The COSMOS-WIRCam near-infrared imaging survey: I: BzK selected passive and star forming galaxy candidates at z>1.4

TL;DR

This paper presents a comprehensive near-infrared survey of the COSMOS field, identifying and analyzing a large sample of BzK-selected galaxies at z>1.4, providing insights into galaxy formation and clustering at high redshift.

Contribution

It offers the largest secure sample of BzK-selected passive and star-forming galaxies at z>1.4, with detailed clustering analysis and comparison to galaxy formation models.

Findings

Quiescent galaxy counts exceed model predictions.

Passive BzK galaxies show strong small-scale clustering.

Sample includes 3931 quiescent and 25,757 star-forming galaxies at z~2.

Abstract

(abridged) We present a new near-infrared survey covering the 2 deg sq COSMOS field. Combining our survey with Subaru B and z images we construct a deep, wide-field optical-infrared catalogue. At Ks<23 (AB magnitudes) our survey completeness is greater than 90% and 70% for stars and galaxies respectively and contains 143,466 galaxies and 13,254 stars. At z~2 our catalogues contain 3931 quiescent and 25,757 star-forming BzK-selected galaxies representing the largest and most secure sample of these objects to date. Our counts of quiescent galaxies turns over at Ks~22 an effect which we demonstrate cannot be due to sample incompleteness. In our survey both the number of faint and bright quiescent objects exceeds the predictions of a semi-analytic galaxy formation model, indicating potentially the need for further refinements in the amount of merging and AGN feedback at z~2 in these models. We measure the angular correlation function for each sample and find that at small scales the correlation function for passive BzK galaxies exceeds the clustering of dark matter. We use 30-band photometric redshifts to derive the spatial correlation length and the redshift distributions for each object class. At Ks<22 we find r_0^{\gamma/1.8}=7.0 +/-0.5h^{-1} Mpc for the passive BzK candidates and 4.7+/-0.8h^{-1} Mpc for the star-forming BzK galaxies. Our pBzK galaxies have an average photometric redshift of z_p~1.4, in approximate agreement with the limited spectroscopic information currently available. The stacked Ks image will be made publicly available from IRSA.