The Smith Cloud: Past, Present, and Future
Abstract
The Smith Cloud is a prominent high-velocity HI cloud with a well constrained distance that allows us to derive many of its physical properties. It contains several million solar masses of neutral and ionized gas, and is on a collision course with the Milky Way disk (Lockman et al. 2008, ApJ, 679, L2; Hill et al. 2009, ApJ 703, 1832; Hill et al. 2013, ApJ, 777, 55; Fox et al. 2016, ApJ, 816, L11). We have analyzed new 21cm HI data from the Green Bank Telescope (GBT) that cover hundreds of square-degrees around the Smith Cloud. They reveal previously unknown components of the Cloud that stretch out over a wide area. Compact HI features almost certainly associated with the Smith Cloud are found both trailing behind the Cloud's apparent direction of motion, and leading it. In all, the Cloud appears to extend more than 40 degrees across the sky, spanning Galactic latitudes from -40 degrees all the way through the Galactic plane to positive latitudes, with a continuity of velocity. We will discuss the results of fitting trajectories to the Cloud components that establish limits on its total velocity and trajectory through the Milky Way halo: it's past, present and its future. The Green Bank Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc. N. Pichette was funded by the NSF through the REU program at the Green Bank Observatory.
- Publication:
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American Astronomical Society Meeting Abstracts #233
- Pub Date:
- January 2019
- Bibcode:
- 2019AAS...23325608P