Demographics of Star-forming Galaxies since $z\sim2.5$. I. The $UVJ$ Diagram in CANDELS

Jerome J. Fang, S. M. Faber, David C. Koo, Aldo Rodriguez-Puebla, Yicheng Guo, Guillermo Barro, Peter Behroozi, Gabriel Brammer, Zhu Chen, Avishai Dekel, Henry C. Ferguson, Eric Gawiser, Mauro Giavalisco, Jeyhan Kartaltepe, Dale D. Kocevski, Anton M. Koekemoer, Elizabeth J. McGrath, Daniel McIntosh, Jeffrey A. Newman, Camilla Pacifici, Viraj Pandya, Pablo G. Perez-Gonzalez, Joel R. Primack, Brett Salmon, Jonathan R. Trump, Benjamin Weiner, S. P. Willner, Viviana Acquaviva, Tomas Dahlen, Steven L. Finkelstein, Kristian Finlator, Adriano Fontana, Audrey Galametz, Norman A. Grogin, Ruth Gruetzbauch, Seth Johnson, Bahram Mobasher, Casey J. Papovich, Janine Pforr, Mara Salvato, P. Santini, Arjen van der Wel, Tommy Wiklind, Stijn Wuyts

Published 2017-10-16Version 1

This is the first in a series of papers examining the demographics of star-forming galaxies at $0.2<z<2.5$ in CANDELS. We study 9,100 galaxies from GOODS-S and UDS having published values of redshifts, masses, star-formation rates (SFRs), and dust attenuation ($A_V$) derived from UV-optical SED fitting. In agreement with previous works, we find that the $UVJ$ colors of a galaxy are closely correlated with its specific star-formation rate (SSFR) and $A_V$. We define rotated $UVJ$ coordinate axes, termed $S_\mathrm{SED}$ and $C_\mathrm{SED}$, that are parallel and perpendicular to the star-forming sequence and derive a quantitative calibration that predicts SSFR from $C_\mathrm{SED}$ with an accuracy of ~0.2 dex. SFRs from UV-optical fitting and from UV+IR values based on Spitzer/MIPS 24 $\mu\mathrm{m}$ agree well overall, but systematic differences of order 0.2 dex exist at high and low redshifts. A novel plotting scheme conveys the evolution of multiple galaxy properties simultaneously, and dust growth, as well as star-formation decline and quenching, exhibit "mass-accelerated evolution" ("downsizing"). A population of transition galaxies below the star-forming main sequence is identified. These objects are located between star-forming and quiescent galaxies in $UVJ$ space and have lower $A_V$ and smaller radii than galaxies on the main sequence. Their properties are consistent with their being in transit between the two regions. The relative numbers of quenched, transition, and star-forming galaxies are given as a function of mass and redshift.