The WIRCam Deep Survey

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 similar to 0.6 '') J, H, and K-s imaging covering a total effective area of 2.1 deg(2) and reaching AB 50% completeness limits of approximate to 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 approximate to 9800 spectroscopic redshifts to estimate precise photometric redshifts (sigma(Delta z/(1+z)) less than or similar to 0.03 at i < 25), galaxy types, star-formation rates and stellar masses for a unique sample of approximate to 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 less than or similar to 10(10.75) still evolving at z less than or similar to 1, but galaxies of higher mass reaching their present day numbers by z similar to 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 less than or similar to log (M/M-circle dot) less than or similar to 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 circle dot) less than or similar to 10), whilst the fit as a whole degrades beyond redshifts of z similar to 1.2. All photometric catalogues and images are made publicly available from TERAPIX and CADC.