read out by multiplexed SQUIDs. Upon deployment at the SP during the 2014-15 season, BICEP3 will have survey speed comparable to Keck Array 150 GHz (2013), and will significantly enhance spectral separation of primordial B-mode power from that of possible galactic dust contamination in the BICEP2 observation patch.
Monday, July 21, 2014
Day 705
Tuesday.
1407.4996
Galaxy and Mass Assembly (GAMA): merging galaxies and their properties
De Propis et al
Derive the close pair fractions and volume merger rates as a function of luminosity and morphology for galaxies in the GAMA survey with -23<M(r)<-17 at 0.01<z<0.22. The merger fraction is about 0.015 at all luminosities (assuming 1/2 of pairs merge) and the volume merger rate is about 0.00035 per cubic Mpc per Gyr. Dry mergers (between red or spheroidal galaxies) are uncommon and decrease with decreasing luminosity. Fainter mergers are wet, between blue or disk galaxies. Damp mergers (one of each type) follow the average of dry and wet mergers. In the brighter luminosity bin (-23<M(r)<-20) the merger rate evolution is flat, irrespective of color or morphology. The makeup of the merging population does not change since z=0.2. Major mergers and dry mergers appear comparatively unimportant in the buildup of the red sequence over the past 2 Gyr. Compare the color, morphology, environmental density and degree of activity of galaxies in pairs to those of more isolated objects in the same volume. Galaxies in close pairs tend to be both redder and slightly more spheroid-dominated. This may be due to "harassment" in multiple previous passes prior to the current interaction. Galaxy pairs do not appear to prefer significantly denser environments. There is no evidence of an enhancement in the AGN fraction in pairs, compared to other galaxies in the same volume.
1407.4730
A universal model for halo concentrations
Diemer, Kravtsov
Present a numerical study of DM halo concentrations in LCDM and self-similar cosmologies. Show that the relation between concentration c and peak height nu exhibits the smallest deviations from universality if halo masses are defined wrt the critical density of the universe. These deviations can be explained by the residual dependence of concentration on the local slope of the matter PS n, which affects both the normalization and shape of the c-nu relation. In particular, there is no well-defined floor in the concentration values. Instead, the minimum concentration depends on redshift: at fixed nu, haloes at higher z experience steeper slopes n, and thus have lower minimum concentrations. Show that the concentrations in the simulations can be accurately described by a universal 7-parameter function of only nu and n. This model matches the LCDM results to ~<5% accuracy up to z=6, and matches scale-free Omega_m=1 models to ~<15%. The model also reproduces the low concentration values of Earth-mass haloes at z~30, and thus correctly extrapolates over 16 orders of magnitude in halo mass. The predictions of the model differ significantly from all models previously proposed n the literature at high masses and redshifts. This model is in excellent agreement with recent lensing measurements of cluster concentrations.
1407.5120
Isophotal shapes of early-type galaxies to very faint levels
Chaware, Cannon, Kembhavi, Pandey
Isophotal shapes of early-type galaxies to very faint levels, reaching ~0.1% of the sky brightness. From integrated exposures of 1 to 4 hours in the SDSS riz bands at the Palomar 5m Hale telescope. The shapes of isophotes of early-type galaxies are important as they are correlated with the physical properties of the galaxies and are influenced by galaxy formation processes. In this paper, report on a sample of 132 E and SO galaxies in one LFC field (53 with redshifts). The shapes of early-type galaxies often vary with radius. Derive average values of isophotal shape parameters in 4 different radial bins along the semi-major axis in each galaxy. Obtain empirical fitting formulae for the probability distribution of the isophotal parameters in each bin and investigate for possible correlations with other global properties of the galaxies. The main finding: the isophotal shapes of the inner regions are statistically different from those in the outer regions [how?]. This suggests that the outer and inter parts of early-type galaxies have evolved somewhat independently.
1407.5151
Estimating luminosities and stellar masses of galaxies photometrically without determining redshifts
Hsieh, Yee
Direct estimate of these quantities using training sets, bypassing photometric redshift determination: Direct Empirical Photometric method (DEmP). DEmP applies two techniques to minimize the effects arising from the non-uniform distribution of training-set galaxy redshifts from a flux-limited sample. First, for each input galaxy, fitting is performed using a subset of the training-set galaxies with photometry and colors closest to those of the input galaxy. Second, the training set is artificially resampled to produce a flat distribution in redshift, or other properties (e.g. luminosity). To test the performance of DEmP, use a 4-filter band mock catalog to examine its ability to recover z, L, M*, and L-M* functions. Also compare the results to those from two publicly available template-fitting methods, finding that the DEmP algorithm outperforms both. Find resampling the training set to have uniform z distribution produces the best results not only in photometric redshift, but also in estimating luminosity and stellar mass. The DEmP method is especially powerful in estimating quantities such as NIR luminosities and stellar mass sing only data from a small number of optical bands.
1407.5350
Weak gravitational lensing as a probe of physical properties of substructures in dark matter haloes
Shirasaki
A novel method to select satellite galaxies in outer regions of galaxy groups or clusters using weak gravitational lensing. The method is based on the theoretical expectation that the tangential shear pattern around satellite galaxies would appear with negative values at the offset distance from the center of the main halo. Thus locate the satellite galaxies statistically with a offset distance of several lensing smoothing scales by using the standard reconstruction of surface mass density maps from WL observation. Test the idea using high res cosmo sims. Show that sub haloes separated from the center of the host halo are successfully located even without assuming the position of the center. For a number of such subhaloes, the characteristic mass and the offset length can be also estimated on a statistical basis. Perform a Fisher analysis to show how well upcoming WL surveys can constrain the mass density profile of satellite galaxies. In the case of LSST with a sky coverage of 20k sq deg, the mass of the member galaxies in the outer region of galaxy clusters can be constrained with an accuracy of ~0.1 dex for galaxy clusters with mass of 1e14 Msun/h at z=0.15. Finally, explore the detectability of tidal stripping features for sub haloes having a wide range of masses: 1e10-13 Msun/h.
1407.5453
Constraining primordial non-Gaussianity via multi-tracer technique with Euclid and SKA
Yamauchi, Takahashi, Oguri
Forecast constraints on f_NL with Euclid and a continuum galaxy survey by SKA, and their combination. Derive a general expression for the covariance matrix of the PS estimates of multiple tracers to show how the multi-tracer technique improves constraints on f_NL. Clarify the role of the overlap fraction of multiple tracers and the divisio method of the tracers. The Fisher matrix analysis indicates that stringent constraints of sigma(f_NL)<1 can be obtained even with a single survey, assuming 5 mass bins. When Euclid and SKA phase 1(2) are combined, constraints of f_NL are improved to sigma(f_NL)=0.34(0.31).
1407.4996
Galaxy and Mass Assembly (GAMA): merging galaxies and their properties
De Propis et al
Derive the close pair fractions and volume merger rates as a function of luminosity and morphology for galaxies in the GAMA survey with -23<M(r)<-17 at 0.01<z<0.22. The merger fraction is about 0.015 at all luminosities (assuming 1/2 of pairs merge) and the volume merger rate is about 0.00035 per cubic Mpc per Gyr. Dry mergers (between red or spheroidal galaxies) are uncommon and decrease with decreasing luminosity. Fainter mergers are wet, between blue or disk galaxies. Damp mergers (one of each type) follow the average of dry and wet mergers. In the brighter luminosity bin (-23<M(r)<-20) the merger rate evolution is flat, irrespective of color or morphology. The makeup of the merging population does not change since z=0.2. Major mergers and dry mergers appear comparatively unimportant in the buildup of the red sequence over the past 2 Gyr. Compare the color, morphology, environmental density and degree of activity of galaxies in pairs to those of more isolated objects in the same volume. Galaxies in close pairs tend to be both redder and slightly more spheroid-dominated. This may be due to "harassment" in multiple previous passes prior to the current interaction. Galaxy pairs do not appear to prefer significantly denser environments. There is no evidence of an enhancement in the AGN fraction in pairs, compared to other galaxies in the same volume.
