Ram pressure stripping of an isolated Local Group dwarf galaxy: evidence for an intra-group medium

TL;DR

This study presents evidence of ram pressure stripping in the isolated Local Group dwarf galaxy Pegasus, indicating the presence of an intra-group medium with specific density levels.

Contribution

First observation of ram pressure stripping morphology in an isolated Local Group galaxy, providing evidence for intra-group medium existence.

Findings

Pegasus exhibits cometary HI morphology indicative of ram pressure stripping.

The intra-group medium density is estimated to be between 10^{-5} and 10^{-6} cm^{-3}.

This is the first evidence of intra-group medium affecting an isolated galaxy in the Local Group.

Abstract

We compare the stellar structure of the isolated, Local Group dwarf galaxy Pegasus (DDO216) with low resolution HI maps from Young et al. (2003). Our comparison reveals that Pegasus displays the characteristic morphology of ram pressure stripping; in particular, the HI has a ``cometary'' appearance which is not reflected in the regular, elliptical distribution of the stars. This is the first time this phenomenon has been observed in an isolated Local Group galaxy. The density of the medium required to ram pressure strip Pegasus is at least $10^{-5} - 10^{-6}$, cm$^{-3}$. We conclude that this is strong evidence for an inter-galactic medium associated with the Local Group.