Published in "Tidal Streams in the Local Group and Beyond", Astrophysics and Space Science Library, Volume 420. ISBN 978-3-319-19335-9. Springer International Publishing Switzerland, 2016, p. 219.
http://arxiv.org/abs/1603.04656

For a PDF version of the article, click here.

STELLAR TIDAL STREAMS IN EXTERNAL GALAXIES

Jeffrey L. Carlin 1, Rachael L. Beaton 2, David Martinez-Delgado 3 and R. Jay Gabany 4


1 Rensselaer Polytechnic Institute, Troy, New York, USA, and Earlham College, Richmond, Indiana, USA
2 The Observatories of the Carnegie Institution for Science, Pasadena, CA, USA
3 Astronomisches Rechen-Institut (ARI) am Zentrum fuer Astronomie der Universitaet Heidelberg (ZAH), Germany
4 Black Bird Observatory II, Alder Springs, California, USA


Abstract: In order to place the highly substructured stellar halos of the Milky Way and M31 in a larger context of hierarchical galaxy formation, it is necessary to understand the prevalence and properties of tidal substructure around external galaxies. This chapter details the current state of our observational knowledge of streams in galaxies in and beyond the Local Group, which are studied both in resolved stellar populations and in integrated light. Modeling of individual streams in extragalactic systems is hampered by our inability to obtain resolved stellar kinematics in the streams, though many streams contain alternate luminous kinematic tracers, such as globular clusters or planetary nebulae. We compare the observed structures to the predictions of models of galactic halo formation, which provide insight in the number and properties of streams expected around Milky Way like galaxies. More specifically, we discuss the inferences that can be made about stream progenitors based only on observed morphologies. We expand our discussion to consider hierarchical accretion at lower mass scales, in particular the observational evidence that substructure exists on smaller mass scales and the effects accretion events may have on the evolution of dwarf galaxies (satellite or isolated). Lastly, we discuss potential correlations between the presence of substructure in the halo and the structural properties of the disk. While many exciting discoveries have been made of tidal substructures around external galaxies, the “global” questions of galaxy formation and evolution via hierarchical accretion await a more complete census of the low surface brightness outskirts of galaxies in and beyond the Local Group.


Table of Contents

INTRODUCTION

STELLAR STREAMS: DETECTION METHODS AND EXAMPLES
Resolved stellar structures in the Local Group
Detection methods in and beyond the Local Group
Unresolved features beyond the Local Group
Resolved structures beyond the Local Group

N-BODY MODELING OF STREAMS

STELLAR TIDAL STREAMS AS A GALACTIC FORMATION DIAGNOSTIC

THE ROLE OF INTERACTIONS WITHIN DWARF GALAXY HALOS
Observational evidence for substructure at dwarf galaxy scales
Implications of dwarf-dwarf interactions

INDUCED STAR FORMATION, DISK STRUCTURE, AND TIDAL STREAMS

FUTURE PROSPECTS

REFERENCES

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