You Are What You Eat: The Circumgalactic Medium Around BreakBRD Galaxies has Low Mass and Angular Momentum

TL;DR

This study investigates the circumgalactic medium of breakBRD galaxies, revealing they have less gas, lower angular momentum, and higher metallicity in their halos, indicating limited gas accretion and disk feeding.

Contribution

It provides the first detailed analysis of the circumgalactic medium properties of breakBRD galaxies, linking halo gas characteristics to their unique star formation patterns.

Findings

BreakBRD galaxies have less circumgalactic gas than similar mass galaxies.

Their halo gas shows lower angular momentum and more misalignment.

The circumgalactic medium is more metal-rich in breakBRD galaxies.

Abstract

Observed breakBRD ("break bulges in red disks") galaxies are a nearby sample of face-on disk galaxies with particularly centrally-concentrated star formation: they have red disks but recent star formation in their centers as measured by the D$_n$4000 spectral index. In Kopenhafer et al. (2020), a comparable population of breakBRD analogues was identified in the TNG simulation, in which the central concentration of star formation was found to reflect a central concentration of dense, starforming gas caused by a lack of dense gas in the galaxy outskirts. In this paper we examine the circumgalactic medium of the central breakBRD analogues to determine if the extended halo gas also shows differences from that around comparison galaxies with comparable stellar mass. We examine the circumgalactic medium gas mass, specific angular momentum, and metallicity in these galaxy populations. We find less gas in the circumgalactic medium of breakBRD galaxies, and that the breakBRD circumgalactic medium is slightly more concentrated than that of comparable stellar mass galaxies. In addition, we find that the angular momentum in the circumgalactic medium of breakBRD galaxies tends to be low for their stellar mass, and show more misalignment to the angular momentum vector of the stellar disk. Finally, we find that the circumgalactic medium metallicity of breakBRD galaxies tends to be high for their stellar mass. Together with their low SFR, we argue that these CGM properties indicate a small amount of disk feeding concentrated in the central regions, and a lack of low-metallicity gas accretion from the intergalactic medium.