1407.4730
A universal model for halo concentrations
Diemer, Kravtsov
Present a numerical study of DM halo concentrations in LCDM and self-similar cosmologies. Show that the relation between concentration c and peak height nu exhibits the smallest deviations from universality if halo masses are defined wrt the critical density of the universe. These deviations can be explained by the residual dependence of concentration on the local slope of the matter PS n, which affects both the normalization and shape of the c-nu relation. In particular, there is no well-defined floor in the concentration values. Instead, the minimum concentration depends on redshift: at fixed nu, haloes at higher z experience steeper slopes n, and thus have lower minimum concentrations. Show that the concentrations in the simulations can be accurately described by a universal 7-parameter function of only nu and n. This model matches the LCDM results to ~<5% accuracy up to z=6, and matches scale-free Omega_m=1 models to ~<15%. The model also reproduces the low concentration values of Earth-mass haloes at z~30, and thus correctly extrapolates over 16 orders of magnitude in halo mass. The predictions of the model differ significantly from all models previously proposed n the literature at high masses and redshifts. This model is in excellent agreement with recent lensing measurements of cluster concentrations.
1407.5120
Isophotal shapes of early-type galaxies to very faint levels
Chaware, Cannon, Kembhavi, Pandey
Isophotal shapes of early-type galaxies to very faint levels, reaching ~0.1% of the sky brightness. From integrated exposures of 1 to 4 hours in the SDSS riz bands at the Palomar 5m Hale telescope. The shapes of isophotes of early-type galaxies are important as they are correlated with the physical properties of the galaxies and are influenced by galaxy formation processes. In this paper, report on a sample of 132 E and SO galaxies in one LFC field (53 with redshifts). The shapes of early-type galaxies often vary with radius. Derive average values of isophotal shape parameters in 4 different radial bins along the semi-major axis in each galaxy. Obtain empirical fitting formulae for the probability distribution of the isophotal parameters in each bin and investigate for possible correlations with other global properties of the galaxies. The main finding: the isophotal shapes of the inner regions are statistically different from those in the outer regions [how?]. This suggests that the outer and inter parts of early-type galaxies have evolved somewhat independently.
1407.5151
Estimating luminosities and stellar masses of galaxies photometrically without determining redshifts
Hsieh, Yee
Direct estimate of these quantities using training sets, bypassing photometric redshift determination: Direct Empirical Photometric method (DEmP). DEmP applies two techniques to minimize the effects arising from the non-uniform distribution of training-set galaxy redshifts from a flux-limited sample. First, for each input galaxy, fitting is performed using a subset of the training-set galaxies with photometry and colors closest to those of the input galaxy. Second, the training set is artificially resampled to produce a flat distribution in redshift, or other properties (e.g. luminosity). To test the performance of DEmP, use a 4-filter band mock catalog to examine its ability to recover z, L, M*, and L-M* functions. Also compare the results to those from two publicly available template-fitting methods, finding that the DEmP algorithm outperforms both. Find resampling the training set to have uniform z distribution produces the best results not only in photometric redshift, but also in estimating luminosity and stellar mass. The DEmP method is especially powerful in estimating quantities such as NIR luminosities and stellar mass sing only data from a small number of optical bands.
1407.5350
Weak gravitational lensing as a probe of physical properties of substructures in dark matter haloes
Shirasaki
A novel method to select satellite galaxies in outer regions of galaxy groups or clusters using weak gravitational lensing. The method is based on the theoretical expectation that the tangential shear pattern around satellite galaxies would appear with negative values at the offset distance from the center of the main halo. Thus locate the satellite galaxies statistically with a offset distance of several lensing smoothing scales by using the standard reconstruction of surface mass density maps from WL observation. Test the idea using high res cosmo sims. Show that sub haloes separated from the center of the host halo are successfully located even without assuming the position of the center. For a number of such subhaloes, the characteristic mass and the offset length can be also estimated on a statistical basis. Perform a Fisher analysis to show how well upcoming WL surveys can constrain the mass density profile of satellite galaxies. In the case of LSST with a sky coverage of 20k sq deg, the mass of the member galaxies in the outer region of galaxy clusters can be constrained with an accuracy of ~0.1 dex for galaxy clusters with mass of 1e14 Msun/h at z=0.15. Finally, explore the detectability of tidal stripping features for sub haloes having a wide range of masses: 1e10-13 Msun/h.
1407.5453
Constraining primordial non-Gaussianity via multi-tracer technique with Euclid and SKA
Yamauchi, Takahashi, Oguri
Forecast constraints on f_NL with Euclid and a continuum galaxy survey by SKA, and their combination. Derive a general expression for the covariance matrix of the PS estimates of multiple tracers to show how the multi-tracer technique improves constraints on f_NL. Clarify the role of the overlap fraction of multiple tracers and the divisio method of the tracers. The Fisher matrix analysis indicates that stringent constraints of sigma(f_NL)<1 can be obtained even with a single survey, assuming 5 mass bins. When Euclid and SKA phase 1(2) are combined, constraints of f_NL are improved to sigma(f_NL)=0.34(0.31).
Sunday, July 20, 2014
Day 704
Monday.
1407.4811
Velocity bias from the small scale clustering of SDSS-III BOSS galaxies
Guo, Zheng, Zehavi, Dawson, Skibba, Tinker, Weinberg, White, Schneider
Present the measurements and molding of the projected z-space clustering of CMASS galaxies in the SDSS-III BOSS DR11. For a volume-limited LRG sample in 0.48<z<0.55, perform HOD molding of the small- and intermediate-scale (0.1-60 Mpc/h) projected and z-space 2PCF, with an accurate model built on high resolution N-body simulations. To interpret the measured z-space distortions, the distribution of galaxy velocities must differ from that of the DM inside haloes of ~1e13-14 Msun/h, i.e., the data require the existence of galaxy velocity bias. Most notably, central galaxies on average are not at rest wrt the core of their host haloes (defined by the inner 25% of particles around the halo potential minimum), but rather move around it with a 1d velocity dispersion of 0.22 pm0.03 times that of the DM, implying a spatial offset from the center at the level of <1% of the halo virial radius. The luminous satellite galaxies move more slowly than the DM, with velocities 0.86pm0.08 times those of DM, which suggests that the velocity and spatial distributions of these satellites cannot both be unbiased. The constraints mainly arise from the FoG effect at NL scales and the smoothing to the Kaiser effect in the translinear regime; the robustness of the results is demonstrated by a variety of tests. In addition, no clear evidence is found for a strong luminosity dependence of the velocity bias. Discuss the implications of the existence of galaxy velocity bias for investigations of galaxy formation and cosmology.
1407.4813
Intrinsic alignments of group and cluster galaxies in photometric surveys
Chisari, Mandelbaum, Strauss, Huff, Bahcall
IA have been shown to contaminate WL observable on linear scales, r>10 Mpc/h, but studies of alignments in the NL regime have thus far been inconclusive. Present an estimator for extracting the IA signal of galaxies around stacked clusters of galaxies from multi band imaging data. The estimator removes the contamination caused by galaxies that are gravitationally lensed by the clusters and scattered in z-space due to photometric redshift uncertainties. It uses posterior probability distributions for the redshifts of the galaxies in the sample and it is easily extended to obtain the WL signal while removing the IA contamination. Apply this algorithm to groups and clusters of galaxies identified in SDSS Stripe 82 coadded imaging data over 150 sq deg. Find that the IA signal around stacked clusters in 0.1<z<0.4 is consistent with zero. In terms of the tidal alignment model of Catelan+2001, set joint constraints on the strength of the alignment and the bias of the lensing groups and clusters on scales between 0.1 and 10 Mpc/h, b_L * C_l * rho_crit = -2e-4 pm 14e-4. This constrains the contamination fraction of alignment to lensing signal to the range between [-18,23] % below scales of 1 Mpc/h at 95% CL, and this result depends on the photometric redshift quality and selection criteria used to identify background galaxies. Results are robust to the choice of photometric band in which the shapes are measured (i and r) and to centering on the BCG or on the geometrical center of the clusters.
