Publication Date

2010

Comments

This is the pre-published version harvested from ArXiv.

Abstract

This presentation reviews Chandra's major contribution to the understanding of nearby galaxies.
After a brief summary on signi cant advances in characterizing various types of discrete X-ray
sources, the presentation focuses on the global hot gas in and around galaxies, especially normal
ones like our own. The hot gas is a product of stellar and AGN feedback | the least understood
part in theories of galaxy formation and evolution. Chandra observations have led to the rst
characterization of the spatial, thermal, chemical, and kinetic properties of the gas in our Galaxy.
The gas is concentrated around the Galactic bulge and disk on scales of a few kpc. The column
density of chemically-enriched hot gas on larger scales is at least an order magnitude smaller,
indicating that it may not account for the bulk of the missing baryon matter predicted for the
Galactic halo according to the standard cosmology. Similar results have also been obtained for
other nearby galaxies. The X-ray emission from hot gas is well correlated with the star formation
rate and stellar mass, indicating that the heating is primarily due to the stellar feedback.
However, the observed X-ray luminosity of the gas is typically less than a few percent of the
feedback energy. Thus the bulk of the feedback (including injected heavy elements) is likely lost
in galaxy-wide out
ows. The results are compared with simulations of the feedback to infer its
dynamics and interplay with the circum-galactic medium, hence the evolution of galaxies.