Substructure and Tidal Streams in the Andromeda Galaxy and its Satellites

TL;DR

This paper reviews the discovery and analysis of tidal streams in the Andromeda galaxy and its satellites, highlighting their significance in understanding galaxy formation and accretion history.

Contribution

It provides a comprehensive overview of tidal streams in M31 and its satellites, emphasizing recent discoveries and their implications for galaxy evolution.

Findings

Most of M31's inner halo debris is linked to a major accretion event.

Many outer halo globular clusters are associated with tidal streams.

Tidal features are also observed around M33, M32, NGC 205, and NGC 147.

Abstract

Tidal streams from existing and destroyed satellite galaxies populate the outer regions of the Andromeda galaxy (M31). This inhomogeneous debris can be studied without many of the obstacles that plague Milky Way research. We review the history of tidal stream research in M31, and in its main satellite galaxies. We highlight the numerous tidal streams observed around M31, some of which reside at projected distances of up to 120 kpc from the center of this galaxy. Most notable is the Giant Stellar Stream, a signature of the most recent significant accretion event in the M31 system. This event involved an early-type progenitor of ~10^9 solar masses that came within a few kpc of M31's center roughly a gigayear ago; almost all of the inner halo debris (within 50 kpc) in M31 can be tied either directly or indirectly to this event. We draw attention to the fact that most of M31's outer halo globular clusters lie preferentially on tidal streams and discuss the potential this offers to use these systems as probes of the accretion history. Tidal features observed around M33, M32, NGC 205 and NGC 147 are also reviewed. We conclude by discussing future prospects for this field.