1407.4811
Velocity bias from the small scale clustering of SDSS-III BOSS galaxies
Guo, Zheng, Zehavi, Dawson, Skibba, Tinker, Weinberg, White, Schneider
Present the measurements and molding of the projected z-space clustering of CMASS galaxies in the SDSS-III BOSS DR11. For a volume-limited LRG sample in 0.48<z<0.55, perform HOD molding of the small- and intermediate-scale (0.1-60 Mpc/h) projected and z-space 2PCF, with an accurate model built on high resolution N-body simulations. To interpret the measured z-space distortions, the distribution of galaxy velocities must differ from that of the DM inside haloes of ~1e13-14 Msun/h, i.e., the data require the existence of galaxy velocity bias. Most notably, central galaxies on average are not at rest wrt the core of their host haloes (defined by the inner 25% of particles around the halo potential minimum), but rather move around it with a 1d velocity dispersion of 0.22 pm0.03 times that of the DM, implying a spatial offset from the center at the level of <1% of the halo virial radius. The luminous satellite galaxies move more slowly than the DM, with velocities 0.86pm0.08 times those of DM, which suggests that the velocity and spatial distributions of these satellites cannot both be unbiased. The constraints mainly arise from the FoG effect at NL scales and the smoothing to the Kaiser effect in the translinear regime; the robustness of the results is demonstrated by a variety of tests. In addition, no clear evidence is found for a strong luminosity dependence of the velocity bias. Discuss the implications of the existence of galaxy velocity bias for investigations of galaxy formation and cosmology.
1407.4813
Intrinsic alignments of group and cluster galaxies in photometric surveys
Chisari, Mandelbaum, Strauss, Huff, Bahcall
IA have been shown to contaminate WL observable on linear scales, r>10 Mpc/h, but studies of alignments in the NL regime have thus far been inconclusive. Present an estimator for extracting the IA signal of galaxies around stacked clusters of galaxies from multi band imaging data. The estimator removes the contamination caused by galaxies that are gravitationally lensed by the clusters and scattered in z-space due to photometric redshift uncertainties. It uses posterior probability distributions for the redshifts of the galaxies in the sample and it is easily extended to obtain the WL signal while removing the IA contamination. Apply this algorithm to groups and clusters of galaxies identified in SDSS Stripe 82 coadded imaging data over 150 sq deg. Find that the IA signal around stacked clusters in 0.1<z<0.4 is consistent with zero. In terms of the tidal alignment model of Catelan+2001, set joint constraints on the strength of the alignment and the bias of the lensing groups and clusters on scales between 0.1 and 10 Mpc/h, b_L * C_l * rho_crit = -2e-4 pm 14e-4. This constrains the contamination fraction of alignment to lensing signal to the range between [-18,23] % below scales of 1 Mpc/h at 95% CL, and this result depends on the photometric redshift quality and selection criteria used to identify background galaxies. Results are robust to the choice of photometric band in which the shapes are measured (i and r) and to centering on the BCG or on the geometrical center of the clusters.
Day 703
Saturday. Sunday.
Annual Review of Astronomy and Astrophysics 2014
The Evolution of Galaxy Structure Over Cosmic Time
Conselice
A comprehensive review of the evolution of galaxy structure in the Universe from z~6 to the local Universe. Detailed pedagogical review of the major methods used to study galaxies morphologically and structurally, including the well-established visual methods for morphology; Sérsic fitting to measure galaxy sizes and surface brightness profile shapes; and non-parameteric structural methods (Concentration, Asymmetry, Clumpiness (CAS) method, Gini/M_20 parameters, and new structural indices). These structural indices measure fundamental properties of galaxies, such as their scale, SFR, and ongoing merger activity. Extensive observational results demonstrate how broad galaxy morphologies and structures change with time up to z~3, from small, compact and peculiar systems in the distant Universe to the formation of the Hubble sequence, dominated by spirals and ellipticals. Structural methods accurately identify galaxies in mergers and allow measurements of the merger history out to z~3. Depict properties and evolution of internal structures of galaxies, such as bulges, disks, bars, and at z>1 large SF clumps. Describe the structure and morphologies of host galaxies of AGN and starbursts/submillimeter galaxies, along with how morphological galaxy quenching occurs. The role of environment in producing structural changes in galaxies over cosmic time is also discussed. Galaxy sizes can also change with time, with measured sizes up to a factor of 2-5 smaller at high z at a given stellar mass. Conclude with a discussion of how the evolving trends, in sizes, structures, and morphologies, reveal the formation mechanisms behind galaxies and provides a new and unique way to test theories of galaxy formation.
Annual Review of Astronomy and Astrophysics 2014
The Evolution of Galaxy Structure Over Cosmic Time
Conselice
A comprehensive review of the evolution of galaxy structure in the Universe from z~6 to the local Universe. Detailed pedagogical review of the major methods used to study galaxies morphologically and structurally, including the well-established visual methods for morphology; Sérsic fitting to measure galaxy sizes and surface brightness profile shapes; and non-parameteric structural methods (Concentration, Asymmetry, Clumpiness (CAS) method, Gini/M_20 parameters, and new structural indices). These structural indices measure fundamental properties of galaxies, such as their scale, SFR, and ongoing merger activity. Extensive observational results demonstrate how broad galaxy morphologies and structures change with time up to z~3, from small, compact and peculiar systems in the distant Universe to the formation of the Hubble sequence, dominated by spirals and ellipticals. Structural methods accurately identify galaxies in mergers and allow measurements of the merger history out to z~3. Depict properties and evolution of internal structures of galaxies, such as bulges, disks, bars, and at z>1 large SF clumps. Describe the structure and morphologies of host galaxies of AGN and starbursts/submillimeter galaxies, along with how morphological galaxy quenching occurs. The role of environment in producing structural changes in galaxies over cosmic time is also discussed. Galaxy sizes can also change with time, with measured sizes up to a factor of 2-5 smaller at high z at a given stellar mass. Conclude with a discussion of how the evolving trends, in sizes, structures, and morphologies, reveal the formation mechanisms behind galaxies and provides a new and unique way to test theories of galaxy formation.
Friday, July 18, 2014
Day 702
Friday.
1407.4516
Weighting the Giants IV: cosmology and neutrino mass
Mantz, von der Linden, Allen, Applegate, ... et al
Employ robust WL measurements to improve constraints from measurements of the galaxy cluster mass function and its evolution, using X-ray selected clusters detected in the ROSAT All-Sky Survey. Lensing analysis provides a constraint on the absolute mass scale of such clusters at the 8% level (including both statistical and systematic uncertainties), a factor of ~2 improvement over the best previous work. In combination with the survey data and extensive X-ray follow-up observations, the WL measurements lead to a tight constraint on a combination of the mean matter density and late-time normalization of the matter PS, sigma_8(Omega_m/0.3)^0.17=0.81pm0.03, with marginalized, 1d constraints of Omega_m=0.26pm0.03 and sigma_8=0.83pm0.04. These constraints are consisted with own previous work, but are offset from some independent cluster studies. New results are in good agreement with constraints from CMB data under the assumption of flat LCDM cosmology with minimal neutrino mass. Consequently, find no evidence for non-minimal neutrino mass from the combination of cluster data with CMB, SN and BAO measurements, regardless of whether WMAP or Planck data are used (and independent of the recent claimed detection of B-modes on degree scales). Also present improved constraints on models of DE (both constant and evolving) and modifications of gravity, for which the cluster measurements provide some of the tightest and most robust constraints to date, as well as primordial non-Gaussianity. In all cases, find results consistent with the standard model of cosmology. Assuming flatness, the constraints for a constant DE EoS from the cluster data alone are at the 15% level.
