We build a sample of 298 spectroscopically-confirmed galaxies at redshift z~2, selected in the z-band from the GOODS-MUSIC catalog. By exploiting the rest frame 8 um luminosity as a proxy of the star formation rate (SFR) we check the accuracy of the
standard SED-fitting technique, finding it is not accurate enough to provide reliable estimates of the galaxy physical parameters. We then develop a new SED-fitting method that includes the IR luminosity as a prior and a generalized Calzetti law with a variable RV . Then we exploit such a new method to re-analyze our galaxy sample, and to robustly determine SFRs, stellar masses and ages. We find that there is a general trend of increasing attenuation with the SFR. Moreover, we find that the SFRs range between a few to 1000 solar mass per year, the masses from one billion to 400 billion solar masses, while the ages from a few tens of Myr to more than 1 Gyr. We discuss how individual age easurements of highly attenuated objects indicate that dust must form within a few tens of Myr and be copious already at ~100 Myr. In addition, we find that low luminous galaxies harbor, on average, significantly older stellar populations and are also less massive than brighter ones; we discuss how these findings and the well known downsizing scenario are consistent in a framework where less massive galaxies form first, but their star formation lasts longer. Finally, we find that the near-IR attenuation is not scarce for luminous objects, contrary to what is customarily assumed; we discuss how this affects the interpretation of the observed mass-to-light ratios.
We compile a large sample of broad absorption lines (BAL) quasars with X-ray observations from the xmm archive data and Sloan Digital Sky Survey Data Release 5. The sample consists of 41 BAL QSOs. Among 26 BAL quasars detected in X-ray, spectral anal
ysis is possible for twelve objects. X-ray absorption is detected in all of them. Complementary to that of citet{gall06} (thereafter G06), our sample spans wide ranges of both BALnicity Index (BI) and maximum outflow velocity (vmax). Combining our sample with G06s, we find very significant correlations between the intrinsic X-ray weakness with both BALnicity Index (BI) and the maximum velocity of absorption trough. We do not confirm the previous claimed correlation between absorption column density and broad absorption line parameters. We tentatively interpret this as that X-ray absorption is necessary to the production of the BAL outflow, but the properties of the outflow are largely determined by intrinsic SED of the quasars.
