Beyond UVJ: Color Selection of Galaxies in the JWST Era
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AbstractWe present a new rest-frame colorcolor selection method using synthetic usgs and gsis, (ugi)s colors to identify star-forming and quiescent galaxies. Our method is similar to the widely used UV versus VJ (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 m (typically Spitzer/IRAC 4.5 m 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 (VJ)0 color by up to 1 mag, but changes (gsis)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 = 33.5), (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.
