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Free–Floating HI Clouds in the M 81 Group

Published online by Cambridge University Press:  01 June 2007

Elias Brinks ,
Fabian Walter  and
Evan D. Skillman
Elias Brinks
Affiliation:
Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB, United Kingdom email: [email protected]
Fabian Walter
Affiliation:
Max–Planck–Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany email: [email protected]
Evan D. Skillman
Affiliation:
Dept. of Astronomy, Univ. of Minnesota, 116 Church St. SE, Minneapolis, MN 55455, USA email: [email protected]
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Abstract

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Recent VLA observations pointed at dwarf spheroidal (dSph) galaxies in the M 81 group reveal a hitherto hidden population of extremely low mass (~ 105 M⊙) HI clouds with no obvious optical counterparts. We have searched 10 fields in the M 81 group totalling 2.2 square degree, both targeting known dwarf spheroidal galaxies and blank fields around the central triplet. Our observations show that the new population of low–mass HI clouds appears to be confined to a region toward the south–east of the central triplet (at distances of ~ 100 kpc from M 81). Possible explanations for these free–floating HI clouds are that they are related to the dSphs found to the South–East of M 81, that they belong to the galaxies of the M 81 triplet (equivalent to HVCs), that they are of primordial nature and provide fresh, unenriched material falling into the M 81 group, or that they are tidal debris from the 3–body interaction involving M 81–M 82–NGC 3077. Based on circumstantial evidence, we currently favour the latter explanation.

Keywords

galaxies: individual (M81)galaxies: interactionsintergalactic mediumradio lines: galaxies
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 3 , Symposium S244: Dark Galaxies and Lost Baryons , June 2007 , pp. 120 - 126
Copyright
Copyright © International Astronomical Union 2008

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