We estimate the galaxy stellar mass function and stellar mass density for star-forming and quiescent galaxies with 0.2 < z < 4. We construct a large, deep (K s < 24) sample of 220 000 galaxies selected using the new UltraVISTA DR1 data release. Our analysis is based on precise 30-band photometric redshifts. By comparing these photometric redshifts with 10,800 spectroscopic redshifts from the zCOSMOS bright and faint surveys, we find a precision of σ Δz/(1+z) = 0.008 at i + < 22.5 and σ Δz/(1+z) = 0.03 at 1.5 < z < 4. We derive the stellar mass function and correct for the Eddington bias. We find a mass-dependent evolution of the global and starforming populations, with the low-mass end of the mass functions evolving more rapidly than the high-mass end. This mass-dependent evolution is a direct consequence of the star formation being "quenched" in galaxies more massive than M 10 10.7−10.9 M . For the mass function of the quiescent galaxies, we do not find any significant evolution of the high-mass end at z < 1; however we observe a clear flattening of the faint-end slope. From z ∼ 3 to z ∼ 1, the density of quiescent galaxies increases over the entire mass range. Their comoving stellar mass density increases by 1.6 dex between z ∼ 3 and z ∼ 1 and by less than 0.2 dex at z < 1. We infer the star formation history from the mass density evolution. This inferred star formation history is in excellent agreement with instantaneous star formation rate measurements at z < 1.5, while we find differences of 0.2 dex at z > 1.5 consistent with the expected uncertainties. We also develop a new method to infer the specific star formation rate from the mass function of star-forming galaxies. We find that the specific star formation rate of 10 10−10.5 M galaxies increases continuously in the redshift range 1 < z < 4. Finally, we compare our results with a semi-analytical model and find that these models overestimate the density of low mass quiescent galaxies by an order of magnitude, while the density of low-mass star-forming galaxies is successfully reproduced.Key words. galaxies: distances and redshifts -galaxies: evolution -galaxies: formation -galaxies: star formationgalaxies: stellar content Based on data products from observations made with ESO Telescopes at the La Silla Paranal Observatory under ESO programme ID 179.A-2005 and on data products produced by TERAPIX and the Cambridge Astronomy Survey Unit on behalf of the UltraVISTA consortium.Catalogues are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via

Three billion years after the big bang (at redshift z = 2), half of the most massive galaxies were already old, quiescent systems with little to no residual star formation and extremely compact with stellar mass densities at least an order of magnitude larger than in low redshift ellipticals, their descendants. Little is known about how they formed, but their evolved, dense stellar populations suggest formation within intense, compact starbursts 1-2 Gyr earlier (at 3 < z < 6). Simulations show that gas-rich major mergers can give rise to such starbursts which produce dense remnants. Sub-millimeter selected galaxies (SMGs) are prime examples of intense, gas-rich, starbursts. With a new, representative spectroscopic sample of compact quiescent galaxies at z = 2 and a statistically wellunderstood sample of SMGs, we show that z = 3 − 6 SMGs are consistent with being the progenitors of z = 2 quiescent galaxies, matching their formation redshifts and their distributions of sizes, stellar masses and internal velocities. Assuming an evolutionary connection, their space densities also match if the mean duty cycle of SMG starbursts is 42 +40 −29 Myr (consistent with independent estimates), which indicates that the bulk of stars in these massive galaxies were formed in a major, early surge of star-formation. These results suggests a coherent picture of the formation history of the most massive galaxies in the universe, from their initial burst of violent star-formation through their appearance as high stellar-density galaxy cores and to their ultimate fate as giant ellipticals.

Quasi-stellar object (QSO) spectral templates are important both to QSO physics and for investigations that use QSOs as probes of intervening gas and dust. However, combinations of various QSO samples obtained at different times and with different instruments so as to expand a composite and to cover a wider rest frame wavelength region may create systematic effects, and the contribution from QSO hosts may contaminate the composite. We have constructed a composite spectrum from luminous blue QSOs at 1 < z < 2.1 selected from the Sloan Digital Sky Survey (SDSS). The observations with X-Shooter simultaneously cover ultraviolet (UV) to nearinfrared (NIR) light, which ensures that the composite spectrum covers the full rest-frame range from Lyβ to 11 350 Å without any significant host contamination. Assuming a power-law continuum for the composite we find a spectral slope of α λ = 1.70 ± 0.01, which is steeper than previously found in the literature. We attribute the differences to our broader spectral wavelength coverage, which allows us to effectively avoid fitting any regions that are affected either by strong QSO emissions lines (e.g., Balmer lines and complex [Fe II] blends) or by intrinsic host galaxy emission. Finally, we demonstrate the application of the QSO composite spectrum for evaluating the reddening in other QSOs.

Starting from a summary of detection statistics of our recent X-shooter campaign, we review the major surveys, both space and ground based, for emission counterparts of high-redshift damped Lyα absorbers (DLAs) carried out since the first detection 25 years ago. We show that the detection rates of all surveys are precisely reproduced by a simple model in which the metallicity and luminosity of the galaxy associated to the DLA follow a relation of the form,3 ) − 20.8, and the DLA cross-section follows a relation of the form σ DLA ∝ L 0.8 . Specifically, our spectroscopic campaign consists of 11 DLAs preselected based on their equivalent width of Si II λ1526 to have a metallicity higher than [Si/H] > −1. The targets have been observed with the X-shooter spectrograph at the Very Large Telescope to search for emission lines around the quasars. We observe a high detection rate of 64% (7/11), significantly higher than the typical ∼10% for random, H I-selected DLA samples. We use the aforementioned model, to simulate the results of our survey together with a range of previous surveys: spectral stacking, direct imaging (using the 'double DLA' technique), long-slit spectroscopy, and integral field spectroscopy. Based on our model results, we are able to reconcile all results. Some tension is observed between model and data when looking at predictions of Lyα emission for individual targets. However, the object to object variations are most likely a result of the significant scatter in the underlying scaling relations as well as uncertainties in the amount of dust which affects the emission.