The Sagittarius dwarf galaxy: Where did all the gas go?
  The remarkable 1994 discovery of the Sagittarius dwarf galaxy (Sgr) revealed
that, together with the Magellanic Clouds (MCs), there are at least three major
dwarf galaxies, each with a total mass of order 10^10 - 10^11 solar masses,
falling onto the Galaxy in the present epoch. Beyond a Galactic radius of 300
kpc, dwarfs tend to retain their gas. At roughly 50 kpc, the MCs have
experienced substantial gas stripping as evidenced by the Magellanic Stream
which extends from them. Since Sgr experienced star formation long after it
fell into the Galaxy, it is interesting to explore just how and when this dwarf
lost its gas. To date, there has been no definitive detection of an associated
gas component. We revisit recent simulations of the stellar and dark matter
components of Sgr but, for the first time, include gas that is initially bound
to the infalling galaxy. We find that the gas stripping was 30 - 50 % complete
at its first disc crossing ~2.7 Gyr ago, then entirely stripped at its last
disc crossing ~1 Gyr ago. Our timeline is consistent with the last substantial
burst of star formation in Sgr which occurred about the time of the last disc
crossing. We discuss the consequences of gas stripping and conclude that the
vast majority of the stripped gas was fully settled onto the Galaxy by ~300 Myr
ago. It is highly unlikely that any of the high- or intermediate-velocity
clouds have a direct association with the Sgr dwarf.
