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

doi:10.3847/1538-4357/aca294

paper

Beyond UVJ: Color Selection of Galaxies in the JWST Era

arXiv:2207.07170 · doi:10.3847/1538-4357/aca294

Abstract

We present a new rest-frame color-color selection method using "synthetic $u_{s} - g_{s}$ and $g_{s} - i_{s}$ '', $(ug i)_{s}$ colors to identify star-forming and quiescent galaxies. Our method is similar to the widely-used $U - V$ versus $V - J$ ( $U V J$ ) diagram. However, $U V J$ suffers known systematics. Spectroscopic campaigns have shown that $U V J$ -selected quiescent samples at $z ≳ 3$ include $\sim 10 - 30%$ contamination from galaxies with dust-obscured star formation and strong emission lines. Moreover, at $z > 3$ , $U V J$ colors are extrapolated because the rest-frame J-band shifts beyond the coverage of the deepest bandpasses at $< 5 μ m$ (typically $S p i t z er$ /IRAC 4.5 $μ m$ or future $J W S T$ /NIRCam observations). We demonstrate that $(ug i)_{s}$ offers improvements to $U V J$ at $z > 3$ , and can be applied to galaxies in the $J W S T$ era. We apply $(ug i)_{s}$ 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 magnitude, but changes $(u_{s} - g_{s})_{0}$ color by $\leq$ 0.2 mag, even at $z ≃ 6$ . While $(ug i)_{s}$ -selected quiescent samples are comparable to $U V J$ in completeness (both achieve $\sim$ 85-90% at $z = 3 - 3.5$ ), $(ug i)_{s}$ reduces contamination in quiescent samples by nearly a factor of two, 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 $(ug i)_{s}$ at $z ≃ 3.5 - 6$ , compared to TP/FP $<$ 1 for $U V J$ -selected samples. This indicates that contaminants will outnumber true quiescent galaxies in $U V J$ at these redshifts, while $(ug i)_{s}$ will provide higher-fidelity samples.

33 pages, 20 figures, accepted for publication in ApJ

Beyond UVJ: Color Selection of Galaxies in the JWST Era

Abstract

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