Annu. Rev. Astron. Astrophys. 1998. 36: 435-506
Copyright © 1998 by . All rights reserved

Reprinted with kind permission from , 4139 El Camino Way, Palo Alto, California, USA

DWARF GALAXIES OF THE LOCAL GROUP

Mario Mateo


Department of Astronomy, University of Michigan, Ann Arbor, Michigan 48109-1090;
e-mail: mateo@astro.lsa.umich.edu

Key Words: stellar populations, Local Group galaxies, photometry, galaxy formation, spectroscopy, dark matter, interstellar medium

Abstract. The Local Group dwarf galaxies offer a unique window to the detailed properties of the most common type of galaxy in the Universe. In this review, I update the census of Local Group dwarfs based on the most recent distance and radial velocity determinations. I then discuss the detailed properties of this sample, including (a) the integrated photometric parameters and optical structures of these galaxies, (b) the content, nature, and distribution of their interstellar medium (ISM), (c) their heavy-element abundances derived from both stars and nebulae, (d) the complex and varied star-formation histories of these dwarfs, (e) their internal kinematics, stressing the relevance of these galaxies to the "dark matter problem" and to alternative interpretations, and (f) evidence for past, ongoing, and future interactions of these dwarfs with other galaxies in the Local Group and beyond. To complement the discussion and to serve as a foundation for future work, I present an extensive set of basic observational data in tables that summarize much of what we know and do not know about these nearby dwarfs. Our understanding of these galaxies has grown impressively in the past decade, but fundamental puzzles remain that will keep the Local Group at the forefront of galaxy evolution studies for some time.

Table of Contents

INTRODUCTION

THE CENSUS OF LOCAL GROUP DWARFS
Membership in the Local Group
What's Missing?
The Structure of the Local Group

OPTICAL PHOTOMETRIC AND STRUCTURAL PROPERTIES OF LOCAL GROUP DWARFS
Integrated Photometry
Structural Properties

THE ISM OF LOCAL GROUP DWARFS
HI Content and Distribution
Dust and Molecular Gas
HII Regions, SN Remnants and X-Rays
The ISM `Crisis' in dSph Galaxies

CHEMICAL ABUNDANCES IN LOCAL GROUP DWARFS
The Observational Basis for LG Dwarf Abundances
The Metallicity-Luminosity Relation and the dIrr/dSph Connection

STAR FORMATION HISTORIES OF LOCAL GROUP DWARFS
Basic Techniques and Ingredients
Age Indicators in Local Group Dwarfs
A Compilation of Star-Formation Histories of Local Group Dwarfs

INTERNAL KINEMATICS OF LOCAL GROUP DWARFS
The Observational Basis for Dark Matter
Constraints on Dark Matter in Local Group Dwarfs
Alternatives to Dark Matter

INTERACTIONS IN THE LOCAL GROUP

CONCLUSIONS

REFERENCES

For a postscript version of the article, click here.

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