Pavo: Stellar feedback in action in a low-mass dwarf galaxy

TL;DR

This study uses MeerKAT observations to analyze the neutral hydrogen gas in the extremely low-mass, isolated dwarf galaxy Pavo, revealing a highly disturbed HI reservoir likely shaped by internal stellar feedback after a star formation event.

Contribution

First detailed HI study of the lowest mass isolated galaxy Pavo, showing feedback effects on its gas reservoir consistent with simulations.

Findings

Pavo's HI mass is the lowest known in an isolated galaxy.

Its HI reservoir is highly disturbed and offset from the stellar body.

The galaxy's HI properties align with predictions of feedback-driven disruption.

Abstract

MeerKAT observations of the recently discovered, extremely low mass galaxy, Pavo, have revealed a neutral gas (HI) reservoir that was undetected in archival HI single dish data. We measure Pavo's HI mass as $\log M_\mathrm{HI}/\mathrm{M_\odot} = 5.79 \pm 0.05$, making it the lowest mass HI reservoir currently known in an isolated galaxy (with a robust distance measurement). Despite Pavo's extreme isolation, with no known neighbor within over 700 kpc, its HI reservoir is highly disturbed. It does not show clear signs of rotation and its center of mass is offset from the stellar body center by 320 pc, while its peak is offset by 82 pc (both in projection). Despite this disturbed morphology, Pavo still appears to be consistent with the HI size--mass relation, although it is not possible to accurately determine a suitable inclination correction. Such disturbed, offset and disorganized HI reservoirs are predicted by simulations of low-mass, star-forming dwarfs in which supernova-driven outflows efficiently disrupt the interstellar medium after a star formation event. It is likely that we are witnessing Pavo in precisely this period, tens to a few hundred Myr after a star formation episode, when internal feedback has disrupted its gas reservoir.