Detection of quiescent galaxies in a bicolor sequence from z=0-2

TL;DR

This study uses a novel photometric color selection method to identify and analyze quiescent and star-forming galaxies up to redshift 2, revealing their distinct properties, distribution, and clustering behavior, and suggesting a link to halo mass.

Contribution

Introduces a new rest-frame color selection technique to distinguish quiescent and star-forming galaxies in photometric data up to z~2, highlighting their bimodal distribution and clustering differences.

Findings

Bimodal galaxy populations observed up to z~2 in rest-frame color space.

Quiescent galaxies are more strongly clustered than star-forming ones.

Brightest galaxies at z=1-2 are roughly equally star-forming and quiescent.

Abstract

We investigate the properties of quiescent and star-forming galaxy populations to z~2 with purely photometric data, employing a novel rest-frame color selection technique. From the UKIDSS Ultra-Deep Survey Data Release 1, with matched optical and mid-IR photometry taken from the Subaru XMM Deep Survey and Spitzer Wide-Area Infrared Extragalactic Survey respectively, we construct a K-selected galaxy catalog and calculate photometric redshifts. Excluding stars, objects with uncertain z_phot solutions, those that fall in bad or incomplete survey regions, and those for which reliable rest-frame colors could not be derived, 30108 galaxies with K<22.4 (AB) and z<2.5 remain. The galaxies in this sample are found to occupy two distinct populations in the rest-frame U-V vs. V-J color space: a clump of red, quiescent galaxies (analogous to the red sequence) and a track of star-forming galaxies extending from blue to red U-V colors. This bimodal behavior is seen up to z~2. Due to a combination of measurement errors and passive evolution, the color-color diagram is not suitable to distinguish the galaxy bimodality at z>2 for this sample, but we show that MIPS 24um data suggest that a significant population of quiescent galaxies exists even at these higher redshifts. At z=1-2, the most luminous objects in the sample are divided roughly equally between star-forming and quiescent galaxies, while at lower redshifts most of the brightest galaxies are quiescent. Moreover, quiescent galaxies at these redshifts are clustered more strongly than those actively forming stars, indicating that galaxies with early-quenched star formation may occupy more massive host dark matter halos. This suggests that the end of star formation is associated with, and perhaps brought about by, a mechanism related to halo mass.