Abstract
We present the VIMOS Ultra Deep Survey (VUDS), a spectroscopic redshift survey of ~10.000 very faint galaxies to study the major phase of galaxy assembly 2<z<~6. The survey covers 1 deg^2 in 3 separate fields: COSMOS, ECDFS and VVDS-02h, with targets selection based on an inclusive combination of photometric redshifts and color properties. Spectra covering 3650<lambda<9350 A are obtained with VIMOS on the ESO-VLT with integration times of 14h. Here we present the survey strategy, the target selection, the data processing, as well as the redshift measurement process, emphasizing the specific methods adapted to this high redshift range. The spectra quality and redshift reliability are discussed, and we derive a completeness in redshift measurement of 91%, or 74% for the most reliable measurements, down to i_AB=25, and measurements are performed all the way down to i_AB=27. The redshift distribution of the main sample peaks at z=3-4 and extends over a large redshift range mainly in 2 < z < 6. At 3<z<5, the galaxies cover a large range of luminosities -23< M_U < -20.5, stellar mass 10^9 M_sun< M_star < 10^{11} M_sun, and star formation rates 1 M_sun/yr< SFR < 10^3 M_sun/yr. We discuss the spectral properties of galaxies using individual as well as stacked spectra. The comparison between spectroscopic and photometric redshifts as well as color selection demonstrate the effectiveness of our selection scheme. With ~6000 galaxies with reliable spectroscopic redshifts in 2<z<6 expected when complete, this survey is the largest at these redshifts and offers the opportunity for unprecedented studies of the star-forming galaxy population and its distribution in large scale structures during the major phase of galaxy assembly.
Highlights
The study of the first billion years of galaxy evolution is one of the key frontiers of modern cosmology
We present the VIsible Multi-Object Spectrograph (VIMOS) Ultra Deep Survey (VUDS), a spectroscopic redshift survey of ∼10 000 very faint galaxies to study the main phase of galaxy assembly in 2 < z 6
The VIMOS Ultra Deep Survey (VUDS) is a deep spectroscopic redshift survey aiming to study the early phases of galaxy assembly at 2 < z < 6.5 from a sample of ∼10 000 galaxies observed with the VIMOS multi-slit spectrograph at the ESO-VLT
Summary
The study of the first billion years of galaxy evolution is one of the key frontiers of modern cosmology. Deep surveys are providing a complex picture with strong evolutionary features such as the build-up of stellar mass in galaxies of different types during cosmic time, or the star formation history. It was realised that a colour–colour selection such as the LBG technique at z > 2.5 or the BzK, which works at z 2 (Daddi et al 2004), would miss a part of the general galaxy population in their selection process (Le Fèvre et al 2005a), which would cause the galaxy census to be incomplete (Le Fèvre et al 2013a) The consequences of this may be far-reaching, as incompleteness in counts leads to underestimates in luminosity density, star formation rates, or mass density, to cite just a few consequences. To overcome the uncertainties linked to small existing spectroscopic samples and to understand the biases and limitations of photometry-based studies in their ability to provide a complete census of the galaxy population, extremely deep spectroscopic surveys over large volumes are needed.
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