2018A&A...620A..51P

The aim of this paper is to introduce the WIRCam Ultra Deep Survey (WUDS), a near-IR photometric survey carried out at the CFH Telescope in the field of the CFHTLS-D3 field (Groth Strip). WUDS includes four near-IR bands (Y, J, H and K_s) over a field of view of ∼400-arcmin². The typical depth of WUDS data reaches between ∼26.8 in Y and J, and ∼26 in H and K_s (AB, 3σ in 1.3'' aperture), whereas the corresponding depth of the CFHTLS-D3 images in this region ranges between 28.6 and 29 in ugr, 28.2 in i and 27.1 in z (same S/N and aperture). The area and depth of this survey were specifically tailored to set strong constraints on the cosmic star formation rate and the luminosity function brighter or around L* in the z∼6-10 redshift domain, although these data are also useful for a variety of extragalactic projects. This first paper is intended to present the properties of the public WUDS survey in details: catalog building, completeness and depth, number counts, photometric redshifts, and global properties of the galaxy population. We have also concentrated on the selection and characterization of galaxy samples at z~[4.5-7] in this field. For these purposes, we include an adjacent shallower area of ∼1260-arcmin² in this region, extracted from the WIRCam Deep Survey (WIRDS), and observed in J, H and K_s bands. UV luminosity functions were derived at z∼5 and z∼6 taking advantage from the fact that WUDS covers a particularly interesting regime at intermediate luminosities, which allows a combined determination of M* and Φ* with increased accuracy. Our results on the luminosity function are consistent with a small evolution of both M* and Φ* between z=5 and z=6, irrespective of the method used to derive them, either photometric redshifts applied to blindly-selected dropout samples or the classical Lyman Break Galaxy color-preselected samples. Our results lend support to higher Φ* determinations at z=6 than usually reported. The selection and combined analysis of different galaxy samples at z≥7 will be presented in a forthcoming paper, as well as the evolution of the UV luminosity function between z∼4.5 and 9. WUDS is intended to provide a robust database in the near-IR for the selection of targets for detailed spectroscopic studies, in particular for the EMIR/GTC GOYA Survey.