Program: GN-2008B-C-3

We propose 4 nights with Gemini--North and NIRI to study the effects of feedback in the ISM of massive, star-forming (SF) galaxies at $2.2<z<2.6$ (sBzK), with and without luminous Compton--thick (CT) AGN hosted in them. We will measure the velocity and geometry of the large--scale motions of the interstellar gas from the redshift difference between the \halpha\ line, which traces the systemic redshift, and the UV low-ionization interstellar absorption lines and \lya, whose spectra we already have. This is the same methodology used to study galactic winds in Lyman--break galaxies at $z\sim 2$--3 (BX/LBG). The key new element here is that the SF rate and stellar mass of the selected sBzK are $~\sim 10\times$ higher than those of their BX/LBG counterparts at the same redshift, and half of them host a luminous, Compton--tick AGN. We will study if the feedback depends on the presence of a powerful CT AGN, whose energy is absorbed and re--irradiated by the ISM, but the fraction retained as mechanical energy is unknown. By comparing with the LBG, we will also study how the feedback depends on SF rate and mass. These observations will be one of the first attempts to provide empirical information on feedback and its relationship with physical properties of galaxies at the cosmic time when some massive galaxies were already passively evolving.