Incorporating Morphological Types into Semi-analytic Schemes for Galaxy Formation

The last decade of research on elliptical galaxies has produced a wealth of new information concerning both their detailed structure and their global scaling relations. We review the old and new results about isophote shapes and subcomponents (Sect. 1), scaling relations of global parameters and redshift evolution (Sect. 2), and the ages, metallicities (Sect. 3) and abundance ratios (Sect. 4). Finally, we confront the observations with hierarchical formation scenarios of elli...

The decrease, since z=1, of the rest-frame UV luminosity density is related to global changes in morphology, color and emission lines properties of galaxies. This is apparently followed by a similar decrease of the rest-frameIR luminosity density. I discuss the relative contribution from the different galaxy morphological types to the observed evolution. The main contributors are compact galaxies observed in large number at optical wavelengths, and the sparse population of ...

The colour-magnitude relation (CMR) of cluster ellipticals has been widely used to constrain their star formation histories (SFHs) and to discriminate between the monolithic and merger paradigms of elliptical galaxy formation. We investigate the elliptical CMR predicted in the merger paradigm by using a LCDM hierarchical merger model. We first highlight sections of the literature which indicate that the traditional use of fixed apertures to derive colours gives a distorted vi...

In this paper we present new chemo-spectro-photometric models of elliptical galaxies in which infall of primordial gas is allowed to occur. They aim to simulate the collapse of a galaxy made of two components, i.e. luminous material and dark matter. The mass of the dark component is assumed to be constant in time, whereas that of the luminous material is supposed to accrete at a suitable rate. They also include the effect of galactic winds powered by supernova explosions and ...

Using isophotal radius correlations for a sample of 2MASS ellipticals, we have constructed a series of template surface brightness profiles to describe the profile shapes of ellipticals as a function of luminosity. The templates are a smooth function of luminosity, yet are not adequately matched to any fitting function supporting the view that ellipticals are weakly non-homologous with respect to structure. Through comparison to the templates, it is discovered that elliptical...

We present a model for the broad morphological distinction between the disk and spheroidal components of galaxies. Elaborating on the hierarchical clustering scheme of galaxy formation proposed by Cole et al., we assume that galaxies form stars quiescently in a disk until they are disrupted into a spheroidal configuration by mergers. We calculate formation and merging histories, and the evolution in colour, luminosity and morphology of the galaxy populations in different envi...

We address the origin of the `downsizing' of elliptical galaxies, according to which the stars in more massive galaxies formed earlier and over a shorter period than those in less massive galaxies. We show that this could be the natural result of a shutdown of star formation in dark matter haloes above a critical mass of 10^12MSun. This is demonstrated using a semianalytic simulation of galaxy formation within the standard hierarchical scenario of structure formation. The ass...

We model the galaxy formation in a series of high-resolution N-body simulations using the semi-analytical approach. Unlike many earlier investigations based on semi-analytical models, we make use of the subhalos resolved in the $N$-body simulations to follow the mergers of galaxies in dark halos, and we show that this is pivotal in modeling correctly the galaxy luminosity function at the bright end and the bimodal nature of galaxy color distribution. Mergers of galaxies based...

Elliptical and S0 galaxies dominate the galaxy population in nearby rich clusters such as Coma. Studies of the evolution of the colors, M/L ratios, and line indices of early-type galaxies indicate that they have been a highly homogeneous, slowly evolving population over the last ~65% of the age of the Universe. On the other hand, recent evidence suggests that many early-type galaxies in clusters have been transformed from spiral galaxies since z~1. Arguably the most spectacul...

Galaxies have clearly evolved since the universe was 1 Gyr old, but methods to trace and quantify this evolution are still in their infancy. In this paper I demonstrate that with the careful use of a `physical morphology' it is possible to determine quantitatively how the process of galaxy evolution is occurring out to z=4. Using a system of parameters that traces star formation and galaxy interactions, I show how distinct galaxy populations at high-z can be identified in dee...