On the neutral gas content of nine new Milky Way satellite galaxy candidates

TL;DR

This study searches for neutral hydrogen in nine newly discovered ultra-faint Milky Way satellite galaxy candidates using an improved HI survey, finding no detections and suggesting these galaxies are HI deficient due to environmental effects.

Contribution

It provides the first upper limits on HI content for these nine new satellite candidates, supporting theories of gas removal by tidal and ram-pressure forces.

Findings

No HI emission detected from the candidates.

Upper limits suggest some are HI deficient.

Supports environmental gas removal in satellite galaxies.

Abstract

We use a new, improved version of the HI Parkes All-Sky Survey to search for HI emission from nine new, ultra-faint Milky Way satellite galaxy candidates recently discovered in data from the Dark Energy Survey. None of the candidates is detected in HI, implying upper limits for their HI masses of typically several hundred to a few thousand solar masses. The resulting upper limits on M_HI / L_V and M_HI / M_star suggest that at least some of the new galaxy candidates are HI deficient. This finding is consistent with the general HI deficiency of satellite galaxies located within the Milky Way's virial radius and supports the hypothesis that gas is being removed from satellites by tidal and ram-pressure forces during perigalactic passages. In addition, some of the objects may be embedded in, and interacting with, the extended neutral and ionised gas filaments of the Magellanic Stream.