Beyond UVJ: Color Selection of Galaxies in the JWST Era

Jacqueline Antwi-Danso, Casey Papovich, Joel Leja, Danilo Marchesini, Z. Cemile Marsan, Nicholas S. Martis, Ivo Labbé, Adam Muzzin, Karl Glazebrook, Caroline M.S. Straatman, Kim Vy H. Tran

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

We present a new rest-frame color-color selection method using synthetic u s − g s and g s − i s, (ugi)s colors to identify star-forming and quiescent galaxies. Our method is similar to the widely used U − V versus V − J (UVJ) diagram. However, UVJ suffers known systematics. Spectroscopic campaigns have shown that UVJ-selected quiescent samples at z ≳ 3 include ∼10%-30% contamination from galaxies with dust-obscured star formation and strong emission lines. Moreover, at z > 3, UVJ colors are extrapolated because the rest-frame band shifts beyond the coverage of the deepest bandpasses at <5 μm (typically Spitzer/IRAC 4.5 μm or future JWST/NIRCam observations). We demonstrate that (ugi)s offers improvements to UVJ at z > 3, and can be applied to galaxies in the JWST era. We apply (ugi)s selection to galaxies at 0.5 < z < 6 from the (observed) 3D-HST and UltraVISTA catalogs, and to the (simulated) JAGUAR catalogs. We show that extrapolation can affect (V − J)0 color by up to 1 mag, but changes ( g s − i s ) 0 color by ≤0.2 mag, even at z ≃ 6. While (ugi)s-selected quiescent samples are comparable to UVJ in completeness (both achieve ∼85%-90% at z = 3-3.5), (ugi)s reduces contamination in quiescent samples by nearly a factor of 2, from ≃35% to ≃17% at z = 3, and from ≃60% to ≃33% at z = 6. This leads to improvements in the true-to-false-positive ratio (TP/FP), where we find TP/FP ≳2.2 for (ugi)s at z ≃ 3.5 − 6, compared to TP/FP < 1 for UVJ-selected samples. This indicates that contaminants will outnumber true quiescent galaxies in UVJ at these redshifts, while (ugi)s will provide higher-fidelity samples.

Original languageEnglish (US)
Article number166
JournalAstrophysical Journal
Volume943
Issue number2
DOIs
StatePublished - Feb 1 2023

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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