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Register a new userOn the evolution of the central density of quiescent galaxies
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We investigate the origin of the evolution of the population-averaged central stellar mass density ($Sigma_1$) of quiescent galaxies (QGs) by probing the relation between stellar age and $Sigma_1$ at $zsim0$. We use the Zurich ENvironmental Study (ZENS), which is a survey of galaxy groups with a large fraction of satellite galaxies. QGs shape a narrow locus in the $Sigma_1-M_{star}$ plane, which we refer to as $Sigma_1$ ridgeline. Colors of ($B-I$) and ($I-J$) are used to divide QGs into three age categories: young ($<2~mathrm{Gyr}$), intermediate ($2-4~mathrm{Gyr}$), and old ($>4~mathrm{Gyr}$). At fixed stellar mass, old QGs on the $Sigma_1$ ridgeline have higher $Sigma_1$ than young QGs. This shows that galaxies landing on the $Sigma_1$ ridgeline at later epochs arrive with lower $Sigma_1$, which drives the zeropoint of the ridgeline down with time. We compare the present-day zeropoint of the oldest population at $z=0$ with the zeropoint of the quiescent population 4 Gyr back in time, at $z=0.37$. These zeropoints are identical, showing that the intrinsic evolution of individual galaxies after they arrive on the $Sigma_1$ ridgeline must be negligible, or must evolve parallel to the ridgeline during this interval. The observed evolution of the global zeropoint of 0.07 dex over the last 4 Gyr is thus largely due to the continuous addition of newly quenched galaxies with lower $Sigma_1$ at later times (progenitor bias). While these results refer to the satellite-rich ZENS sample as a whole, our work suggests a similar age-$Sigma_1$ trend for central galaxies.
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Massive compact systems at 0.2<z<0.6 are the missing link between the predominantly compact population of massive quiescent galaxies at high redshift and their analogs and relics in the local volume. The evolution in number density of these extreme objects over cosmic time is the crucial constraining factor for the models of massive galaxy assembly. We select a large sample of ~200 intermediate-redshift massive compacts from the BOSS spectroscopic dataset by identifying point-like SDSS photometric sources with spectroscopic signatures of evolved redshifted galaxies. A subset of our targets have publicly available high-resolution ground-based images that we use to augment the dynamical and stellar population properties of these systems by their structural parameters. We confirm that all BOSS compact candidates are as compact as their high-redshift massive counterparts and less than half the size of similarly massive systems at z~0. We use the completeness-corrected numbers of BOSS compacts to compute lower limits on their number densities in narrow redshift bins spanning the range of our sample. The abundance of extremely dense quiescent galaxies at 0.2<z<0.6 is in excellent agreement with the number densities of these systems at high redshift. Our lower limits support the models of massive galaxy assembly through a series of minor mergers over the redshift range 0<z<2.
We discuss the evolution of the interstellar medium of quiescent galaxies, currently emerging from recent analyses, with the help of a simple model based on well-established empirical relations such as the stellar mass functions and the main sequence of star formation. This model is meant to describe observed quantities without making specific assumptions on the nature of quenching processes, but relying on their observable consequences. We find that the high gas fractions seen or suggested at high redshift in quiescent galaxies, and their apparent mild evolution at early times, can be mostly attributed to a progenitor effect where recently quenched galaxies with ~10% gas fractions dominate the quiescent galaxy population until z~1. In the same context, the much lower gas and dust fractions measured in local early-type galaxies are interpreted as the product of the steady depletion of their interstellar medium on a ~2 Gyr timescale, coupled with a higher fraction of more gas-exhaustive events.
We have studied the evolution of high redshift quiescent galaxies over an effective area of ~1.7 deg^2 in the COSMOS field. Galaxies have been divided according to their star-formation activity and the evolution of the different populations has been investigated in detail. We have studied an IRAC (mag_3.6 < 22.0) selected sample of ~18000 galaxies at z > 1.4 with multi-wavelength coverage. We have derived accurate photometric redshifts (sigma=0.06) and other important physical parameters through a SED-fitting procedure. We have divided our sample into actively star-forming, intermediate and quiescent galaxies depending on their specific star formation rate. We have computed the galaxy stellar mass function of the total sample and the different populations at z=1.4-3.0. We have studied the properties of high redshift quiescent galaxies finding that they are old (1-4 Gyr), massive (log(M/M_sun)~10.65), weakly star forming stellar populations with low dust extinction (E(B-V) < 0.15) and small e-folding time scales (tau ~ 0.1-0.3 Gyr). We observe a significant evolution of the quiescent stellar mass function from 2.5 < z < 3.0 to 1.4 < z < 1.6, increasing by ~ 1 dex in this redshift interval. We find that z ~ 1.5 is an epoch of transition of the GSMF. The fraction of star-forming galaxies decreases from 60% to 20% from z ~ 2.5-3.0 to z ~ 1.4-1.6 for log(M/M_sun) > 11, while the quiescent population increases from 10% to 50% at the same redshift and mass intervals. We compare the fraction of quiescent galaxies derived with that predicted by theoretical models and find that the Kitzbichler & White (2007) model is the one that better reproduces the data. Finally, we calculate the stellar mass density of the star-forming and quiescent populations finding that there is already a significant number of quiescent galaxies at z > 2.5 (rho~6.0 MsunMpc^-3).
Using the very deep Subaru images of the GOODS-N region, from the MOIRCS Deep Survey and images from the HST/ACS, we have measured the Luminosity Ratio (LR) of the outer to the central regions of massive (M>10^{10.5}M_{Sun}) galaxies at fixed radii in a single rest-frame for z<3.5 as a new approach to the problem of size evolution. We didnt observe any evolution in the median LR. Had a significant size growth occurred, the outer to central luminosity ratios would have demonstrated a corresponding increase with a decrease in redshift.
We quantify evolution in the cluster scale stellar mass - halo mass (SMHM) relations parameters using 2323 clusters and brightest central galaxies (BCGs) over the redshift range $0.03 le z le 0.60$. The precision on inferred SMHM parameters is improved by including the magnitude gap ($rm m_{gap}$) between the BCG and fourth brightest cluster member (M14) as a third parameter in the SMHM relation. At fixed halo mass, accounting for $rm m_{gap}$, through a stretch parameter, reduces the SMHM relations intrinsic scatter. To explore this redshift range, we use clusters, BCGs, and cluster members identified using the Sloan Digital Sky Survey C4 and redMaPPer cluster catalogs and the Dark Energy Survey redMaPPer catalog. Through this joint analysis, we detect no systematic differences in BCG stellar mass, $rm m_{gap}$, and cluster mass (inferred from richness) between the datsets. We utilize the Pareto function to quantify each parameters evolution. We confirm prior findings of negative evolution in the SMHM relations slope (3.5$sigma$) and detect negative evolution in the stretch parameter (4.0$sigma$) and positive evolution in the offset parameter (5.8$sigma$). This observed evolution, combined with the absence of BCG growth, when stellar mass is measured within 50kpc, suggests that this evolution results from changes in the clusters $rm m_{gap}$. For this to occur, late-term growth must be in the intra-cluster light surrounding the BCG. We also compare the observed results to Illustris TNG 300-1 cosmological hydrodynamic simulations and find modest qualitative agreement. However, the simulations lack the evolutionary features detected in the real data.
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