Modelling of galaxy evolution in groups

Executive Summary

Clusters and groups of galaxies, as representations of the densest regions of the universe, are key environments to understand the evolution of galaxies as traced by their star formation history, intimately related to their morphology and gas content. Indeed it has been reported that the global star formation rates of spiral galaxies located in the innermost regions of nearby and intermediate-redshift clusters appear strongly depressed as compared to the results found for similar galaxies at larger galactocentric radii. Less information is available in the literature with respect to the evolution of the star formation activity of the population of dwarf galaxies in clusters. Metallicity is, with stellar mass, one of the fundamental physical properties of galaxies, reflecting the gas reprocessed by stars and any exchange of gas between the galaxy and its environment. The study of the relation between stellar mass and metallicity is central to our understanding of the physical processes that govern star formation in galaxies. There seems to be a well defined relation between mass and luminosity in the sense that more massive galaxies are also more metal rich. This holds at all redshifts, although for a given stellar mass, more distant galaxies appear less metal rich than local galaxies. Up to now, few works have been devoted to the study of the metal content of cluster star-forming galaxies; some of them show a different behaviour with respect to field galaxies, and this effect has been attributed to the action of the cluster environment.

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Detailed Research

Most galaxies in the recent universe (z generation of substantial amounts of diffuse intragroup light during the formation of compact configurations, and the definition of the morphological fractions. On a more fundamental level, we expect that the results of this investigation will provide additional insight into the connection between the observed properties of galaxies and their groupings and those of the underlying dark matter distribution.

From the theoretical point of view, it is expected that galaxies located in a high density region of a cluster or group can be affected by tidal effects giving rise to a reorganization of their material. In addition the gaseous component of the galaxies may suffer from stripping and/or evaporation as a result of the interaction with the intergalactic medium (IGM). The relative high density of the IGM and the probability of galaxy encounters in rich environments favours the presence of selective losses of material, especially in disks and halos of late type galaxies. In the densest zones, these actions may lead to important phenomena of galaxy evolution and transformation, including structural changes. In clusters, effects like the galaxy "harassment" can introduce such changes in time scales that can be explored with observations. During the last years we have been involved in the development of galaxy computer simulations. Our aim is the study of the evolution of galaxies in groups of galaxies. The initial conditions are obtained by realizations of small systems in a standard Lambda cold dark matter Universe at z~3 and we are characterizing the dynamical aspects of the evolution in time until our epoch, i.e, luminosity function evolution and morphological evolution. Initially galaxies are discs which follow a Schechter luminosity function law.

Scientific objectives

  1. T To perform a large number of simulations with a variety of initial conditions, in order to understand the formation and evolution of groups of galaxies. We expect to be able to predict the fraction of compact groups in the local universe and the distribution function of the amount of light located in the intragroup region in groups of a given mass.