Uncovering the MIR emission of quiescent galaxies with $JWST$

TL;DR

This study uses JWST imaging to analyze the mid-IR emission of quiescent galaxies beyond the local universe, revealing diverse MIR spectra and potential PAH features, and creating a comprehensive UV-to-radio SED template.

Contribution

It provides the first detailed MIR spectral analysis of intermediate-redshift quiescent galaxies and develops a panchromatic SED template for future interstellar medium studies.

Findings

Quiescent galaxies show a range of MIR spectra with stellar and dust components.

Presence of PAH features suggests soft radiation fields in these galaxies.

The constructed UV-to-radio SED template aids future ISM research at high redshift.

Abstract

We present a study of the mid-IR (MIR) emission of quiescent galaxies (QGs) beyond the local universe. Using deep $JWST$ imaging in the SMACS-0723 cluster field we identify a mass limited ($M_{*} >10^{9}$M$_{\odot}$) sample of intermediate redshift QGs ($0.2<z<0.7$) and perform modeling of their rest-frame UV to MIR photometry. We find that QGs exhibit a range of MIR spectra that are composed of a stellar continuum and a dust component that is 1-2 orders of magnitude fainter to that of star-forming galaxies. The observed scatter in the MIR spectra, especially at $\lambda_{\rm rest} > 5 \mu$m, can be attributed to different dust continuum levels and/or the presence of Polycyclic Aromatic Hydrocarbons (PAHs) features. The latter would indicate enhanced 11.3- and 12.7 $\mu$m PAHs strengths with respect to those at 6.2- and 7.7$ \mu$m, consistent with the observed spectra of local ellipticals and indicative of soft radiation fields. Finally, we augment the average UV-to-MIR spectrum of the population with cold dust and gas emission in the far-IR/mm and construct a panchromatic UV-to-radio SED that can serve as a template for the future exploration of the interstellar medium of $z>0$ QGs with ALMA and $JWST$.