TY  - JOUR
A1  - Richter, Philipp
A1  - Fox, Andrew J.
A1  - Wakker, Bart P.
A1  - Lehner, Nicolas
A1  - Howk, J. Christopher
A1  - Bland-Hawthorn, Joss
A1  - Ben Bekhti, Nadya
A1  - Fechner, Cora
T1  - The COS/UVES absorption survey of the magellanic stream - II. Evidence  for a complex enrichment history of the stream from the fairall 9 sightline
T2  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - 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, in which the gas toward Fairall 9 was locally enriched with a 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.
KW  - Galaxy: evolution
KW  - Galaxy: halo
KW  - ISM: abundances
KW  - Magellanic Clouds
KW  - quasars: absorption lines
Y1  - 2013
UR  - https://publishup.uni-potsdam.de/frontdoor/index/index/docId/34840
SN  - 0004-637X
VL  - 772
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  -