Improved SED-Fitting Assumptions Result in Inside-Out Quenching at $z\sim0.5$ and Quenching at All Radii Simultaneously at $z\sim1$

TL;DR

This study shows that using more realistic priors in SED fitting reveals that galaxies at higher redshifts quench uniformly across all radii, while at lower redshifts they quench from the inside-out, challenging previous assumptions.

Contribution

The paper introduces physically motivated priors in SED fitting, improving the accuracy of star formation and dust profiles, and revises the understanding of galaxy quenching patterns over cosmic time.

Findings

At $z ext{~}1.3$, galaxies quench uniformly across radii.

At $z ext{~}0.5$, galaxies quench from the inside-out.

Physically motivated priors improve SED fitting accuracy.

Abstract

Many studies conclude that galaxies quench from the inside-out by examining profiles of specific star-formation rate (sSFR). These are usually measured by fitting spectral energy distributions (SEDs) assuming a fixed dust law and uniform priors on all parameters. Here, we examine the effects of more physically motivated priors: a flexible dust law, an exponential prior on the dust attenuation $A_V$, and Gaussian priors that favor extended star-formation histories. This results in model colors that better trace observations. We then perform radial SED fits to multiband flux profiles measured from Hubble Space Telescope images for 1,440 galaxies at $0.4<z<1.5$ of stellar masses $10^{10}-10^{11.5}\ M_{\odot}$ using both the traditional and the more physically motivated assumptions. The latter results in star formation rate and $A_V$ profiles that agree with measurements from spectroscopy and $A_V$ profiles that behave correctly as a function of inclination. Since green valley galaxies at $z\sim1.3$ are expected to evolve into quiescent galaxies at $z\sim0.9$, we compare their sSFR profiles using the more physically motivated assumptions. Their slopes are similar at all masses ($0.06 - 0.08~\textrm{dex}~\textrm{kpc}^{-1}$), and the normalizations for the quiescent galaxies are lower. Therefore, the sSFR profiles decline with time as quenching occurs at all radii simultaneously. We compare profiles of green valley galaxies at $z\sim0.9$ and quiescent galaxies at $z\sim0.5$. The former are shallower at all masses by $\sim0.1~\textrm{dex}~\textrm{kpc}^{-1}$. The sSFR profiles steepen with time as galaxies quench from the inside-out. In summary, at $z\sim0.9-1.3$, galaxies quench at all radii simultaneously, and at $z\sim0.5-0.9$, they quench from the inside-out.