The Astrophysical Journal, 702:940–954, 2009 September 10
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doi:10.1088/0004-637X/702/2/940
2009. The American Astronomical Society. All rights reserved. Printed in the U.S.A.
PROPERTIES AND ORIGIN OF THE HIGH-VELOCITY GAS TOWARD THE LARGE MAGELLANIC CLOUD
1 Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556, USA 2 School of Physics M013, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia
N. Lehner1 , L. Staveley-Smith2 , and J. C. Howk1
Received 2009 May 22; accepted 2009 July 16; published 2009 August 17
ABSTRACT In the spectra of 139 early-type Large Magellanic Cloud (LMC) stars observed with Far Ultraviolet Spectroscopic Explorer and with deep radio Parkes H i 21 cm observations along with those stars, we search for and analyze the absorption and emission from high-velocity gas at +90 vLSR +175 km s1 . The H i column density of the highvelocity clouds (HVCs) along these sightlines ranges from 106 M ) HVC complex that is linked to stellar feedback occurring in a dwarf spiral galaxy. Key words: galaxies: halos – galaxies: interactions – galaxies: kinematics and dynamics – galaxies: structure – Magellanic Clouds Online-only material: color gures
1. INTRODUCTION The interactions of galaxies and the nearby intergalactic medium (IGM) through the accretion of matter onto galaxies or the expulsion of matter and energy in winds from galaxies are crucial for the evolution of both the galaxies and the IGM. The star formation histories, gas content, and metallicity of a galaxy are co-dependent on both internal processes and on the interaction between the galaxy and the local IGM. Today's star-forming galaxies are continuing to form by accreting gas from the nearby IGM, from matter condensing out of a hot corona (e.g., Peek et al. 2008), from the stripped ISM of smaller dwarf systems (e.g., Putman et al. 1998), or even from matter ejected by earlier star formation episodes (Bertone et al. 2007; Bouch et al. 2007); much of the accretion may proceed through e analogs to the high-velocity clouds (HVCs) found about the Milky Way (MW, e.g., Wakker et al. 2007; Lockman et al. 2008; Thom et al. 2008). The continued formation of stars in galaxies without depleting the available gas and the observed metallicity distribution of long-lived stars in our galaxies require a continuous infall of low-metallicity matter (e.g., van den Bergh 1962; Tinsley 1981; Matteucci 2003; Bland-Hawthorn 2008). Balancing the accretion of new matter, feedback from strong star formation can drive large-scale circulations of gas away from the disk or outows that feed matter into the nearby IGM (e.g., Veilleux et al. 2005; Simcoe et al. 2006; Oppenheimer &

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