Wandering Stars: an Origin of Escaped Populations

TL;DR

This paper proposes that stars can be ejected or become wandering within galaxy halos due to gravitational impulses during satellite galaxy interactions, with implications for observable populations and galaxy formation history.

Contribution

It introduces a mechanism for the creation of escaped and wandering stars through gravitational impulses during satellite galaxy passages, linking these populations to galaxy merger histories.

Findings

Wandering stars can be observed via classical novae and SNIa.

Large satellites and radial orbits produce most ejected stars.

These populations provide insights into galaxy merging histories.

Abstract

We demonstrate that stars beyond the virial radii of galaxies may be generated by the gravitational impulse received by a satellite as it passes through the pericenter of its orbit around its parent. These stars may become energetically unbound (escaped stars), or may travel to further than a few virial radii for longer than a few Gyr, but still remain energetically bound to the system (wandering stars). Larger satellites (10-100% the mass of the parent), and satellites on more radial orbits are responsible for the majority of this ejected population. Wandering stars could be observable on Mpc scales via classical novae, and on 100 Mpc scales via SNIa. The existence of such stars would imply a corresponding population of barely-bound, old, high velocity stars orbiting the Milky Way, generated by the same physical mechanism during the Galaxy's formation epoch. Sizes and properties of these combined populations should place some constraints on the orbits and masses of the progenitor objects from which they came, providing insight into the merging histories of galaxies in general and the Milky Way in particular.