The Local Group: Inventory and History

Abstract

My presentation was an overview of what we know about the Local Group of galaxies, primarily from optical imaging and spectroscopy. AGB stars are on the whole a very sparse and unrepresentative stellar population in most Local Group galaxies. However, more detailed studies of star formation histories and chemical evolution properties of populations, like Main Sequence dwarf stars and Red Giant Branch stars, allow a better understanding of the evolutionary context in which AGB stars can be observed. There are a variety of galaxy types in the Local Group which range from predominantly metal poor (e.g., Leo A) to metal-rich (e.g., M 32). Dwarf galaxies are the most numerous type of galaxy in the Local Group, and provide the opportunity to study a relatively simple, typically metal-poor, environment that is likely similar to the conditions in the early history of all galaxies. Hopefully the range of star formation histories, peak star formation rates and metallicities will provide enough information to properly calibrate observations of AGB stars in more distant systems, and indeed in integrated spectra. Here I will summarise what we know about the star formation histories of nearby galaxies and their chemical evolution histories and then attempt to make a connection to their AGB star properties.Comment: Invited Review, "Why Galaxies Care About AGB Stars II", eds. Franz Kerschbaum, Thomas Lebzelter, and Bob Wing, Vienna, August 2010, 10 pages, 6 figure