A Break In the Size-Stellar Mass Relation: Evidence for Quenching and Feedback in Dwarf Galaxies

TL;DR

This study compares stellar and gaseous extents in nearby galaxies, revealing a size relation break at low masses and evidence of environmental effects like quenching in dwarf galaxies.

Contribution

It introduces a new analysis of stellar and HI size relations across a broad galaxy mass range, highlighting a break at low masses and environmental impacts on dwarf galaxies.

Findings

Dwarf galaxies in clusters show reduced HI near stellar edges due to environmental quenching.

A break in the stellar size-mass relation occurs at around 4×10^8 solar masses.

Field dwarf galaxies exhibit larger stellar-to-HI size ratios, consistent with feedback effects.

Abstract

Mapping stars and gas in nearby galaxies is fundamental for understanding their growth and the impact of their environment. This issue is addressed by comparing the stellar "edges" of galaxies $D_{\rm stellar}$, defined as the outermost diameter where in situ star formation significantly drops, with the gaseous distribution parameterized by the neutral atomic hydrogen diameter measured at 1 $M_{sun}$/pc$^2$, $D_{HI}$. By sampling a broad HI mass range $10^5 M_{sun} < M_{HI} < 10^{11} M_{sun}$, we find several dwarf galaxies with $M_{HI} < 10^9 M_{sun}$ from the field and Fornax Cluster which are distinguished by $D_{\rm stellar} >> D_{HI}$. For the cluster dwarfs, the average HI surface density near $D_{\rm stellar}$ is $\sim$0.3 $M_{sun}$/pc$^2$, reflecting the impact of quenching and outside-in gas removal from ram pressure and tidal interactions. In comparison, $D_{\rm stellar}/D_{HI}$ ranges between 0.5-2 in dwarf field galaxies, consistent with the expectations from stellar feedback. Only more massive disk galaxies in the field can thus be characterized by the common assumption that $D_{\rm stellar} \lesssim D_{HI}$. We discover a break in the $D_{\rm stellar}-M_{\rm stellar}$ relation at $m_{break} \sim 4\times10^8 M_{sun}$ that potentially differentiates the low mass regime where the influence of stellar feedback and environmental processes more prominently regulates the sizes of nearby galaxies. Our results highlight the importance of combining deep optical and HI imaging for understanding galaxy evolution.