2006AJ....131.1891F

We present deep near-infrared J_s-, H-, and K_s-band imaging of a field around MS 1054-03, a massive cluster at z=0.83. The observations were carried out with the ISAAC instrument at the ESO Very Large Telescope (VLT) as part of the Faint Infrared Extragalactic Survey (FIRES). The total integration time amounts to 25.9 hr in J_s_, 24.4 hr in H, and 26.5 hr in K_s, divided nearly equally between four pointings covering 5'.5x5'.3. The 3 σ total limiting AB magnitudes for point sources from the shallowest to the deepest pointing are J^tot_s,AB=26.0-26.2, H^tot_AB=25.5-25.8, and K^tot_s,AB=25.3-25.7 mag. The effective spatial resolution of the co-added images has FWHM=0".48, 0".46, and 0".52 in J_s, H, and K_s, respectively. We complemented the ISAAC data with deep optical imaging using existing Hubble Space Telescope WFPC2 mosaics through the F606W and F814W filters and additional U-, B-, and V-band observations we obtained with the VLT FORS1 instrument. We constructed a K_s-band-limited multicolor source catalog down to K^tot_s,AB~25 mag (~5 σ for point sources). The catalog contains 1858 objects, of which 1663 have eight-band photometry. We describe the observations, data reduction, source detection, and photometric measurements method. We also present the number counts, color distributions, and photometric redshifts z_phof the catalog sources. We find that our K_s-band counts at the faint end 22≲K_s,AB≲25, with slope dlogN/dm=0.20, lie at the flatter end of published counts in other deep fields and are consistent with those we derived previously in the Hubble Deep Field-South (HDF-S), the other FIRES field. Spectroscopic redshifts z_spare available for ~330 sources in the MS 1054-03 field; comparison between z_phand z_spshows very good agreement, with <|z_sp-z_ph|/(1+z_sp)≥0.078. The MS 1054-03 field observations complement our HDF-S data set with a nearly 5 times larger area at ~0.7 mag brighter limits, providing more robust statistics for the slightly brighter source populations.