Interaction between the IGM and a dwarf galaxy

TL;DR

This paper models the interaction between the intergalactic medium and dwarf irregular galaxies, providing a theoretical framework to estimate flow Mach numbers and compare with observations and simulations.

Contribution

It introduces a weak-shock plasmon model for dwarf galaxy-IGM interaction, linking theoretical predictions with observational data.

Findings

Model matches observed HI cloud shapes around dwarf galaxies.

Allows estimation of Mach number of IGM flow impacting dwarf galaxies.

Provides a theoretical basis for understanding gas-loss mechanisms in dwarf irregulars.

Abstract

Dwarf Galaxies are the most common objects in the Universe and are believed to contain large amounts of dark matter. There are mainly three morphologic types of dwarf galaxies: dwarf ellipticals, dwarf spheroidals and dwarf irregulars. Dwarf irregular galaxies are particularly interesting in dwarf galaxy evolution, since dwarf spheroidal predecessors could have been very similar to them. Therefore, a mechanism linked to gas-loss in dwarf irregulars should be observed, i.e. ram pressure stripping. In this paper, we study the interaction between the ISM of a dwarf galaxy, and a flowing IGM. We derive the weak-shock, plasmon solution corresponding to the balance between the post-bow shock pressure and the pressure of the stratified ISM (which we assume follows the fixed stratification of a gravitationally dominant dark matter halo). We compare our model with previously published numerical simulations and with the observed shape of the HI cloud around the Ho II and Pegasus dwarf irregular galaxies. We show that such a comparison provides a straightforward way for estimating the Mach number of the impinging flow.