1407.4563
Electron-capture supernovae exploding within their progenitor wind
Moriya, Tominaga, Langer, Nomoto, Blinnikov, Sorokina
The most massive stars on the AGB, so called super-AGB stars, are thought to produce SNe triggered by electron captures in their degenerate O+Ne+Mg cores. Super-AGB stars are expected to have slow winds with high mass-loss rates, so their wind density is high. The explosions of super-AGB stars are therefore presumed to occur in this dense wind. Provide the first synthetic light curves (LCs) for such events by exploding realistic electron-capture supernova (ecSN) progenitors within their super-AGB winds. Find that the early LC, i.e., before the recombination wave reaches the bottom of the H-rich envelope of SN eject (the plateau phase), is not affected by the dense wind. However, after the plateau phase, the luminosity remains higher with the super-AGB wind is taken into account. Compare results to the historical LC of AN 1054, the progenitor of the Crab Nebula, and show that the explosion of an ecSN within an ordinary super-AGB wind can explain the LC features. Conclude that SN 1054 could have been a Type IIn SN without any extra extreme mass loss which was previously suggested to be necessary to account for its early high luminosity. Also show that the LCs match Type IIn SNe with an early plateau phase ('Type IIn-P') and suggest that they are ecSNe within super-AGB winds. Although some ecSNe can be bright in the optical spectral range due to the large progenitor radius, their X-ray luminosity from the interaction does not necessarily get as bright as other Type IIn SNe whose optical luminosities are also powered by the interaction. Thus, suggest that optically-bright X-ray-faint Type IIn SNe can emerge from ecSNe. Optically-faint Type IIn SNe, such as SN 2008S, can also originate from ecSNe if their H-rich envelope masses are small. Some of them can be observed as 'Type IIn-b' SNe due to the small H-rich envelope mass.
1407.4693
A cluster finding algorithm based on the multi-band identification of red-sequence galaxies
Oguri
Present a new algorithm, CAMIRA, to identify clusters of galaxies in wide-field imaging survey data. Based the algorithm on the stellar population synthesis model to predict colors of red-sequence galaxies at a given redshift for an arbitrary set of bandpass filters, with additional calibration using a sample of spectroscopic galaxies to improve the accuracy of the model prediction. Run the algorithm on ~11960 deg^2 of imaging data from SDSS DR8 to construct a catalog of 71743 clusters in 0.1<z<0.6 with richness after correcting for he incompleteness of the richness estimate greater than 20. Cross-match the cluster catalogue with external cluster catalogues to find that the photometric cluster redshift estimates are accurate with low bias and scatter, and that the corrected richness correlates well with X-ray luminosities and temperatures. Use the CFHTLenS shear catalog to calibrate the mass-richness relation from stacked WL analysis. Stacked WL signals are detected significantly for 8 subsamples of the SDSS clusters divided by redshift and richness binds, which are then compared with model predictions including miscentering effects to constraint mean halo masses of individual bins. Find the richness correlates well with the halo mass, such that the corrected richness limit of 20 corresponds to the cluster virial mass limit of about 1e14 Msun/h for the SDSS DR8 cluster sample.
1407.4516
Weighting the Giants IV: cosmology and neutrino mass
Mantz, von der Linden, Allen, Applegate, ... et al
Employ robust WL measurements to improve constraints from measurements of the galaxy cluster mass function and its evolution, using X-ray selected clusters detected in the ROSAT All-Sky Survey. Lensing analysis provides a constraint on the absolute mass scale of such clusters at the 8% level (including both statistical and systematic uncertainties), a factor of ~2 improvement over the best previous work. In combination with the survey data and extensive X-ray follow-up observations, the WL measurements lead to a tight constraint on a combination of the mean matter density and late-time normalization of the matter PS, sigma_8(Omega_m/0.3)^0.17=0.81pm0.03, with marginalized, 1d constraints of Omega_m=0.26pm0.03 and sigma_8=0.83pm0.04. These constraints are consisted with own previous work, but are offset from some independent cluster studies. New results are in good agreement with constraints from CMB data under the assumption of flat LCDM cosmology with minimal neutrino mass. Consequently, find no evidence for non-minimal neutrino mass from the combination of cluster data with CMB, SN and BAO measurements, regardless of whether WMAP or Planck data are used (and independent of the recent claimed detection of B-modes on degree scales). Also present improved constraints on models of DE (both constant and evolving) and modifications of gravity, for which the cluster measurements provide some of the tightest and most robust constraints to date, as well as primordial non-Gaussianity. In all cases, find results consistent with the standard model of cosmology. Assuming flatness, the constraints for a constant DE EoS from the cluster data alone are at the 15% level.
1407.4563
Electron-capture supernovae exploding within their progenitor wind
Moriya, Tominaga, Langer, Nomoto, Blinnikov, Sorokina
The most massive stars on the AGB, so called super-AGB stars, are thought to produce SNe triggered by electron captures in their degenerate O+Ne+Mg cores. Super-AGB stars are expected to have slow winds with high mass-loss rates, so their wind density is high. The explosions of super-AGB stars are therefore presumed to occur in this dense wind. Provide the first synthetic light curves (LCs) for such events by exploding realistic electron-capture supernova (ecSN) progenitors within their super-AGB winds. Find that the early LC, i.e., before the recombination wave reaches the bottom of the H-rich envelope of SN eject (the plateau phase), is not affected by the dense wind. However, after the plateau phase, the luminosity remains higher with the super-AGB wind is taken into account. Compare results to the historical LC of AN 1054, the progenitor of the Crab Nebula, and show that the explosion of an ecSN within an ordinary super-AGB wind can explain the LC features. Conclude that SN 1054 could have been a Type IIn SN without any extra extreme mass loss which was previously suggested to be necessary to account for its early high luminosity. Also show that the LCs match Type IIn SNe with an early plateau phase ('Type IIn-P') and suggest that they are ecSNe within super-AGB winds. Although some ecSNe can be bright in the optical spectral range due to the large progenitor radius, their X-ray luminosity from the interaction does not necessarily get as bright as other Type IIn SNe whose optical luminosities are also powered by the interaction. Thus, suggest that optically-bright X-ray-faint Type IIn SNe can emerge from ecSNe. Optically-faint Type IIn SNe, such as SN 2008S, can also originate from ecSNe if their H-rich envelope masses are small. Some of them can be observed as 'Type IIn-b' SNe due to the small H-rich envelope mass.
1407.4693
A cluster finding algorithm based on the multi-band identification of red-sequence galaxies
Oguri
Present a new algorithm, CAMIRA, to identify clusters of galaxies in wide-field imaging survey data. Based the algorithm on the stellar population synthesis model to predict colors of red-sequence galaxies at a given redshift for an arbitrary set of bandpass filters, with additional calibration using a sample of spectroscopic galaxies to improve the accuracy of the model prediction. Run the algorithm on ~11960 deg^2 of imaging data from SDSS DR8 to construct a catalog of 71743 clusters in 0.1<z<0.6 with richness after correcting for he incompleteness of the richness estimate greater than 20. Cross-match the cluster catalogue with external cluster catalogues to find that the photometric cluster redshift estimates are accurate with low bias and scatter, and that the corrected richness correlates well with X-ray luminosities and temperatures. Use the CFHTLenS shear catalog to calibrate the mass-richness relation from stacked WL analysis. Stacked WL signals are detected significantly for 8 subsamples of the SDSS clusters divided by redshift and richness binds, which are then compared with model predictions including miscentering effects to constraint mean halo masses of individual bins. Find the richness correlates well with the halo mass, such that the corrected richness limit of 20 corresponds to the cluster virial mass limit of about 1e14 Msun/h for the SDSS DR8 cluster sample.
Wednesday, July 16, 2014
Day 701
Thursday.
