Building the Stellar Halo Through Feedback in Dwarf Galaxies

TL;DR

This paper introduces a model where stellar feedback-driven gas motions in dwarf galaxies cause stars and clusters to migrate outward, forming stellar halos without external processes, and demonstrates this with simulations.

Contribution

The study presents a novel mechanism for stellar halo formation in dwarf galaxies driven by feedback-induced potential fluctuations, supported by simulation results.

Findings

Stars and clusters migrate from the center to the halo due to feedback effects.

The process can produce older, metal-poor stellar spheroids without outside-in formation.

Globular clusters can form in the ISM and migrate outward within 100 Myr.

Abstract

We present a new model for the formation of stellar halos in dwarf galaxies. We demonstrate that the stars and star clusters that form naturally in the inner regions of dwarfs are expected to migrate from the gas rich, star forming centre to join the stellar spheroid. For dwarf galaxies, this process could be the dominant source of halo stars. The effect is caused by stellar feedback-driven bulk motions of dense gas which, by causing potential fluctuations in the inner regions of the halo, couple to all collisionless components. This effect has been demonstrated to generate cores in otherwise cuspy cold dark matter profiles and is particularly effective in dwarf galaxy haloes. It can build a stellar spheroid with larger ages and lower metallicities at greater radii without requiring an outside-in formation model. Globular cluster-type star clusters can be created in the galactic ISM and then migrate to the spheroid on 100\thinspace Myr timescales. Once outside the inner regions they are less susceptible to tidal disruption and are thus long lived; clusters on wider orbits may be easily unbound from the dwarf to join the halo of a larger galaxy during a merger. A simulated dwarf galaxy ($\text{M}_{vir}\simeq10^{9}\text{M}_{\odot}$ at $z=5$) is used to examine this gravitational coupling to dark matter and stars.