We study the surface brightness profiles of a sample of brightest cluster galaxies (BCGs) with 0.3 < z < 0.9. The BCGs are selected from the first Red-sequence Cluster Survey and an X-ray cluster survey. The surface brightness profiles of the BCGs are measured using HST ACS images, and the majority of them can be well modeled by a single Sérsic profile with a typical Sérsic index n ∼ 6 and a half-light radius ∼30 kpc. Although the single Sérsic model fits the profiles well, we argue that the systematics in the sky background measurement and the coupling between the model parameters make the comparison of the best-fit model parameters ambiguous. Direct comparison of the BCG profiles, on the other hand, has revealed an inside-out growth for these most massive galaxies: as the mass of a BCG increases, the central mass density of the galaxy increases slowly (ρ 1kpc ∝ M 0.39 * ), while the slope of the outer profile grows continuously shallower (α r 1/4 ∝ M −2.5 * ). Such a fashion of growth continues down to the less massive early-type galaxies (ETGs) as a smooth function of galaxy mass, without apparent distinction between BCGs and non-BCGs. For the very massive ETGs and BCGs, the slope of the Kormendy relation starts to trace the slope of the surface brightness profiles and becomes insensitive to subtle profile evolution. These results are generally consistent with dry mergers being the major driver of the mass growth for BCGs and massive ETGs. We also find strong correlations between the richness of clusters and the properties of BCGs: the more massive the clusters are, the more massive the BCGs (M * bcg ∝ M 0.6 clusters ) and the shallower their surface brightness profiles. After taking into account the bias in the cluster samples, we find the masses of the BCGs have grown by at least a factor of 1.5 from z = 0.5 to z = 0, in contrast to the previous findings of no evolution. Such an evolution validates the expectation from the ΛCDM model.

We present measurements of the specific star formation rate (SSFR)–stellar mass relation for star‐forming galaxies. Our deep spectroscopic samples are based on the Redshift One LDSS3 Emission line Survey (ROLES) and European Southern Observatory (ESO) public spectroscopy at z= 1, and on the Sloan Digital Sky Survey (SDSS) at z= 0.1. These data sets cover an equally deep mass range of 8.5 ≲ log(M*/M⊙) ≲ 11 at both epochs. We find that the SSFR–mass relation evolves in a way which is remarkably independent of stellar mass, as we previously found for the SFR density (SFRD)–mass relation. However, we see a subtle upturn in SSFR–mass for the lowest mass galaxies (which may at least partly be driven by mass‐incompleteness in the K‐selected sample). This upturn is suggestive of greater evolution for lower mass galaxies, which may be explained by less massive galaxies forming their stars later and on longer time‐scales than higher mass galaxies, as implied by the ‘cosmic downsizing’ scenario. Parametrizing the e‐folding time‐scale and formation redshift as simple functions of baryonic mass gives best‐fitting parametrizations of τ(Mb) ∝M−1.01b and 1 +zf(Mb) ∝M0.30b. This subtle upturn is also seen in the SFRD as a function of stellar mass. At higher masses, such as those probed by previous surveys, the evolution in SSFR–mass is almost independent of stellar mass. At higher masses [log(M*/M⊙) > 10] the shapes of the cumulative cosmic SFRDs are very similar at both z= 0.1 and 1.0, both showing 70 per cent of the total SFRD above a mass of log(M*/M⊙) > 10. Mass functions are constructed for star‐forming galaxies and found to evolve by only <35 per cent between z= 1 and 0.1 over the whole mass range. The evolution is such that the mass function decreases with increasing cosmic time, confirming that galaxies are leaving the star‐forming sequence/blue cloud. The observational results are extended to z∼ 2 by adding two recent Lyman break galaxy samples, and data at these three epochs (z= 0.1, 1, 2) are compared with the GALFORM semi‐analytic model of galaxy formation. GALFORM predicts an overall SFRD as a function of stellar mass in reasonable agreement with the observations. The star formation time‐scales inferred from 1/SSFR also give reasonable overall agreement, with the agreement becoming worse at the lowest and highest masses. The models do not reproduce the SSFR upturn seen in our data at low masses, where the effects of extinction and active galactic nuclei feedback should be minimal and the comparison should be most robust.

Using the sample from the Redshift One LDSS-3 Emission line Survey (ROLES), we probe the dependence of star formation rate (SFR) and specific star formation rate (sSFR) as a function of stellar mass M * and environment as defined by local galaxy density, in the Chandra Deep Field South field. Our spectroscopic sample consists of 312 galaxies with K AB < 24, corresponding to stellar mass log(M * /M ) > 8.5, and with [O II] derived SFR > 0.3 M yr −1 , at 0.889 ≤ z ≤ 1.149. The results have been compared directly with the Sloan Digital Sky Survey Stripe 82 sample at 0.032 ≤ z ≤ 0.05. For star-forming galaxies, we confirm that there is little correlation between SFR and density at z ∼ 0. However, for the lowest mass galaxies in our z ∼ 1 sample, those with log(M * /M ) < 10, we find that both the median SFR and sSFR increase significantly with increasing local density. The 'downsizing' trend for lowmass galaxies to be quenched progressively later in time appears to be more pronounced in moderately overdense environments. Overall we find that the evolution of star formation in galaxies is most strongly driven by their stellar mass, with local galaxy density playing a role that becomes increasingly important for lower mass galaxies.

Using wide-field BV R c I imaging for a sample of 16 intermediate redshift (0.17 < z < 0.55) galaxy clusters from the Canadian Network for Observational Cosmology (CNOC1) Survey, we investigate the dependence of cluster galaxy populations and their evolution on environment. Galaxy photometric redshifts are estimated using an empirical photometric redshift technique and galaxy groups are identified using a modified friends-of-friends algorithm in photometric redshift space. We utilize the red galaxy fraction (f red ) to infer the evolutionary status of galaxies in clusters, using both individual galaxies and galaxies in groups. We apply the local galaxy density, Σ 5 , derived using the fifth nearest-neighbor distance, as a measure of local environment, and the clustercentric radius, r CL , as a proxy for global cluster environment. Our cluster sample exhibits a Butcher-Oemler effect in both luminosity-selected and stellar-massselected samples. We find that f red depends strongly on Σ 5 and r CL , and the Butcher-Oemler effect is observed in all Σ 5 and r CL bins. However, when the cluster galaxies are separated into r CL bins, or into group and non-group subsamples, the dependence on local galaxy density becomes much weaker. This suggests that the properties of the dark matter halo in which the galaxy resides

We use a K-selected (22.5 < K AB < 24.0) sample of dwarf galaxies (8.4 < log(M * /M ) < 10) at 0.89 < z < 1.15 in the Chandra Deep Field-South to measure their contribution to the global star formation rate density (SFRD), as inferred from their [O II] flux. By comparing with [O II]-based studies of higher stellar mass galaxies, we robustly measure a turnover in the [O II] luminosity density at a stellar mass of M ∼ 10 10 M . By comparison with the [O II]-based SFRD measured from the Sloan Digital Sky Survey we confirm that, while the SFRD of the lowest mass galaxies changes very little with time, the SFRD of more massive galaxies evolves strongly, such that they dominate the SFRD at z = 1.