Seeking for the leading actor on the cosmic stage: Galaxies versus Supermassive Black Holes

We present a Special Issue on the interplay of galaxies and Supermassive Black Holes (SMBHs) recently published in Advances in Astronomy. This is the introductory paper containing the motivation for this Special Issue together with a brief description of the articles which are part of the manuscript and the link to the entire book (http://www.hindawi.com/journals/aa/si/610485/). We hope this Special Issue will be useful for many astronomers who want to get an update on the current status of the AGN-Galaxy coevolution topic.Comment: 4 pages, published in Advances in Astronomy as Introductory paper to the Special Issue "Seeking for the leading actor on the cosmic stage: Galaxies versus SMBHs". The entire book can be downloaded as PDF here: http://www.hindawi.com/journals/aa/si/610485

Evolution of the Mass-Metallicity relations in passive and star-forming galaxies from SPH-cosmological simulations

We present results from SPH-cosmological simulations, including self-consistent modelling of SN feedback and chemical evolution, of galaxies belonging to two clusters and twelve groups. We reproduce the mass-metallicity (ZM) relation of galaxies classified in two samples according to their star-forming activity, as parametrized by their sSFR, across a redshift range up to z=2. Its slope shows irrelevant evolution in the passive sample, being steeper in groups than in clusters. However, the sub-sample of high-mass passive galaxies only is characterized by a steep increase of the slope with redshift, from which it can be inferred that the bulk of the slope evolution of the ZM relation is driven by the more massive passive objects. (...ABRIDGED...) The ZM relation for the star-forming sample reveals an increasing scatter with redshift, indicating that it is still being built at early epochs. The star-forming galaxies make up a tight sequence in the SFR-M_* plane at high redshift, whose scatter increases with time alongside with the consolidation of the passive sequence. We also confirm the anti-correlation between sSFR and stellar mass, pointing at a key role of the former in determining the galaxy downsizing, as the most significant means of diagnostics of the star formation efficiency. Likewise, an anti-correlation between sSFR and metallicity can be established for the star-forming galaxies, while on the contrary more active galaxies in terms of simple SFR are also metal-richer. We discuss these results in terms of the mechanisms driving the evolution within the high- and low-mass regimes at different epochs: mergers, feedback-driven outflows and the intrinsic variation of the star formation efficiency.Comment: Emended list of author

Vignobles du sud, XVIe-XXe siècle

Programme du colloque Vendredi 16 mars 2001 - Matin (Salle Pierre-Jourda) 9h : Ouverture du colloque Allocution de Michèle WEIL, présidente de l'Université Montpellier III Présentation par Henri MICHEL, directeur du Centre d'histoire moderne et contemporaine, directeur de l'UFR III Introduction par Geneviève GAVIGNAUD-FONTAINE, professeur responsable du colloque 9h45 : Vignes et vins méditerranéens Président de séance, Daniel LE BLEVEC (Université Montpellier III) Gilbert LARGUIER..

Hommage à Michel Peronnet (1931-1998)

La Commission régionale d'Histoire de la Révolution française Languedoc-Roussillon a perdu son Président-fondateur. Professeur à l'Université de Montpellier, Michel Péronnet avait institutionnalisé, dès 1984-1985, la préparation du Bicentenaire de la Révolution de 1789, dans la mouvance de la réputée Commission nationale, fort active depuis son siège parisien, sous l'autorité de Michel Vovelle. Par cette décision, le Président Péronnet avait engagé une équipe dont il avait pris la tête avec e..

A study on the multicolour evolution of Red Sequence galaxy populations: insights from hydrodynamical simulations and semi-analytical models

By means of our own cosmological-hydrodynamical simulation and semi-analytical model we studied galaxy population properties in clusters and groups, spanning over 10 different bands from UV to NIR, and their evolution since redshift z=2. We compare our results in terms of galaxy red/blue fractions and luminous-to-faint ratio (LFR) on the Red Sequence (RS) with recent observational data reaching beyond z=1.5. Different selection criteria were tested in order to retrieve galaxies belonging to the RS: either by their quiescence degree measured from their specific SFR ("Dead Sequence"), or by their position in a colour-colour plane which is also a function of sSFR. In both cases, the colour cut and the limiting magnitude threshold were let evolving with redshift, in order to follow the natural shift of the characteristic luminosity in the LF. We find that the Butcher-Oemler effect is wavelength-dependent, with the fraction of blue galaxies increasing steeper in optical colours than in NIR. Besides, only when applying a lower limit in terms of fixed absolute magnitude, a steep BO effect can be reproduced, while the blue fraction results less evolving when selecting samples by stellar mass or an evolving magnitude limit. We then find that also the RS-LFR behaviour, highly debated in the literature, is strongly dependent on the galaxy selection function: in particular its very mild evolution recovered when measured in terms of stellar mass, is in agreement with values reported for some of the highest redshift confirmed (proto)clusters. As to differences through environments, we find that normal groups and (to a lesser extent) cluster outskirts present the highest values of both star forming fraction and LFR at low z, while fossil groups and cluster cores the lowest: this separation among groups begins after z~0.5, while earlier all group star forming properties are undistinguishable.Comment: revised version, A&A accepted (11 pages, 6 figures

The cosmic growth of the active black hole population at 1<z<2 in zCOSMOS, VVDS and SDSS

We present a census of the active black hole population at 1<z<2, by constructing the bivariate distribution function of black hole mass and Eddington ratio, employing a maximum likelihood fitting technique. The study of the active black hole mass function (BHMF) and the Eddington ratio distribution function (ERDF) allows us to clearly disentangle the active galactic nuclei (AGN) downsizing phenomenon, present in the AGN luminosity function, into its physical processes of black hole mass downsizing and accretion rate evolution. We are utilizing type-1 AGN samples from three optical surveys (VVDS, zCOSMOS and SDSS), that cover a wide range of 3 dex in luminosity over our redshift interval of interest. We investigate the cosmic evolution of the AGN population as a function of AGN luminosity, black hole mass and accretion rate. Compared to z = 0, we find a distinct change in the shape of the BHMF and the ERDF, consistent with downsizing in black hole mass. The active fraction or duty cycle of type-1 AGN at z~1.5 is almost flat as a function of black hole mass, while it shows a strong decrease with increasing mass at z=0. We are witnessing a phase of intense black hole growth, which is largely driven by the onset of AGN activity in massive black holes towards z=2. We finally compare our results to numerical simulations and semi-empirical models and while we find reasonable agreement over certain parameter ranges, we highlight the need to refine these models in order to match our observations.Comment: 31 pages, 28 figures, accepted for publication in MNRA