2002ApJ...570...54C

The Las Campanas Infrared Survey, based on broadband optical and near-infrared photometry, is designed to robustly identify a statistically significant and representative sample of evolved galaxies at redshifts z>1. We have completed an H-band imaging survey over 1.1 deg² of sky in six separate fields. The average 5 σ detection limit in a 4" diameter aperture is H∼20.8. Here we describe the design of the survey, the observation strategies, data-reduction techniques, and object identification procedures. We present sample near-infrared and optical photometric catalogs for objects identified in two survey fields. The optical images of the Hubble Deep Field-South region obtained from the literature reach 5 σ detection thresholds in a 4" diameter aperture of U∼24.6, B∼26.1, V∼25.6, R∼25.1, and I∼24.2 mag. The optical images of the Chandra Deep Field-South region obtained from our own observations reach 5 σ detection thresholds in a 4" diameter aperture of V∼26.8, R∼26.2, I∼25.3, and z'∼23.7 mag. We perform object detection in all bandpasses and identify ≳ 54,000 galaxies over 1408 arcmin² of sky in the two fields. Of these galaxies, ∼14,000 are detected in the H band and ∼2000 have the colors of evolved galaxies, I-H≳3, at z≳1. We find that (1) the differential number counts N(m) for the H-band-detected objects has a slope of dlogN(m)/dm=0.45±0.01 mag^–2 at H≲19 and 0.27±0.01 mag^–2 at H≳19, with a mean surface density ~7200 deg^–2 mag^–1 at H=19. In addition, we find that (2) the differential number counts for the H-band-detected red objects has a very steep slope, dlogN(m;I-H≳3)/dm=0.84±0.06 mag^–2 at H≲20 and 0.32±0.07 mag^–2 at H≳20, with a mean surface density ~3000 deg^–2 mag^–1 at H=20. Finally, we find that (3) galaxies with red optical to near-IR colors (I-H>3) constitute ~20% of the H-band-detected galaxies at H≲21, but only ~2% at H≲19. We show that red galaxies are strongly clustered, which results in a strong field-to-field variation in their surface density. Comparisons of observations and predictions based on various formation scenarios indicate that these red galaxies are consistent with mildly evolving early-type galaxies at z∼1, although with a significant amount of ongoing star formation, as indicated by the large scatter in their V-I colors.