AGN feedback from Jet-ISM/IGM interactions

We study the propagation of relativistic jets originating from AGNs within the Interstellar/Intergalactic Medium of their host galaxies, and use it to build a model for the suppression of stellar formation within the expanding cocoon.Comment: 2 pages, 3 figures. Poster presented at IAU Symp. no. 245 ("Formation and Evolution of Galaxy Bulges"), Oxford, July 16-20, 200

Feedback in Galaxy Formation

I review the outstanding problems in galaxy formation theory, and the role of feedback in resolving them. I address the efficiency of star formation, the galactic star formation rate, and the roles of supernovae and supermassive black holes.Comment: To appear in the proceedings of IAU Symposium 277, Burkina Faso, December 2010, Tracing the Ancestry of Galaxies (on the Land of our Ancestors), C. Carignan, F. Combes \& K. Freeman, ed

On the Dynamical Origin of Bias in Clusters of Galaxies

We study the effect of the dynamical friction induced by the presence of substructure on the statistics of the collapse of density peaks. Applying the results of a former paper we show that within high density environments, like rich clusters of galaxies, the collapse of smaller peaks is strongly delayed until very late epochs. A bias of dynamical nature thus naturally arises because high density peaks preferentially collapse For a standard CDM model we find that this dynamical bias can account for a substantial part of the total bias required by observations on cluster scales.Comment: 14 pages, postscript, 3 postscript figures available by anonymous ftp on convex.ct.astro.it in /nbody/fig#.ps. Submitted to Astrophysical Journal Letter