Beyond UVJ: Color Selection of Galaxies in the JWST Era

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.

Probing the Stellar Populations and Star Formation History of Early-type Galaxies at 0 < z < 1.1 in the Rest-frame Ultraviolet

“…It is also not possible to push z form much higher than 10 as the value of τ appears to plateau at this redshift (Figure 8) and we would start to push past the epoch of reionization. As such, our results suggest that the average M * cluster ETG realistically formed between z form = 3 and 10 (corresponding to a range in time of about 1.5 Gyr), with efolding timescales of τ = 0.35-0.7 Gyr, meaning that the vast majority of stars in these galaxies formed rapidly at high redshift and the galaxies became passive thereafter-consistent with some of the high-redshift quiescent galaxies now observed with JWST (Nanayakkara et al 2022;Antwi-Danso et al 2023;Glazebrook et al 2023;Looser et al 2023;Strait et al 2023). The results are also in general agreement with optical studies of massive quiescent galaxies at intermediate to high redshifts, where such galaxies are found to have started forming their stars at z form = 5-10 (Tacchella et al 2022) with timescales shorter than 1 Gyr, and the peak of star formation activity potentially occurring at z ∼ 2.3-3.5 (Onodera et al 2015;D'Eugenio et al 2021).…”

An Atlas of Color-selected Quiescent Galaxies at z > 3 in Public JWST Fields

“…In parallel, we follow the novel method described in Gould et al (2023; see also Antwi-Danso et al 2023 for an alternative approach introducing a synthetic band). The authors incorporate the NUV magnitude in their selection and model the galaxy distribution in the (NUV − U, U − V, V − J) space with a minimal number of Gaussians carrying information (Gaussian mixture model (GMM); Pedregosa et al 2011).…”

The Heavy Metal Survey: Star Formation Constraints and Dynamical Masses of 21 Massive Quiescent Galaxies at z = 1.3–2.3

“…With the advent of more efficient near-IR spectrographs such as X-Shooter (VLT; Vernet et al 2011), KMOS (VLT; Sharples et al 2013), and MOSFIRE (Keck Observatory;McLean et al 2012), spectroscopic redshifts, robust velocity dispersion measurements, and dynamical mass estimates became available for substantial samples or stacks of distant quiescent galaxies (e.g., van de Sande et al 2011Bezanson et al 2013;Belli et al 2014Belli et al , 2017bLonoce et al 2015;Mendel et al 2015;Onodera et al 2015;Saracco et al 2019;Carnall et al 2022;Park et al 2023;Zhuang et al 2023). In recent years, spectroscopic studies have pushed to even higher redshifts (z > 3; e.g., Glazebrook et al 2017;Schreiber et al 2018;Tanaka et al 2019;Forrest et al 2020;Esdaile et al 2021;Antwi-Danso et al 2023;Carnall et al 2023). At the same time, deeper observations have enabled the first measurements of chemical abundances and resolved stellar kinematics at z > 2.…”