JWST/NIRSpec spectroscopy of intermediate-mass quiescent galaxies at $z \sim 3-4$

TL;DR

This study uses JWST/NIRSpec spectroscopy to analyze three intermediate-mass quiescent galaxies at redshifts 3-4, revealing their properties, morphology, and potential quenching mechanisms, contributing new insights into early galaxy evolution.

Contribution

First spectroscopic confirmation of low-mass quiescent galaxies at z~3-4 with detailed morphological and emission line analysis, highlighting possible AGN-driven quenching.

Findings

Galaxies are consistent with quiescent population with low sSFR.

One galaxy shows disc-like morphology with Sersic index ~1.1.

Quenching timescales are less than 1 Gyr, possibly due to AGN feedback.

Abstract

We present the analysis of three intermediate-mass quiescent galaxies (QGs) with stellar masses of $\sim10^{10}M_{\rm \odot}$ at redshifts $z\sim 3 - 4$ using NIRSpec low-resolution spectroscopy. Utilising the SED fitting code BAGPIPES, we confirm these target galaxies are consistent with quiescent population, with their specific star formation rates (sSFR) falling below 2-dex the star-forming main sequence at the same redshifts. Additionally, we identify these QGs to be less massive than those discovered in previous works, particularly prior to the JWST era. Two of our target galaxies exhibit the potentially-blended H${\alpha}$+[NII] emission line within their spectra with $S/N>5$. We discuss whether this feature comes from an Active Galactic Nucleus (AGN) or star formation although future high-resolution spectroscopy is required to reach a conclusion. One of the target galaxies is covered by JWST/NIRCam imaging of the PRIMER survey. Using the 2D profile fitting code Galfit, we examine its morphology, revealing a disc-like profile with a S\'{e}rsic index of $n=1.1 \pm 0.1$. On the size-mass relation, we find a potential distinction between less-massive ($\log_{10}{(M_*/M_\odot)}<10.3$) and massive ($\log_{10}{(M_*/M_\odot)}>10.3$) QGs in their evolutionary pathways. The derived quenching timescales for our targets are less than 1 Gyr. This may result from these galaxies being quenched by AGN feedback, supporting the AGN scenario of the emission line features.