X-raying Galaxies: A Chandra Legacy
  This presentation reviews Chandra's major contribution to the understanding
of nearby galaxies. After a brief summary on significant 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 first 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 outflows. 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.
