Gas depletion in Local Group dwarfs on ~250 kpc scales: Ram pressure stripping assisted by internal heating at early times

TL;DR

This study models how early star formation heats dwarf galaxy gas, making it easier for host galaxy halos to strip the gas, explaining the observed distribution of gas-deficient dwarfs within 270 kpc.

Contribution

It introduces an analytical model showing early internal heating facilitates gas removal in dwarfs, accounting for their gas deficiency at large galactocentric distances.

Findings

Early star formation heats gas, enabling stripping by host halos.

Model reproduces observed distribution of gas-rich and gas-deficient dwarfs.

Gas removal occurs if dwarfs fell in at high redshifts (z~3-10).

Abstract

A recent survey of the Galaxy and M31 reveals that more than 90% of dwarf galaxies within 270 kpc of their host galaxy are deficient in HI gas. At such an extreme radius, the coronal halo gas is an order of magnitude too low to remove HI gas through ram-pressure stripping for any reasonable orbit distribution. However, all dwarfs are known to have an ancient stellar population (\geq 10 Gyr) from early epochs of vigorous star formation which, through heating of HI, could allow the hot halo to remove this gas. Our model looks at the evolution of these dwarf galaxies analytically as the host-galaxy dark matter halo and coronal halo gas builds up over cosmic time. The dwarf galaxies - treated as spherically symmetric, smooth distributions of dark matter and gas - experience early star formation, which sufficiently heats the gas allowing it to be removed easily through tidal stripping by the host galaxy, or ram-pressure stripping by a tenuous hot halo (n_H = 3x10^{-4} cm^{-3} at 50 kpc). This model of evolution is able to explain the observed radial distribution of gas-deficient and gas-rich dwarfs around the Galaxy and M31 if the dwarfs fell in at high redshifts (z~3-10).