Cosmic Evolution Of Virial And Stellar Mass In Massive Early-Type Galaxies

We measure the average mass properties of a sample of 41 strong gravitational lenses at moderate redshift (z similar to 0.4-0.9) and present the lens redshift for six of these galaxies for the first time. Using the techniques of strong and weak gravitational lensing on archival data obtained from the Hubble Space Telescope, we determine that the average mass overdensity profile of the lenses can be fit with a power-law profile (Delta Sigma proportional to R-0.86 +/- 0.16) that is within 1 sigma of an isothermal profile (Delta Sigma proportional to R-1) with velocity dispersion sigma(upsilon) = 260 +/- 20 km s(-1). Additionally, we use a two-component de Vaucouleurs + Navarro-Frenk-White (NFW) model to disentangle the total mass profile into separate luminous and dark matter components and determine the relative fraction of each component. We measure the average rest frame V-band stellar mass-to-light ratio (gamma(V) = 4.0 +/- 0.6hM(circle dot)/L-circle dot) and virial mass-to-light ratio (tau(V) = 300 +/- 90h M-circle dot/L-circle dot) for our sample, resulting in a virial-to-stellar mass ratio of M-vir/M-* = 75 +/- 25. Relaxing the NFW assumption, we estimate that changing the inner slope of the dark matter profile by similar to 20% yields a similar to 30% change in stellar mass-to-light ratio. Finally, we compare our results to a previous study using low-redshift lenses to understand how galaxy mass profiles evolve over time. We investigate the evolution of M-vir/M-(z) = alpha(1 + z)(beta), and find best-fit parameters of alpha = 51 +/- 36 and beta = 0.9 +/- 1.8, constraining the growth of virial-to-stellar mass ratio over the last similar to 7 Gyr. We note that, by using a sample of strong lenses, we are able to constrain the growth of M-vir/M-(z) without making any assumptions about the initial mass function of the stellar population.

STAGES: the Space Telescope A901/2 Galaxy Evolution Survey

Yifei Guo

We present an overview of the Space Telescope A901/2 Galaxy Evolution Survey (STAGES). STAGES is a multiwavelength project designed to probe physical drivers of galaxy evolution across a wide range of environments and luminosity. A complex multicluster system at z similar to 0.165 has been the subject of an 80-orbit F606W Hubble Space Telescope (HST)/Advanced Camera for Surveys (ACS) mosaic covering the full 0 degrees.5 x 0 degrees.5 (similar to 5 x 5 Mpc(2)) span of the supercluster. Extensive multiwavelength observations with XMM-Newton, GALEX, Spitzer, 2dF, Giant Metrewave Radio Telescope and the 17-band COMBO-17 photometric redshift survey complement the HST imaging. Our survey goals include simultaneously linking galaxy morphology with other observables such as age, star formation rate, nuclear activity and stellar mass. In addition, with the multiwavelength data set and new high-resolution mass maps from gravitational lensing, we are able to disentangle the large-scale structure of the system. By examining all aspects of an environment we will be able to evaluate the relative importance of the dark matter haloes, the local galaxy density and the hot X-ray gas in driving galaxy transformation. This paper describes the HST imaging, data reduction and creation of a master catalogue. We perform the Sersic fitting on the HST images and conduct associated simulations to quantify completeness. In addition, we present the COMBO-17 photometric redshift catalogue and estimates of stellar masses and star formation rates for this field. We define galaxy and cluster sample selection criteria, which will be the basis for forthcoming science analyses, and present a compilation of notable objects in the field. Finally, we describe the further multiwavelength observations and announce public access to the data and catalogues.

Blackwell Publishing Ltd, Oxford2009

Survey of gravitationally-lensed objects in HSC imaging (SuGOHI) III. Statistical strong lensing constraints on the stellar IMF of CMASS galaxies

Hung-Hsu Chan

Context. The determination of the stellar initial mass function (IMF) of massive galaxies is one of the open problems in cosmology. Strong gravitational lensing is one of the few methods that allow us to constrain the IMF outside of the Local Group. Aims. The goal of this study is to statistically constrain the distribution in the IMF mismatch parameter, defined as the ratio between the true stellar mass of a galaxy and that inferred assuming a reference IMF, of massive galaxies from the Baryon Oscillation Spectroscopic Survey (BOSS) constant mass (CMASS) sample. Methods. We took 23 strong lenses drawn from the CMASS sample, measured their Einstein radii and stellar masses using multi-band photometry from the Hyper Suprime-Cam survey, then fitted a model distribution for the IMF mismatch parameter and dark matter halo mass to the whole sample. We used a prior on halo mass from weak lensing measurements and accounted for strong lensing selection effects in our model. Results. Assuming a Navarro Frenk and White density profile for the dark matter distribution, we infer a value mu(IMF) = -0.04 +/- 0.11 for the average base-10 logarithm of the IMF mismatch parameter, defined with respect to a Chabrier IMF. A Salpeter IMF is in tension with our measurements. Conclusions. Our results are consistent with a scenario in which the region of massive galaxies where the IMF normalisation is significantly heavier than that of the Milky Way is much smaller than the scales 5-10 kpc probed by the Einstein radius of the lenses in our sample, as recent spatially-resolved studies of the IMF in massive galaxies suggest.

2019

The GOGREEN survey: Internal dynamics of clusters of galaxies at redshift 0.9-1.4

Hung-Hsu Chan, Pascale Jablonka

Context. The study of galaxy cluster mass profiles (M(r)) provides constraints on the nature of dark matter and on physical processes affecting the mass distribution. The study of galaxy cluster velocity anisotropy profiles (beta (r)) informs the orbits of galaxies in clusters, which are related to their evolution. The combination of mass profiles and velocity anisotropy profiles allows us to determine the pseudo phase-space density profiles (Q(r)); numerical simulations predict that these profiles follow a simple power law in cluster-centric distance.Aims. We determine the mass, velocity anisotropy, and pseudo phase-space density profiles of clusters of galaxies at the highest redshifts investigated in detail to date.Methods. We exploited the combination of the GOGREEN and GCLASS spectroscopic data-sets for 14 clusters with mass M-200 >= 10(14) M-circle dot at redshifts 0.9

EDP SCIENCES S A2021