1407.4118
Machine lingering classification of SDSS transient survey images
du Buisson et al
Show that multiple machine learning algorithms can match human performance in classifying transient imaging data from the SDSS SN survey into real objects and artifacts. This is the first step in any transient science pipeline and is currently still done by humans, but future surveys such as LSST will necessitate fully machine-enabled solutions. Using features trained from eigenimage analysis (PCA) of single-epoch g, r, i-difference images reaches a completeness (recall) of 95%, while only incorrectly classifying 18% of artifacts as real objects, corresponding to a precision (purity) of 85%. In general the k-nearest neighbor and the SkyNet ANN algorithms performed most robustly compared to other methods such as naive Bayes and kernel SVM. Results show that PCA-based machine learning can match human success levels and can naturally be extended by including multiple epochs of data, transient colors and host galaxy information which should allow for significant further improvements, especially at low signal to noise.
1407.4161
Simulation of a method to directly image exoplanets around multiple stars systems
Thomas, Belikov, Bendek
Direct imaging of extra-solar planets with specialized ground-based instruments (e.g. GPI) will allow detection of planets 1e7 times fainter than their host star. For space-based missions (e.g. WFIRST-AFTA), different teams have shown in laboratories contrasts reaching 1e-10 within a few diffraction limits from the star using a combination of a coronagraph to suppress light coming from the host star and wavefront control system. These demonstrations use a deformable mirror (DM) to remove residual starlight (speckles) created by the imperfections of telescope. However, all these current and future systems focus on detecting faint planets around a single host star or unresolved binaries/multiples, while several targets or planet candidates are located around nearby binary stars such as Alpha Centauri. Until now, it has been thought that removing the light of a companion star is impossible with the current technology, excluding binary star systems from target lists of direct imaging missions. Direct imaging around binaries or multiples systems at a level of contrast allowing Earth-like planets detection is challenging because the region of interest, where a dark zone is essential, is contaminated by the light coming from the host star's companion. Propose a method to simultaneously correct aberrations and diffraction of light coming from the target star. This method works even if the companion star is outside the control region of the DM (beyond its half-Nyquiest frequency), by taking advantage of aliasing effects.
1407.4233
Geometry of star-forming galaxies from SDSS, 3D-HST and CANDELS
van der Wel, ... van Dokkum, Franx, ... et al
Determine the intrinsic, 3d shape distribution of SF galaxies at 0<z<2.5, as inferred from their observed projected axis rations. In the present-day universe, SF galaxies of all masses 1e9-11 Msun are predominantly thin, nearly oblate disks, in line with previous studies. Now extend this to higher redshifts, and find that among massive galaxies (M*>1e10 Msun) disks are the most common geometric shape at all z<2. Lower-mass galaxies at z>1 possess a broad range of geometric shapes: the fraction of elongated (prolate) galaxies increases toward higher redshifts and lower masses. Galaxies with stellar mass 1e9 Msun (1e10 Msun) are a mix of roughly equal numbers of elongated and disk galaxies at z~1 (z~2). This suggests that galaxies in this mass range do not yet have disks that are sustained over many orbital periods, implying that galaxies with present-day stellar mass comparable to that of the MW typically first formed such sustained stellar disks at z~1.5-2. Combined with constraints on the evolution of the SFR density and the distribution of SF over galaxies with different masses, the findings imply that, averaged over cosmic time, the majority of stars formed in disks.
1407.4301
Baryons, Neutrinos, Feedback and Weak gravitational lensing
Harnois-Déraps, van Waerbeke, Viola, Heymans
The effect of baryonic feedback on the DM mass distribution is generally considered to be a nuisance to WL. Measurements of cosmological parameters are affected as feedback alters the cosmic shear signal on angular scales smaller than a few arc minutes. Recent progress on the numerical modeling of baryon physics has shown that this effect could be so large that, rather than being a nuisance, the effect can be constrained with current WL surveys, hence providing an alternative astrophysical insight on one of the most challenging questions of galaxy formation. In order to perform the analysis, construct an analytic fitting formula that describes the effect of the baryons on the mass PS. This fitting formula is based on 3 scenarios of the OWL hydrodynamical simulations. It is specifically calibrated for z<1.5, where it models the simulations to an accuracy that is better than 2% for scales k<10 h/Mpc and better tan 5% for 10<k<100 h/Mpc. Equipped with this precise tool, this paper present the first constraint on baryonic feedback models using gravitational lensing data, from the CFHTLenS. In this analysis, show that the effect of neutrino mass on the mass PS is degenerate with the baryonic feedback at small angular scales and cannot be ignored. Assuming a cosmology precision fixed by WMAP9, find that a universe with no baryon feedback and massless neutrinos is rejected by the CFHTLenS lensing data with 96% confidence. Study shows that ongoing WL surveys (KiDS, HSC and DES) will offer a unique opportunity to probe the physics of baryons at galactic scales, in addition to the expected constraints on the total neutrino mass.
1407.4354
The Galactic Center cloud G2 and its gas streamer
Pfuhl, et al
Detect preceding and lagging gas trails of G2. G1 preceded G2 by 13 years in the same orbit; G2 may be a bright knot in a much more extensive gas streamer. Imaging by SINFONI@VLT integral field spectroscopy.
1407.4118
Machine lingering classification of SDSS transient survey images
du Buisson et al
Show that multiple machine learning algorithms can match human performance in classifying transient imaging data from the SDSS SN survey into real objects and artifacts. This is the first step in any transient science pipeline and is currently still done by humans, but future surveys such as LSST will necessitate fully machine-enabled solutions. Using features trained from eigenimage analysis (PCA) of single-epoch g, r, i-difference images reaches a completeness (recall) of 95%, while only incorrectly classifying 18% of artifacts as real objects, corresponding to a precision (purity) of 85%. In general the k-nearest neighbor and the SkyNet ANN algorithms performed most robustly compared to other methods such as naive Bayes and kernel SVM. Results show that PCA-based machine learning can match human success levels and can naturally be extended by including multiple epochs of data, transient colors and host galaxy information which should allow for significant further improvements, especially at low signal to noise.
1407.4161
Simulation of a method to directly image exoplanets around multiple stars systems
Thomas, Belikov, Bendek
Direct imaging of extra-solar planets with specialized ground-based instruments (e.g. GPI) will allow detection of planets 1e7 times fainter than their host star. For space-based missions (e.g. WFIRST-AFTA), different teams have shown in laboratories contrasts reaching 1e-10 within a few diffraction limits from the star using a combination of a coronagraph to suppress light coming from the host star and wavefront control system. These demonstrations use a deformable mirror (DM) to remove residual starlight (speckles) created by the imperfections of telescope. However, all these current and future systems focus on detecting faint planets around a single host star or unresolved binaries/multiples, while several targets or planet candidates are located around nearby binary stars such as Alpha Centauri. Until now, it has been thought that removing the light of a companion star is impossible with the current technology, excluding binary star systems from target lists of direct imaging missions. Direct imaging around binaries or multiples systems at a level of contrast allowing Earth-like planets detection is challenging because the region of interest, where a dark zone is essential, is contaminated by the light coming from the host star's companion. Propose a method to simultaneously correct aberrations and diffraction of light coming from the target star. This method works even if the companion star is outside the control region of the DM (beyond its half-Nyquiest frequency), by taking advantage of aliasing effects.
1407.4233
Geometry of star-forming galaxies from SDSS, 3D-HST and CANDELS
van der Wel, ... van Dokkum, Franx, ... et al
Determine the intrinsic, 3d shape distribution of SF galaxies at 0<z<2.5, as inferred from their observed projected axis rations. In the present-day universe, SF galaxies of all masses 1e9-11 Msun are predominantly thin, nearly oblate disks, in line with previous studies. Now extend this to higher redshifts, and find that among massive galaxies (M*>1e10 Msun) disks are the most common geometric shape at all z<2. Lower-mass galaxies at z>1 possess a broad range of geometric shapes: the fraction of elongated (prolate) galaxies increases toward higher redshifts and lower masses. Galaxies with stellar mass 1e9 Msun (1e10 Msun) are a mix of roughly equal numbers of elongated and disk galaxies at z~1 (z~2). This suggests that galaxies in this mass range do not yet have disks that are sustained over many orbital periods, implying that galaxies with present-day stellar mass comparable to that of the MW typically first formed such sustained stellar disks at z~1.5-2. Combined with constraints on the evolution of the SFR density and the distribution of SF over galaxies with different masses, the findings imply that, averaged over cosmic time, the majority of stars formed in disks.
