The WIRCam Deep Survey

I. Counts, colours, and mass-functions derived from near-infrared imaging in the CFHTLS deep fields^⋆

¹ Institut dAstrophysique de Paris, UMR 7095 CNRS, Université Pierre et Marie Curie, 98bis boulevard Arago, 75014 Paris, France
e-mail: rmbielby@gmail.com
² Dept. of Physics, Durham University, South Road, Durham, DH1 3LE, UK
³ Laboratoire d’Astrophysique de Marseille, Université Aix-Marseille, 38 rue Frédéric Joliot-Curie, 13388 Marseille, France
⁴ Service d’Astrophysique, CEA/Saclay, 91191 Gif-sur-Yvette, France
⁵ Laboratoire IDES, UMR 8148 CNRS, Université Paris-Sud XI, 91405 Orsay, France
⁶ Max Planck Institut für Plasma Physik and Excellence Cluster, Boltzmannstrasse 2, 85748 Garching, Germany
⁷ Institute for Astronomy, 2680 Woodlawn Dr., University of Hawaii, Honolulu, HI 96822, USA
⁸ Herzberg Institute of Astrophysics, National Research Council, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada

Received: 29 November 2011
Accepted: 13 June 2012

Abstract

We present a new near-infrared imaging survey in the four CFHTLS deep fields: the WIRCam Deep Survey or “WIRDS”. WIRDS comprises extremely deep, high quality (FWHM ~ 0.6″) J, H, and K_s imaging covering a total effective area of 2.1   deg² and reaching AB 50% completeness limits of  ≈ 24.5. We combine our images with the CFHTLS to create a unique eight-band ugrizJHK_S photometric catalogues in the four CFHTLS deep fields; these four separate fields allow us to make a robust estimate of the effect of cosmic variance for all our measurements. We use these catalogues in combination with  ≈ 9800 spectroscopic redshifts to estimate precise photometric redshifts (σ_{Δz/(1 + z)} ≲ 0.03 at i < 25), galaxy types, star-formation rates and stellar masses for a unique sample of  ≈ 1.8 million galaxies. Our JHK_s number counts are consistent with previous studies. We apply the “BzK” selection to our gzK filter set and find that the star forming BzK selection successfully selects 76% of star-forming galaxies in the redshift range 1.4 < z < 2.5 in our photometric catalogue, based on our photometric redshift measurement. Similarly the passive BzK selection returns 52% of the passive 1.4 < z < 2.5 population identified in the photometric catalogue. We present the mass functions of the total galaxy population as a function of redshift up to z = 2 and present fits using double Schechter functions. A mass-dependent evolution of the mass function is seen with the numbers of galaxies with masses of M ≲ 10^10.75 still evolving at z ≲ 1, but galaxies of higher mass reaching their present day numbers by z ~ 0.8−1. This is consistent with the present picture of downsizing in galaxy evolution. We compare our results with the predictions of the GALFORM semi-analytical galaxy formation model and find that the simulations provide a relatively successful fit to the observed mass functions at intermediate masses (i.e. 10 ≲ log    (M/M_⊙) ≲ 11). However, as is common with semi-analytical predictions of the mass function, the GALFORM results under-predict the mass function at low masses (i.e. log    (M/M_⊙) ≲ 10), whilst the fit as a whole degrades beyondredshifts of z ~ 1.2. All photometric catalogues and images are made publicly available from TERAPIX and CADC.