Pavo: Stellar Feedback in Action in a Low-mass Dwarf Galaxy

MeerKAT observations of the recently discovered, extremely low mass galaxy Pavo have revealed a neutral gas (H i ) reservoir that was undetected in archival H i single dish data. We measure Pavo’s H i mass as log M HI / M ⊙ = 5.79 ± 0.05 , making it the lowest mass H i 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 H i 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 H i size–mass relation, although it is not possible to accurately determine a suitable inclination correction. Such disturbed, offset, and disorganized H i 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 (SF) event. It is likely that we are witnessing Pavo in precisely this period, tens to a few hundred Myr after a SF episode, when internal feedback has disrupted its gas reservoir.