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The Resolved Properties of Extragalactic Giant Molecular Clouds

Published online by Cambridge University Press:  01 June 2008

Alberto D. Bolatto ,
Adam K. Leroy ,
Erik Rosolowsky ,
Fabian Walter  and
Leo Blitz
Alberto D. Bolatto
Affiliation:
Department of Astronomy, University of Maryland, College Park, MD 20742, USA email: bolatto@astro.umd.edu
Adam K. Leroy
Affiliation:
Max-Planck-Institut für Astronomie, D-69117 Heidelberg, Germany
Erik Rosolowsky
Affiliation:
Department of Mathematics, Statistics, and Physics, University of British Columbia at Okanagan, Kelowna, B.C. V1V 1V7, Canada
Fabian Walter
Affiliation:
Max-Planck-Institut für Astronomie, D-69117 Heidelberg, Germany
Leo Blitz
Affiliation:
Department of Astronomy, University of California, Berkeley, CA94720, USA
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Abstract

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Giant molecular clouds (GMCs) are the major reservoirs of molecular gas in galaxies, and the starting point for star formation. As such, their properties play a key role in setting the initial conditions for the formation of stars. We present a comprehensive combined inteferometric/single-dish study of the resolved GMC properties in a number of extragalactic systems, including both normal and dwarf galaxies. We find that the extragalactic GMC properties measured across a wide range of environments, characterized by the Larson relations, are to first order remarkably compatible with those in the Milky Way. Using these data to investigate trends due to galaxy metallicity, we find that: 1) these measurements are not in accord with simple expectations from photoionization-regulated star formation theory; 2) there is no trend in the virial CO-to-H2 conversion factor on the spatial scales studied; and 3) there are measurable departures from the Galactic Larson relations in the Small Magellanic Cloud — the object with the lowest metallicity in the sample — where GMCs have velocity dispersions that are too small for their sizes. We will discuss the stability of these clouds in the light of our recent far-infrared analysis of this galaxy, and will contrast the results of the virial and far-infrared studies on the issue of the CO-to-H2 conversion factor and what they tell us about the structure of molecular clouds in primitive galaxies.

Keywords

ISM: cloudsgalaxies: ISMgalaxies: dwarf
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 4 , Issue S255: Low-Metallicity Star Formation: From the First Stars to Dwarf Galaxies , June 2008 , pp. 274 - 277
Copyright
Copyright © International Astronomical Union 2008

References

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