The cosmic evolution of the field galaxy population has been studied out to a redshift of z ∼ 1 using a sample of 730 I-band selected galaxies, of which 591 have secure redshifts with median < z >∼ 0.56. The tri-variate luminosity function φ(M, color, z) shows unambiguously that the population evolves and that this evolution is strongly differential with color and, less strongly, with luminosity. The luminosity function of red galaxies shows very little change in either number density or luminosity over the entire redshift range 0 < z < 1. In contrast, the luminosity function of blue galaxies shows substantial evolution at redshifts z > 0.5. By 0.5 < z < 0.75 the blue luminosity function appears to have uniformly brightened by approximately 1 magnitude. At higher redshifts, the evolution appears to saturate at the brightest magnitudes but continues at fainter levels leading to a steepening of the luminosity function. A significant excess of galaxies relative to the Loveday et al. (1992) local luminosity function is seen at low redshifts z < 0.2 around M AB (B) ∼ −18 and these galaxies may possibly represent the descendants of the evolving blue population seen at higher redshifts. The changes seen in the luminosity function are also apparent in color-magnitude diagrams constructed at different epochs and in the V /V max statistic computed as a function of spectral type. Finally, it is argued that the picture of galaxy evolution presented here is consistent with the very much smaller samples of field galaxies that have been selected in other wavebands, and with the results of studies of galaxies selected on the basis of Mg II 2799 absorption

X-shooter is the first 2nd generation instrument of the ESO Very Large Telescope (VLT). It is a very efficient, single-target, intermediate-resolution spectrograph that was installed at the Cassegrain focus of UT2 in 2009. The instrument covers, in a single exposure, the spectral range from 300 to 2500 nm. It is designed to maximize the sensitivity in this spectral range through dichroic splitting in three arms with optimized optics, coatings, dispersive elements and detectors. It operates at intermediate spectral resolution (R ∼ 4000−17 000, depending on wavelength and slit width) with fixed échelle spectral format (prism cross-dispersers) in the three arms. It includes a 1.8 × 4 integral field unit as an alternative to the 11 long slits. A dedicated data reduction package delivers fully calibrated two-dimensional and extracted spectra over the full wavelength range. We describe the main characteristics of the instrument and present its performance as measured during commissioning, science verification and the first months of science operations.

We present the first results of a deep unbiased submillimetre survey carried out at 450 and 850µm. We detected 12 sources at 850 µm, giving a surface density of sources with S 850µm > 2.8 mJy of 0.49 ± 0.16 arcmin −2 . The sources constitute 20-30% of the background radiation at 850µm and thus a significant fraction of the entire background radiation produced by stars. This implies, through the connection between metallicity and background radiation, that a significant fraction of all the stars that have ever been formed were formed in objects like those detected here. The combination of their large contribution to the background radiation and their extreme bolometric luminosities make these objects excellent candidates for being proto-ellipticals. Optical astronomers have recently shown that the UV -luminosity density of the universe increases by a factor of ≃10 between z = 0 and z = 1 − 2 and then decreases again at higher redshifts. Using the results of a parallel submillimetre survey of the local universe, we show that both the submillimetre source density and background can be explained if the submillimetre luminosity density evolves in a similar way to the UV -luminosity density. Thus, if these sources are ellipticals in the process of formation, they may be forming at relatively modest redshifts.

The early Universe had a chemical composition consisting of hydrogen, helium and traces of lithium 1 , almost all other elements were created in stars and supernovae. The mass fraction, Z, of elements more massive than helium, is called "metallicity". A number of very metal poor stars have been found 2,3 , some of which, while having a low iron abundance, are rich in carbon, nitrogen and oxygen 4,5,6 . For theoretical reasons 7,8 and because of an observed absence of stars with metallicities lower than Z=1.5×10 5 , it has been suggested that low mass stars (M‹0.8M ⊙ , the ones that survive to the present day) cannot form until the interstellar medium has been enriched above a critical value, estimated to lie in the range 1.5×10 8 ≤Z≤1.5×10 6[8] , although competing * Gliese Fellow