The Magellanic Stream

We lead an international collaboration focusing on the observational properties of the Magellanic Stream, a massive tail of gas stripped out of the Magellanic Clouds and falling into the Galactic halo. Our multi-wavelength research program uses Hubble, the VLT, radio telescopes and optical H-alpha measurements to determine the Stream's properties. We have made new contributions to understanding several key aspects of the Stream. First, we derived its metallicity and therefore origin; we used “chemical tagging” to show that gas from both Magellanic Clouds is present in the form of two interwoven filaments, one with an LMC abundance pattern and one with an SMC pattern. Second, we used customized photoionization models to derive its total mass accounting for ionized gas; we found that the Stream contains about three times as much ionized gas as neutral gas, which represented a substantial upward revision of the Stream’s mass. Third, we calculated its inflow rate onto the Galaxy, finding a higher value than the infall rate of all other HVCs combined. The Stream is now a poster child for how gas accretes from satellites onto centrals. Our work is continuing with a project (led by RIA Elaine Frazer) looking for kinematic differences between the low-ion and high-ion phases of the Stream, and for evidence of a Galactic Center flare that ionized the Stream several Myr ago.