Journal
ASTRONOMY & ASTROPHYSICS
Volume 489, Issue 2, Pages 533-U28Publisher
EDP SCIENCES S A
DOI: 10.1051/0004-6361:200810430
Keywords
galaxies : individual : M83; galaxies : ISM; ISM : clouds; ISM : molecules; ultraviolet : galaxies; radio lines : galaxies
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Funding
- STScI Director's Discretionary Research Fund
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Using observed GALEX far-ultraviolet (FUV) fluxes and VLA images of the 21-cm HI column densities, along with estimates of the local dust abundances, we measure the volume densities of a sample of actively star-forming giant molecular clouds (GMCs) in the nearby spiral galaxy M83 on a typical resolution scale of 170 pc. Our approach is based on an equilibrium model for the cycle of molecular hydrogen formation on dust grains and photodissociation under the influence of the FUV radiation on the cloud surfaces of GMCs. We find a range of total volume densities on the surface of GMCs in M83, namely 0.1-400 cm(-3) inside R(25), 0.5-50 cm(-3) outside R(25). Our data include a number of GMCs in the HI ring surrounding this galaxy. Finally, we discuss the effects of observational selection, which may bias our results.
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