We present initial results of an ESO-VLT large programme (AMAZE) aimed at determining the evolution of the mass-metallicity relation at z > 3 by means of deep near-IR spectroscopy. Gas metallicities are measured, for an initial sample of nine star forming galaxies at z ∼ 3.5, by means of optical nebular lines redshifted into the near-IR. Stellar masses are accurately determined by using Spitzer-IRAC data, which sample the rest-frame near-IR stellar light in these distant galaxies. When compared with previous surveys, the mass-metallicity relation inferred at z ∼ 3.5 shows an evolution much stronger than observed at lower redshifts. The evolution is prominent even in massive galaxies, indicating that z ∼ 3 is an epoch of major action in terms of star formation and metal enrichment also for massive systems. There are also indications that the metallicity evolution of low mass galaxies is stronger relative to high mass systems, an effect which can be considered the chemical version of the galaxy downsizing. The mass-metallicity relation observed at z ∼ 3.5 is difficult to reconcile with the predictions of some hierarchical evolutionary models. Such discrepancies suggest that at z > 3 galaxies are assembled mostly with relatively un-evolved sub-units, i.e. small galaxies with low star formation efficiency. The bulk of the star formation and metallicity evolution probably occurs once small galaxies are already assembled into bigger systems.

We have determined the cosmological evolution of the density of active galactic nuclei (AGN) and of their N H distribution as a function of the un-absorbed 2-10 keV luminosity up to redshift 4. We used the HELLAS2XMM sample combined with other published catalogs, yielding a total of 508 AGN. Our best fit is obtained with a luminosity-dependent density evolution (LDDE) model where low luminosity (L X ∼10 43 erg s −1 ) AGN peak at z∼0.7, while high luminosity AGN (L X >10 45 erg s −1 ) peak at z∼2.0. A pure luminosity evolution model (PLE) can instead be rejected.There is evidence that the fraction of absorbed (N H >10 22 cm −2 ) AGN decreases with the intrinsic X-ray luminosity, and increases with the redshift.Our best fit solution provides a good fit to the observed counts, the cosmic X-ray background, and to the observed fraction of absorbed AGN as a function of the flux in the 10 −15 10 44 erg s −1 ) AGN have a density of 267 deg −2 at fluxes S 2−10 >10 −15 erg cm −2 s −1 . Using these results, we estimate a density of supermassive black holes in the local Universe of ρ BH = 3.2 h 2 70 × 10 5 M ⊙ Mpc −3 , which is consistent with the recent measurements of the black hole mass function in the local galaxies.

Abstract. We present results from the photometric and spectroscopic identification of 122 X-ray sources recently discovered by XMM-Newton in the 2-10 keV band (the HELLAS2XMM 1dF sample). Their flux cover the range 8 × 10 −15 −4 × 10 −13 erg cm −2 s −1 and the total area surveyed is 0.9 square degrees. One of the most interesting results (which is found also in deeper sourveys) is that about 20% of the hard X-ray selected sources have an X-ray to optical flux ratio (X/O) ten times or more higher than that of optically selected AGN. Unlike the faint sources found in the ultra-deep Chandra and XMM-Newton surveys, which reach X-ray (and optical) fluxes more than one order of magnitude lower than the HELLAS2XMM survey sources, many of the extreme X/O sources in our sample have R < ∼ 25 and are therefore accessible to optical spectroscopy. We report the identification of 13 sources with X/O > ∼ 10 (to be compared with 9 sources known from the deeper, pencil-beam surveys). Eight of them are narrow line QSO (seemingly the extension to very high luminosity of the type 2 Seyfert galaxies), four are broad line QSO. The results from our survey are also used to make reliable predictions about the luminosity of the sources not yet spectroscopically identified, both in our sample and in deeper Chandra and XMM-Newton samples. We then use a combined sample of 317 hard X-ray selected sources (HELLAS2XMM 1dF, Chandra Deep Field North 1Msec, Chandra SSA13 and XMM-Newton Lockman Hole flux limited samples), 221 with measured redshifts, to evaluate the cosmological evolution of the hard X-ray source's number and luminosity densities. Looking backward in time, the low luminosity sources (log L 2−10 keV = 43−44 erg s −1 ) increase in number at a much slower rate than the very high luminosity sources (log L 2−10 keV > 44.5 erg s −1 ), reaching a maximum around z = 1 and then levelling off beyond z = 2. This translates into an accretion driven luminosity density which is dominated by sources with log L 2−10 keV < 44.5 erg s −1 up to at least z = 1, while the contribution of the same sources and of those with log L 2−10 keV > 44.5 erg s −1 appear, with yet rather large uncertainties, to be comparable between z = 2 and 4.

We present a SINFONI integral-field kinematical study of 33 galaxies at z ∼ 3 from the AMAZE and LSD projects, which are aimed at studying metallicity and dynamics of high-redshift galaxies. The number of galaxies analyzed in this paper constitutes a significant improvement over existing data in the literature, and this is the first time that a dynamical analysis is obtained for a relatively large sample of galaxies at z ∼ 3. Eleven galaxies show ordered rotational motions (∼30% of the sample). In these cases we estimate dynamical masses by modeling the gas kinematics with rotating disks and exponential mass distributions. We find dynamical masses in the range 2 × 10 9 M −2 × 10 11 M with a mean value of ∼2 × 10 10 M . By comparing observed gas velocity dispersion with what is expected from models, we find that most rotating objects are dynamically "hot", with intrinsic velocity dispersions of ∼90 km s −1 . The median value of the ratio between the maximum disk rotational velocity and the intrinsic velocity dispersion for the rotating objects is 1.6, much lower than observed in local galaxies value (∼10) and slightly lower than the z ∼ 2 value (2-4). Finally we use the maximum rotational velocity from our modeling to build a baryonic Tully-Fisher relation at z ∼ 3. Our measurements indicate that z ∼ 3 galaxies have lower stellar masses (by a factor of ten on average) compared to local galaxies with the same dynamical mass. However, the large observed scatter suggests that the Tully-Fisher relation is not yet "in place" at these early cosmic ages, possibly owing to the young age of galaxies. A smaller dispersion of the Tully-Fisher relation is obtained by taking the velocity dispersion into account with the use of the S 0.5 indicator, suggesting that turbulent motions might play an important dynamical role.