1407.4301
Baryons, Neutrinos, Feedback and Weak gravitational lensing
Harnois-Déraps, van Waerbeke, Viola, Heymans
The effect of baryonic feedback on the DM mass distribution is generally considered to be a nuisance to WL. Measurements of cosmological parameters are affected as feedback alters the cosmic shear signal on angular scales smaller than a few arc minutes. Recent progress on the numerical modeling of baryon physics has shown that this effect could be so large that, rather than being a nuisance, the effect can be constrained with current WL surveys, hence providing an alternative astrophysical insight on one of the most challenging questions of galaxy formation. In order to perform the analysis, construct an analytic fitting formula that describes the effect of the baryons on the mass PS. This fitting formula is based on 3 scenarios of the OWL hydrodynamical simulations. It is specifically calibrated for z<1.5, where it models the simulations to an accuracy that is better than 2% for scales k<10 h/Mpc and better tan 5% for 10<k<100 h/Mpc. Equipped with this precise tool, this paper present the first constraint on baryonic feedback models using gravitational lensing data, from the CFHTLenS. In this analysis, show that the effect of neutrino mass on the mass PS is degenerate with the baryonic feedback at small angular scales and cannot be ignored. Assuming a cosmology precision fixed by WMAP9, find that a universe with no baryon feedback and massless neutrinos is rejected by the CFHTLenS lensing data with 96% confidence. Study shows that ongoing WL surveys (KiDS, HSC and DES) will offer a unique opportunity to probe the physics of baryons at galactic scales, in addition to the expected constraints on the total neutrino mass.
1407.4354
The Galactic Center cloud G2 and its gas streamer
Pfuhl, et al
Detect preceding and lagging gas trails of G2. G1 preceded G2 by 13 years in the same orbit; G2 may be a bright knot in a much more extensive gas streamer. Imaging by SINFONI@VLT integral field spectroscopy.
Tuesday, July 15, 2014
Day 700
Wednesday.
1407.1906
Building unbiased estimators from non-Gaussian likelihoods with application to shear estimation
Madhavacheril, McDonald, Sehgal, Slosar
Develop a general framework for generating estimators of a given quantity which are unbiased to a given order in the difference between the true value of the underlying quantity and the fiducial position in theory space around which the likelihood is expanded. Apply this formalism to reserve the optimal quadratic estimator and show how the replacement of the second derivative matrix with the Fisher matrix is generic way of creating an unbiased estimator (if one does not modify the initial guess at the weight matrix C^{-1} iteratively based estimates from the data, which generally creates a bias). Next, apply the approach to estimation of shear lensing, closely following the work of B+A (2014). The first order estimator reduces to their estimator in the limit of zero shear, but it also naturally allows for the case of non-constant shear and the easy calculation of correlation functions of power spectra using standard methods. Both the first order estimator and B+A's estimator exhibit a bias which is quadratic in true shear. The third-order estimator is, at least in the realism of the toy problem of B+A, unbiased to 0.1% in relative shear errors (Delta g)/g for shears up to |g|=0.2.
1407.2584
The Primordial Inflation Polarization Explorer (PIPER)
Lazear, ... Bennett, ... et al
PIPER is a balloon-borne CMB polarimeter designed to search for evidence of inflation by measuring the large-angluar scale CMB polarization signal. BICEP2 recently reported a detection of B-mode plower corresponding to the tensor-t-scalar ratio r=0.2 on ~2 degree scales. If the BICEP2 signal is caused by inflationary gravitational waves (IGWs), then there should be a corresponding increase in B-mode power on angular scales larger than 18 degrees. PIPER is currently the only suborbital instrument capable of fulling testing and extending the BICEP2 results by measuring the B-mode PS on angular calls theta=~0.6deg to 90 deg, covering both the deionization bump and recombination peak, with sensitivity to measure the tensor-to-scalar ratio down to r=0.007, and four frequency bands to distinguish foregrounds. PIPER will accomplish this by mapping 85% of the sky in 4 frequency bands over a series of 8 conventional balloon flights from the northern and southern hemispheres. The instrument has background-limited sensitivity provided by fully cryogenic (1.5K) optics focusing the sky signal onto four 32x40 pixel arrays of time-domain multiplexed Transition-Edge Sensor (TES) bolometers belt ad 140 mK. Polarization sensitivity and systematic control are provided by front-end Variable-delay Polarization Modulators (VPMs), which rapidly modulate only the polarized sky signal at 3 Hz and allow PIPER to instantaneously measure the full Stokes vector (I,Q,U,V) for each pointing. Describe the PIPER instrument and progress towards its first flight.
1407.2600
Dark Sky Simulations: Early data release
Skillmann, ... Wechsler, Holz, ... et al
The Dark Sky Simulations are an ongoing series of cosmological N-body simulations designed to provide a quantitative and accessible model of the evolution of the large-scale universe. Such models are essential, since we lack a sufficiently accurate analytic model of NL gravitational clustering. Made public the simulation of 1e12 (10240^3) particles in (8Gpc/h)^3, performed with 2HOT (purely tree-based adaptive N-body method), running on 200k processors, with data analysis by yt [?]. Provide an overview of the derived halo catalogs, mass function, PS and light cone data. Show self-consistency in the mass function and mass PS at the 1% level over a range of more than 1000 in particle mass. Present a novel method to distribute and access very large datasets, based on an abstraction of the WWW as a file system, remote memory-mapped file access semantics, and a space-filling curve index. This method has been implemented for the data release, and provides a means to not only query stored results such as halo catalogs, but also to design and deploy new analysis techniques on large distributed datasets.
1407.2906
Pre-flight integration and characterization of the SPIDER balloon-borne telescope
Rahlin, et al
Present the results of integration and characterization of the SPIDER instrument after the 2013 pre-flight campaign. SPIDER is a balloon-borne polarimeter designed to probe the primordial gravitational wave signal in the degree-scale B-mode polarization of the CMB. With six independent telescopes housing over 2000 detectors in the 94 GHz and 150 GHz frequency bands, SPIDER will map 7.5% of the sky with a depth of 11 to 14 muK*arcmin at each frequency, which is a factor of ~5 improvement over Planck. Discuss the integration of the pointing, cryogenic, electronics, and power subsystems, as well as pre-flight characterization of the detectors and optical systems. SPIDER is well prepared for a December 2014 flight from Antarctica, and is expected to be limited by astrophysical FG emission, and not instrumental sensitivity, over the survey region.
1407.3787
A 52 hours VLT/FORS2 spectrum of a bright z~7 HUDF galaxy: no Ly-alpha emission
Vanzella et al
52hr integration over the past 5 years of the z~7 candidate in HUDF show no emission line or continuum over the whole wavelength range, up to 10100A. Combine upper limits with SED modeling to refine redshift estimate to z=6.82pm0.1 (1 sigma); SED modeling also indicates dust-corrected SFR of ~20 Msun/yr. A plausible interpretation is that it is moderately evolved and contains sufficient gas and dust to attenuate the Lya emission, before it reaches the IGM. The redshift confirmation or even the best z~7 candidates is very hard to achieve (unless the Lya or unusually strong rest-UV nebular emission lines are present) with the current generation of 8-10m class telescopes. Show that both JWST and E-ELT will be necessary to make decisive progresses. Currently, the increased redshift accuracy obtained with this kind of analysis makes ALMA an interesting option for the redshift confirmation.
