The evolution of the galaxy mass assembly and star formation activity from z=1 to z=0 as a function of environment

Aim of this thesis is to investigate the role of the galaxy massand environment in shaping the galaxyproperties, characterising the history of stellar evolution, the stellar massassembly, and the structure development of galaxiesin different environments, by tracing the star formation rate, the total stellar massof galaxiesand the morphology at different redshifts. The data exploited in this thesis come from four surveys which focus on different environments and redshifts in the range z=0 to z=1: the Wide-field Nearby Galaxy-clusterSurvey (WINGS - Fasano et al. 2006), the Padova-Millennium Galaxyand Group catalogue (PM2GC - Calvi, Poggianti, Vulcani 2011), the IMACS Cluster Building Survey (ICBS - Oemler et al. 2012a,b, in preparation), and the ESO Distant Cluster Survey (EDisCS - White et al. 2005). First, analysing a sample of galaxiesfrom EDisCS and using field data from literature, I study the ongoing Star Formation Rate (SFR) and the Specific Star Formation Rate (SSFR) at z=0.4-0.8 for different stellar massesand environments. In mass-limited samples, the SFR at a fixed galaxy massdeclines with time. The SSFR declines as galaxy stellar massincreases, showing that the current star formation contributes more to the fractional growth of low- mass galaxiesthan high- mass galaxies. The median SFR is lower in cluster star-forming galaxiesthan in the field, by a factor of ~1.5. I conclude that the average SFR in star-forming galaxiesvaries with galaxyenvironment at a fixed galaxy mass. Subsequently, using both WINGS and EDisCS data, I examine the morphology- massrelation (the way the proportion of galaxiesof different morphological types changes with galaxy mass), and find it strongly depends on redshift. Both at z=0 and z~0.6, ~40% of the stellar massis in elliptical galaxies. Another ~43% of the massis in S0 galaxiesin local clusters, while it is in late-types in distant clusters. Using data from all the surveys, I then analyse the galaxy stellar massfunction in mass-limited samples, focusing on a number of aspects, such as the role of the global and local environment in shapingthe mass distribution, its evolution in clusters compared to the field, and what simulations predict for galaxieslocated in haloes of different mass. The main results are: (1) at intermediate redshift I do not detect any dependence of the massfunction on the global environment: galaxiesin clusters, groupsand in the field are regulated by similar mass distributions, at least for M_star/M_sun >10.5. (2) In clusters, I investigate the evolution of the total massfunction from z~0.6 to z\sim 0, and I find that in the local Universe there are proportionally more low- mass galaxiesthan at high-z. This evolution is mainly driven by the galaxy massgrowth due to star formation and by morphological transformations from one type to the other. (3) I contrast the evolution of the massfunction in clusters and in the field from z~ 0.4 and z~ 0.6 to z~ 0 and find that it is very similar, hence independent of global environment. (4) I analyse the role of the local galaxydensity in shaping the massfunction, both at low and intermediate redshift, in clusters and in the field. Galaxiesin different local density regions follow different massfunctions. This result, coupled with point (1) above, suggests that galaxyproperties such as galaxy massare not much dependent on halo mass, but do depend on local scale processes. (5) Simulations are able to reproduce the observed massfunction for field galaxiesin the local Universe, while they fail in reproducing clusters at both low- and high-z and the field at high-z, suggesting that the current treatment of star formation performed in simulations has to be improved to well reproduce the galaxy mass distributionat different epochs and in different environments. Having found that both the morphological fractions and the massfunctions vary with redshift, I then study how this evolution influences the ellipticity distributionof cluster early-type galaxies, finding that the variation with redshift is due to a change both of the median and of the shapeof the distributionswith redshift. The evolution of early-type galaxiesis not simply related to the different mass distributionsat high- and low-z, but it is mainly related to the evolution of the morphological mix with redshift and hence to the relative contribution of ellipticals and S0s at the two epochs. Finally, I present the spectroscopic analysis of galaxiesin a field containing a z=0.96 cluster, Cl 1103.7-1245C, as part of the EDisCS project, for which I carried out the data reduction. I characterise the galaxypopulation of the two structures I singled out (the ``main cluster'' and a ``secondary structure'') and I compare my results with the galaxypopulations of the other EDisCS clusters that have comparable values of velocity dispersions, but are located at lower redshifts. In general, the properties of the main cluster are in line with the other clusters and the expected evolution, while the secondary structure is an outstanding system, composed only of low- mass, strongly star-forming and morphologically peculiar galaxies. To conclude, the role of the galaxy stellar massis undisputed in driving galaxyevolution: galaxiesare characterised by a wide range of total stellar massesand the evolution of their properties strongly depends on their mass. Anyway, massand environment are not independent. The environment, besides affecting some galaxyproperties, is partially able to influence the mass distribution: more massive galaxiesare preferentially found at higher densities.