Disk galaxy evolution: from the Milky Way to high-redshift disks

We develop a detailed model of the Milky Way (a ``prototypical'' disk galaxy) and extend it to other disks with the help of some simple scaling relations, obtained in the framework of Cold Dark Matter models. This phenomenological (``hybrid'') approach to the study of disk galaxy evolution allows us to reproduce successfully a large number of observed properties of disk galaxies in the local Universe and up to redshift z~1. The important conclusion is that, on average, massive disks have formed the bulk of their stars earlier than their lower mass counterparts: the ``star formation hierarchy'' has been apparently opposite to the ``dark matter assembly'' hierarchy. It is not yet clear whether ``feedback'' (as used in semi-analytical models of galaxy evolution) can explain that discrepancy.Comment: 12 pages, 8 figures. Invited talk in "Galaxy Evolution III: From Simple Approaches to Self-Consistent Models" (Kiel, Germany, July 16-20, 2002) Eds. G. Hensler et al., in pres

Chemo-spectrophotometric evolution of spiral galaxies: III. Abundance and colour gradients in discs

We study the relations between luminosity and chemical abundance profiles of spiral galaxies, using detailed models for the chemical and spectro-photometric evolution of galactic discs. The models are ``calibrated'' on the Milky Way disc and are successfully extended to other discs with the help of simple ``scaling'' relations, obtained in the framework of semi-analytic models of galaxy formation. We find that our models exhibit oxygen abundance gradients that increase in absolute value with decreasing disc luminosity (when expressed in dex/kpc) and are independent of disc luminosity (when expressed in dex/scalelength), both in agreement with observations. We notice an important strong correlation between abundance gradient and disc scalelength. These results support the idea of ``homologuous evolution'' of galactic discs.Comment: 9 pages, 6 postscript figures, MNRAS in pres

Metallicity in damped Lyman-alpha systems: evolution or bias?

Assuming that damped Lyman-alpha(DLA) systems are galactic discs, we calculate the corresponding evolution of metal abundances. We use detailed multi-zone models of galactic chemical evolution (reproducing successfully the observed properties of disc galaxies) and appropriate statistics (including geometrical propability factors) to calculate the average metallicity as a function of redshift. The results are compatible with available observations, provided that observational biases are taken into account, as suggested by Boisse et al. (1998). In particular, high column density and high metallicity systems are not detected because the light of backround quasars is severely extinguished, while low column density and low metallicity systems are not detectable through their absorption lines by current surveys. We show that these observational constraints lead to a ``no-evolution'' picture for the DLA metallicity, which does not allow to draw strong conclusions about the nature of those systems or about their role in ``cosmic chemical evolution''.Comment: 7 pages, 5 figures, MNRAS in pres

The chemical evolution of the Milky Way in a cosmological context

A short overview is presented of several topics concerning the evolution of the Milky Way (MW) in a cosmological context. In particular, the metallicity distribution of the MW halo is derived analytically and the halo metallicity and abundance patterns are compared to those of Local Group galaxies. The inside-out formation of the MW disk is supported by the observed evolution of the abundance gradients, while their magnitude suggests that the role of the Galactic bar has been negligible. Finally, the empirical foundations (age-metallicity relation and metallicity distribution) of the evolution of the solar neighborhood, which is the best studied galactic sub-system, have been seriously questioned recently.Comment: 12 pages, 17 figures. Invited review at CRAL-Conference Series I "Chemodynamics: from first stars to local galaxies" (Lyon 10-14 July 2006), Eds. Emsellem, Wozniak, Massacrier, Gonzalez, Devriendt, Champavert, EAS Publications Serie

Chemical evolution and depletion pattern in Damped Lyman-alpha (DLA) systems

In this paper we point out a previously unnoticed anticorrelation between the observed abundance ratio [X/Zn] (where Zn is assumed to be undepleted and X stands for the refractories Fe, Cr and Ni) and metal column density ([Zn/H]+log(N{HI})) in DLAs. We suggest that this trend is an unambiguous sign of dust depletion, since metal column density is a measure of the amount of dust along the line of sight. Assuming that DLAs are (proto-)galactic disks and using detailed chemical evolution models with metallicity dependent yields we study chemical evolution and dust depletion patterns for alpha and iron-peak elements in DLAs. When observational constraints on the metal column density of DLAs are taken into account (as suggested in Boisse et al. 1998) we find that our models reproduce fairly well the observed mild redshift evolution of the abundances of 8 elements (Al, Si, S, Cr, Mn, Fe, Zn and Ni) as well as the observed scatter at a given redshift. By considering the aforementioned dependence of abundance ratios on metal column density, we further explore the general dust depletion pattern in DLAs, comparing to our model results and to a solar reference pattern. We suggest that further measurements of the key elements, i.e. Zn, S and Mn, will help to gain more insight into the nature of DLAs. In any case, the presently uncertain nucleosynthesis of Zn in massive stars (on which a large part of these conclusions is based) should be carefully scrutinised.Comment: 12 pages, 4 figures, Astronomy and Astrophysics, in pres

Perspectives in Galactic Chemical Evolution studies

In this review I focus on a few selected topics, where recent theoretical and/or observational progress has been made and important developments are expected in the future. They include: 1) Evolution of isotopic ratios, 2) Mixing processes and dispersion in abundance ratios, 3) Abundance gradients in the Galactic disk (and abundance patterns in the inner Galaxy), 4) The question of primary Nitrogen and 5) Abundance patterns in extragalactic damped Lyman-alpha systems (DLAs)

Metallicity-dependendent kinematics and morphology of the Milky Way bulge

We use N-body chemo-dynamic simulations to study the coupling between morphology, kinematics and metallicity of the bar/bulge region of our Galaxy. We make qualitative comparisons of our results with available observations and find very good agreement. We conclude that this region is complex, since it comprises several stellar components with different properties -- i.e. a boxy/peanut bulge, thin and thick disc components, and, to lesser extents, a disky pseudobulge, a stellar halo and a small classical bulge -- all cohabiting in dynamical equilibrium. Our models show strong links between kinematics and metallicity, or morphology and metallicity, as already suggested by a number of recent observations. We discuss and explain these links.Comment: 5 pages, 4 figures, accepted for publication in MNRAS Letter