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Title: THE COS/UVES ABSORPTION SURVEY OF THE MAGELLANIC STREAM. II. EVIDENCE FOR A COMPLEX ENRICHMENT HISTORY OF THE STREAM FROM THE FAIRALL 9 SIGHTLINE

We present a multi-wavelength study of the Magellanic Stream (MS), a massive gaseous structure in the Local Group that is believed to represent material stripped from the Magellanic Clouds. We use ultraviolet, optical and radio data obtained with HST/COS, VLT/UVES, FUSE, GASS, and ATCA to study metal abundances and physical conditions in the Stream toward the quasar Fairall 9. Line absorption in the MS from a large number of metal ions and from molecular hydrogen is detected in up to seven absorption components, indicating the presence of multi-phase gas. From the analysis of unsaturated S II absorption, in combination with a detailed photoionization model, we obtain a surprisingly high {alpha} abundance in the Stream toward Fairall 9 of [S/H] = -0.30 {+-} 0.04 (0.50 solar). This value is five times higher than what is found along other MS sightlines based on similar COS/UVES data sets. In contrast, the measured nitrogen abundance is found to be substantially lower ([N/H] = -1.15 {+-} 0.06), implying a very low [N/{alpha}] ratio of -0.85 dex. The substantial differences in the chemical composition of MS toward Fairall 9 compared to other sightlines point toward a complex enrichment history of the Stream. We favor a scenario,more » in which the gas toward Fairall 9 was locally enriched with {alpha} elements by massive stars and then was separated from the Magellanic Clouds before the delayed nitrogen enrichment from intermediate-mass stars could set in. Our results support (but do not require) the idea that there is a metal-enriched filament in the Stream toward Fairall 9 that originates in the LMC.« less
Authors:
;  [1] ;  [2] ;  [3] ; ;  [4] ;  [5] ;  [6]
  1. Institut fuer Physik und Astronomie, Universitaet Potsdam, Haus 28, Karl-Liebknecht-Str. 24/25, D-14476 Golm (Potsdam) (Germany)
  2. Space Telescope Science Institute, Baltimore, MD 21218 (United States)
  3. Department of Astronomy, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI 53706 (United States)
  4. Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States)
  5. Institute of Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia)
  6. Argelander-Institut fuer Astronomie, Universitaet Bonn, Auf dem Huegel 71, D-53121 Bonn (Germany)
Publication Date:
OSTI Identifier:
22121799
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 772; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; ABUNDANCE; COMPLEXES; HYDROGEN; IONS; MAGELLANIC CLOUDS; METALS; NITROGEN; PHOTOIONIZATION; QUASARS; STARS; STREAMS; ULTRAVIOLET RADIATION; WAVELENGTHS