1407.3795
Globular clusters and dark satellite galaxies through the stream velocity
Naoz, Narayan
The formation of purely baryonic globular clusters with no gravitationally bound DM is still a theoretical challenge. Show that these objects might form naturally whenever there is a relative stream velocity between baryons and DM. The stream velocity causes a phase shift between linear modes of baryonic and DM perturbations, which translates to a spatial offset between the two components when the collapse. For a 2 (3) sigma density fluctuations, baryonic clumps with masses in the range 1e5 to 2.5e6 Msun (1e5 to 4e6 Msun) collapse outside the virial radii of their counterpart DM haloes. These objects could survive as long-lived DM-free objects and might conceivably become globular clusters. In addition, their DM counterparts, which were deprived of gas, might become dark satellite galaxies.
1407.3955
Dark matter fraction in lens galaxies: new estimates from microlensing
Jiménez-Vicente, Mediavilla, Kochanik, Muñoz
A joint estimate of the stellar/DM mass fraction in lens galaxies and the average size of the accretion disk of lensed quasars from microlensing measurements of 27 quasar image pairs seen though 19 lens galaxies. The maximum likelihood estimate for the fraction of the surface mass density in the form of stars is alpha=0.2pm0.1 near the Einstein radius of the lenses (~1-2 effective radii). The estimate for the average accretion disk size is r_s=6.0 sqrt(M/0.3Msun) light-days. The fraction of mass in stars at these radii is significantly larger than previous estimates from microlensing studies assuming quasars were point-like. The corresponding local DM fraction of 80 is in good agreement with other estimates based on strong lensing or kinematics. The size of the accretion disk inferred in the present study is slightly larger than previous estimates.
1407.4025
Joint astrometric solution of Hipparcos and Gaia: a recipe for the Hundred Thousand Proper Motions project
Michalik, Lindegren, Hobbs, Lammers
First Gaia data expected in 2016; 100k stars in common with Hipparcos. 24 yr difference between the two will allow accurate proper motions. Predict proper motion accuracies between 14 and 145 muas/yr, depending on stellar magnitude and amount of Gaia available. Improvement of proper motion expected with later and more accurate Gaia data.
1407.1906
Building unbiased estimators from non-Gaussian likelihoods with application to shear estimation
Madhavacheril, McDonald, Sehgal, Slosar
Develop a general framework for generating estimators of a given quantity which are unbiased to a given order in the difference between the true value of the underlying quantity and the fiducial position in theory space around which the likelihood is expanded. Apply this formalism to reserve the optimal quadratic estimator and show how the replacement of the second derivative matrix with the Fisher matrix is generic way of creating an unbiased estimator (if one does not modify the initial guess at the weight matrix C^{-1} iteratively based estimates from the data, which generally creates a bias). Next, apply the approach to estimation of shear lensing, closely following the work of B+A (2014). The first order estimator reduces to their estimator in the limit of zero shear, but it also naturally allows for the case of non-constant shear and the easy calculation of correlation functions of power spectra using standard methods. Both the first order estimator and B+A's estimator exhibit a bias which is quadratic in true shear. The third-order estimator is, at least in the realism of the toy problem of B+A, unbiased to 0.1% in relative shear errors (Delta g)/g for shears up to |g|=0.2.
1407.2584
The Primordial Inflation Polarization Explorer (PIPER)
Lazear, ... Bennett, ... et al
PIPER is a balloon-borne CMB polarimeter designed to search for evidence of inflation by measuring the large-angluar scale CMB polarization signal. BICEP2 recently reported a detection of B-mode plower corresponding to the tensor-t-scalar ratio r=0.2 on ~2 degree scales. If the BICEP2 signal is caused by inflationary gravitational waves (IGWs), then there should be a corresponding increase in B-mode power on angular scales larger than 18 degrees. PIPER is currently the only suborbital instrument capable of fulling testing and extending the BICEP2 results by measuring the B-mode PS on angular calls theta=~0.6deg to 90 deg, covering both the deionization bump and recombination peak, with sensitivity to measure the tensor-to-scalar ratio down to r=0.007, and four frequency bands to distinguish foregrounds. PIPER will accomplish this by mapping 85% of the sky in 4 frequency bands over a series of 8 conventional balloon flights from the northern and southern hemispheres. The instrument has background-limited sensitivity provided by fully cryogenic (1.5K) optics focusing the sky signal onto four 32x40 pixel arrays of time-domain multiplexed Transition-Edge Sensor (TES) bolometers belt ad 140 mK. Polarization sensitivity and systematic control are provided by front-end Variable-delay Polarization Modulators (VPMs), which rapidly modulate only the polarized sky signal at 3 Hz and allow PIPER to instantaneously measure the full Stokes vector (I,Q,U,V) for each pointing. Describe the PIPER instrument and progress towards its first flight.
1407.2600
Dark Sky Simulations: Early data release
Skillmann, ... Wechsler, Holz, ... et al
The Dark Sky Simulations are an ongoing series of cosmological N-body simulations designed to provide a quantitative and accessible model of the evolution of the large-scale universe. Such models are essential, since we lack a sufficiently accurate analytic model of NL gravitational clustering. Made public the simulation of 1e12 (10240^3) particles in (8Gpc/h)^3, performed with 2HOT (purely tree-based adaptive N-body method), running on 200k processors, with data analysis by yt [?]. Provide an overview of the derived halo catalogs, mass function, PS and light cone data. Show self-consistency in the mass function and mass PS at the 1% level over a range of more than 1000 in particle mass. Present a novel method to distribute and access very large datasets, based on an abstraction of the WWW as a file system, remote memory-mapped file access semantics, and a space-filling curve index. This method has been implemented for the data release, and provides a means to not only query stored results such as halo catalogs, but also to design and deploy new analysis techniques on large distributed datasets.
1407.2906
Pre-flight integration and characterization of the SPIDER balloon-borne telescope
Rahlin, et al
Present the results of integration and characterization of the SPIDER instrument after the 2013 pre-flight campaign. SPIDER is a balloon-borne polarimeter designed to probe the primordial gravitational wave signal in the degree-scale B-mode polarization of the CMB. With six independent telescopes housing over 2000 detectors in the 94 GHz and 150 GHz frequency bands, SPIDER will map 7.5% of the sky with a depth of 11 to 14 muK*arcmin at each frequency, which is a factor of ~5 improvement over Planck. Discuss the integration of the pointing, cryogenic, electronics, and power subsystems, as well as pre-flight characterization of the detectors and optical systems. SPIDER is well prepared for a December 2014 flight from Antarctica, and is expected to be limited by astrophysical FG emission, and not instrumental sensitivity, over the survey region.
1407.3787
A 52 hours VLT/FORS2 spectrum of a bright z~7 HUDF galaxy: no Ly-alpha emission
Vanzella et al
52hr integration over the past 5 years of the z~7 candidate in HUDF show no emission line or continuum over the whole wavelength range, up to 10100A. Combine upper limits with SED modeling to refine redshift estimate to z=6.82pm0.1 (1 sigma); SED modeling also indicates dust-corrected SFR of ~20 Msun/yr. A plausible interpretation is that it is moderately evolved and contains sufficient gas and dust to attenuate the Lya emission, before it reaches the IGM. The redshift confirmation or even the best z~7 candidates is very hard to achieve (unless the Lya or unusually strong rest-UV nebular emission lines are present) with the current generation of 8-10m class telescopes. Show that both JWST and E-ELT will be necessary to make decisive progresses. Currently, the increased redshift accuracy obtained with this kind of analysis makes ALMA an interesting option for the redshift confirmation.
1407.3795
Globular clusters and dark satellite galaxies through the stream velocity
Naoz, Narayan
The formation of purely baryonic globular clusters with no gravitationally bound DM is still a theoretical challenge. Show that these objects might form naturally whenever there is a relative stream velocity between baryons and DM. The stream velocity causes a phase shift between linear modes of baryonic and DM perturbations, which translates to a spatial offset between the two components when the collapse. For a 2 (3) sigma density fluctuations, baryonic clumps with masses in the range 1e5 to 2.5e6 Msun (1e5 to 4e6 Msun) collapse outside the virial radii of their counterpart DM haloes. These objects could survive as long-lived DM-free objects and might conceivably become globular clusters. In addition, their DM counterparts, which were deprived of gas, might become dark satellite galaxies.
