  The Milky Way and all other galaxies are missing most of their baryons in
that the ratio of the known baryonic mass to the gravitating mass (within the
virial radius), is several times less than the cosmic ratio determined from
WMAP. This implies that either the baryons never fell into galaxies or that
powerful galactic winds removed most of the baryons. It is possible to
discriminate between these two pathways if we can discover the missing baryons
and measure its properties: spatial distribution; temperature; and metallicity.
The missing baryons from galaxies are expected to have temperatures of 1-3E6 K,
so X-ray observations are required. In this white paper, we show how X-ray
observations, obtained with a facility such as IXO, can be used to identify and
study these elusive baryons.
