PROBING THE STRUCTURE AND KINEMATICS OF THE TRANSITION LAYER BETWEEN THE MAGELLANIC STREAM AND THE HALO IN H I
- Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706 (United States)
- School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS (United Kingdom)
- Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325 (United States)
The Magellanic Stream (MS) is a nearby laboratory for studying the fate of cool gas streams injected into a gaseous galactic halo. We investigate properties of the boundary layer between the cool MS gas and the hot Milky Way halo with 21 cm H I observations of a relatively isolated cloud having circular projection in the northern MS. Through averaging and modeling techniques, our observations, obtained with the Robert C. Byrd Green Bank Telescope, reach unprecedented 3{sigma} sensitivity of {approx}1 Multiplication-Sign 10{sup 17} cm{sup -2}, while retaining the telescope's 9.'1 resolution in the essential radial dimension. We find an envelope of diffuse neutral gas with FWHM of 60 km s{sup -1}, associated in velocity with the cloud core having FWHM of 20 km s{sup -1}, extending to 3.5 times the core radius with a neutral mass seven times that of the core. We show that the envelope is too extended to represent a conduction-dominated layer between the core and the halo. Its observed properties are better explained by a turbulent mixing layer driven by hydrodynamic instabilities. The fortuitous alignment of the NGC 7469 background source near the cloud center allows us to combine UV absorption and H I emission data to determine a core temperature of 8350 {+-} 350 K. We show that the H I column density and size of the core can be reproduced when a slightly larger cloud is exposed to Galactic and extragalactic background ionizing radiation. Cooling in the large diffuse turbulent mixing layer envelope extends the cloud lifetime by at least a factor of two relative to a simple hydrodynamic ablation case, suggesting that the cloud is likely to reach the Milky Way disk.
- OSTI ID:
- 22086325
- Journal Information:
- Astrophysical Journal, Vol. 760, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
Similar Records
THE COS/UVES ABSORPTION SURVEY OF THE MAGELLANIC STREAM. I. ONE-TENTH SOLAR ABUNDANCES ALONG THE BODY OF THE STREAM
A SEARCH FOR DIFFUSE NEUTRAL HYDROGEN AND H I CLOUDS IN THE NGC 2403 GROUP