1407.3955
Dark matter fraction in lens galaxies: new estimates from microlensing
Jiménez-Vicente, Mediavilla, Kochanik, Muñoz
A joint estimate of the stellar/DM mass fraction in lens galaxies and the average size of the accretion disk of lensed quasars from microlensing measurements of 27 quasar image pairs seen though 19 lens galaxies. The maximum likelihood estimate for the fraction of the surface mass density in the form of stars is alpha=0.2pm0.1 near the Einstein radius of the lenses (~1-2 effective radii). The estimate for the average accretion disk size is r_s=6.0 sqrt(M/0.3Msun) light-days. The fraction of mass in stars at these radii is significantly larger than previous estimates from microlensing studies assuming quasars were point-like. The corresponding local DM fraction of 80 is in good agreement with other estimates based on strong lensing or kinematics. The size of the accretion disk inferred in the present study is slightly larger than previous estimates.
1407.4025
Joint astrometric solution of Hipparcos and Gaia: a recipe for the Hundred Thousand Proper Motions project
Michalik, Lindegren, Hobbs, Lammers
First Gaia data expected in 2016; 100k stars in common with Hipparcos. 24 yr difference between the two will allow accurate proper motions. Predict proper motion accuracies between 14 and 145 muas/yr, depending on stellar magnitude and amount of Gaia available. Improvement of proper motion expected with later and more accurate Gaia data.
Monday, July 14, 2014
Day 699
Tuesday.
1407.3275
Fermi-LAT gamma-ray anisotropy and intensity explained by unresolved Radio-Loud Active Galactic Nuclei
Di Mauro, et al
Measured properties of the isotropic gamma-ray background (IGRB) can be used to constrain the characteristics of proposed contributing sources. Find that collectively radio-loud AGN can account for the entirety of the IGRB intensity but a negligible contribution to the anisotropy, while high-synchrotron-peaked BL Lacertae objects provide the dominant contribution to the anisotropy. In anticipation of upcoming measurements with the Fermi-LAT and the forthcoming Cherenkov Telescope Array, predict the anisotropy in the broader energy range that will be accessible to future observations.
1407.3276
The mass dependance of satellite quenching in Milky Way-like haloes
Phillips, ... Boylan-Kolchin, Bullock, et al
Examine the quenching of satellite galaxies around isolated MW-like hosts in the local Universe, from SDSS. Find that the efficiency of satellite quenching around isolated galaxies is low and roughly constant over 2 orders of magnitude in satellite stellar mass (M*=1e8.5 to 10.5 Msun), with only ~20% of systems quenched as a result of environmental processes. While largely independent of satellite stellar mass, satellite quenching does exhibit clear dependence on the properties of the host. Show that satellite of passive hosts are substantially more likely to be quenched than those of SF hosts, and present evidence that more massive haloes quench their satellites more efficiently. These results extend trends seen previously in more massive host haloes and for higher satellite masses. Taken together, it appears that galaxies with stellar masses larger than about 1e8 Msun are uniformly resistant to environmental quenching, with the relative harshness of the host environment likely serving as the primary driver of satellite quenching. At lower stellar masses (<1e8 Msun), however, observations of the LG suggest that the vast majority of the satellite galaxies are quenched, potentially pointing towards a characteristic satellite mass scale below which quenching efficiency increases dramatically.
1407.3330
Statistical challenges in weak lensing cosmology
Takada
Address one of the most fundamental, statistical questions inherent in WL cosmology: whether or not we can recover the initial Gaussian information content of LSS by combining the WL observables, here focused on the WL PS and bispectrum. To address this question, fully take into account correlations between the PS of different multipoles and the bispectra of different triangle configurations, measured from a finite area survey. In particular, show that super-survey modes whose length scale is larger than of comparable with the survey size cause significant sample variance n the WL correlations via the mode-coupling with sub-survey modes due to NL gravitational clustering -- the so-called super-sample variance. In this paper, discuss the origin of the super-sample variance and then study the information content inherent in the WL correlation functions up to 3-pt level.
1407.3344
Influence of stellar multiplicity on planet formation. II. Planets are less common in multiple-star systems with separations smaller than 1500 AU
Wang et al
Almost half of stellar systems in the solar neighborhood are made of multiple stars; in multiple-star systems, planet formation is under the dynamical influence of stellar companions, and the planet occurrence rate is expected to be different from that for single stars. Infer the planet occurrence rate in multiple-star systems by measuring the stellar multiplicity rate for planet host stars. for a 56 subsample of Kepler planet host stars, look for stellar companions. Detect 59 visual stellar companions to 25 planet host stars with AO data. After detection bias correction, find that planet formation is supposed in multiple-star systems with separations smaller than 1500 AU.
1407.3275
Fermi-LAT gamma-ray anisotropy and intensity explained by unresolved Radio-Loud Active Galactic Nuclei
Di Mauro, et al
Measured properties of the isotropic gamma-ray background (IGRB) can be used to constrain the characteristics of proposed contributing sources. Find that collectively radio-loud AGN can account for the entirety of the IGRB intensity but a negligible contribution to the anisotropy, while high-synchrotron-peaked BL Lacertae objects provide the dominant contribution to the anisotropy. In anticipation of upcoming measurements with the Fermi-LAT and the forthcoming Cherenkov Telescope Array, predict the anisotropy in the broader energy range that will be accessible to future observations.
1407.3276
The mass dependance of satellite quenching in Milky Way-like haloes
Phillips, ... Boylan-Kolchin, Bullock, et al
Examine the quenching of satellite galaxies around isolated MW-like hosts in the local Universe, from SDSS. Find that the efficiency of satellite quenching around isolated galaxies is low and roughly constant over 2 orders of magnitude in satellite stellar mass (M*=1e8.5 to 10.5 Msun), with only ~20% of systems quenched as a result of environmental processes. While largely independent of satellite stellar mass, satellite quenching does exhibit clear dependence on the properties of the host. Show that satellite of passive hosts are substantially more likely to be quenched than those of SF hosts, and present evidence that more massive haloes quench their satellites more efficiently. These results extend trends seen previously in more massive host haloes and for higher satellite masses. Taken together, it appears that galaxies with stellar masses larger than about 1e8 Msun are uniformly resistant to environmental quenching, with the relative harshness of the host environment likely serving as the primary driver of satellite quenching. At lower stellar masses (<1e8 Msun), however, observations of the LG suggest that the vast majority of the satellite galaxies are quenched, potentially pointing towards a characteristic satellite mass scale below which quenching efficiency increases dramatically.
1407.3330
Statistical challenges in weak lensing cosmology
Takada
Address one of the most fundamental, statistical questions inherent in WL cosmology: whether or not we can recover the initial Gaussian information content of LSS by combining the WL observables, here focused on the WL PS and bispectrum. To address this question, fully take into account correlations between the PS of different multipoles and the bispectra of different triangle configurations, measured from a finite area survey. In particular, show that super-survey modes whose length scale is larger than of comparable with the survey size cause significant sample variance n the WL correlations via the mode-coupling with sub-survey modes due to NL gravitational clustering -- the so-called super-sample variance. In this paper, discuss the origin of the super-sample variance and then study the information content inherent in the WL correlation functions up to 3-pt level.
1407.3344
Influence of stellar multiplicity on planet formation. II. Planets are less common in multiple-star systems with separations smaller than 1500 AU
Wang et al
Almost half of stellar systems in the solar neighborhood are made of multiple stars; in multiple-star systems, planet formation is under the dynamical influence of stellar companions, and the planet occurrence rate is expected to be different from that for single stars. Infer the planet occurrence rate in multiple-star systems by measuring the stellar multiplicity rate for planet host stars. for a 56 subsample of Kepler planet host stars, look for stellar companions. Detect 59 visual stellar companions to 25 planet host stars with AO data. After detection bias correction, find that planet formation is supposed in multiple-star systems with separations smaller than 1500 AU.
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