CLEAR: The Morphological Evolution of Galaxies in the Green Valley

Abstract

Quiescent galaxies having more compact morphologies than star-forming galaxies has been a consistent result in the field of galaxy evolution. What is not clear is at what point this divergence happens, i.e., when do quiescent galaxies become compact, and how big of a role does the progenitor effect play in this result? Here we aim to model the morphological and star formation histories of high-redshift (0.8 < z < 1.65) massive galaxies ( log ( M / M ⊙ ) > 10.2) with stellar population fits using Hubble Space Telescope/WFC3 G102 and G141 grism spectra plus photometry from the CANDELS Lyα Emission at Reionization (CLEAR) survey, constraining the star formation histories for a sample of ∼400 massive galaxies using flexible star formation histories. We develop a novel approach to classifying galaxies by their star formation activity in a way that highlights the green valley population, by modeling the specific star formation rate distributions as a function of redshift and deriving the probability that a galaxy is quiescent (P Q ). Using P Q and our flexible star formation histories we outline the evolutionary paths of our galaxies in relation to stellar mass, Sérsic index, effective radius R eff, and stellar mass surface density. We find that the galaxies show no appreciable stellar mass growth after entering the green valley (a net decrease of 4%) while their stellar mass surface densities increase by ∼0.25 dex. Therefore galaxies are becoming compact during the green valley and this is due to an increase in the Sérsic index and a decrease in R eff.

The MUSE Ultra Deep Field (MUDF). V. Characterizing the Mass–Metallicity Relation for Low-mass Galaxies at z ∼ 1–2

“…Significant progress has been made in this area with large slitless spectroscopic surveys using the near-infrared capabilities of the Wide Field Camera 3 (WFC3) on board the Hubble Space Telescope (HST). The G102 and G140 grism dispersing elements provide continuous wavelength coverage from 0.8-1.7 μm at low spectral resolution, enabling the characterization of rest-frame optical diagnostic emission lines up to z ≈ 3 (e.g., Atek et al 2010;Brammer et al 2012;Momcheva et al 2016;Pharo et al 2019;Simons et al 2021;Mowla et al 2022;Papovich et al 2022;Estrada-Carpenter et al 2023;Revalski et al 2023;Simons et al 2023;Stephenson et al 2024). Recently, the MZR was expanded by Henry et al (2021) down to the lowest masses characterized at these redshifts, reaching log(M å /M e ) ≈ 8.3 at z ≈ 1-2.…”