Near-IR Galaxy Counts and Evolution from the Wide-Field ALHAMBRA survey
astro-ph.CO
/ Authors
D. Cristobal-Hornillos, J. A. L. Aguerri, M. Moles, J. Perea, F. J. Castander, T. Broadhurst, E. J. Alfaro, N. Benitez, J. Cabrera, J. Cepa
and 12 more authors
M. Cervino, A. Fernandez-Soto, R. M. Gonzalez-Delgado, C. Husillos, L. Infante, I. Marquez, V. J. Martinez, J. Masegosa, A. del Olmo, F. Prada, J. M. Quintana, S. F. Sanchez
/ Abstract
The ALHAMBRA survey aims to cover 4 square degrees using a system of 20 contiguous, equal width, medium-band filters spanning the range 3500 A to 9700 A plus the standard JHKs filters. Here we analyze deep near-IR number counts of one of our fields (ALH08) for which we have a relatively large area (0.5 square degrees) and faint photometry (J=22.4, H=21.3 and K=20.0 at the 50% of recovery efficiency for point-like sources). We find that the logarithmic gradient of the galaxy counts undergoes a distinct change to a flatter slope in each band: from 0.44 at [17.0, 18.5] to 0.34 at [19.5, 22.0] for the J band; for the H band 0.46 at [15.5, 18.0] to 0.36 at [19.0, 21.0], and in Ks the change is from 0.53 in the range [15.0, 17.0] to 0.33 in the interval [18.0, 20.0]. These observations together with faint optical counts are used to constrain models that include density and luminosity evolution of the local type-dependent luminosity functions. Our models imply a decline in the space density of evolved early-type galaxies with increasing redshift, such that only 30% - 50% of the bulk of the present day red-ellipticals was already in place at z~1.