Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009aas...21336006h&link_type=abstract
American Astronomical Society, AAS Meeting #213, #360.06; Bulletin of the American Astronomical Society, Vol. 41, p.510
Astronomy and Astrophysics
Astronomy
Scientific paper
Star formation in galaxies is driven by the presence of molecular gas, but detecting that gas is difficult if the density and temperature are too low. We have developed a method of combining high-resolution HI and Far-UV data, along with gas metallicity data, to identify large-scale photodissociation regions (PDRs) located near areas of active star formation. We use these data to derive total hydrogen densities in the associated giant molecular clouds (GMCs).
Central to this method is the use of atomic hydrogen produced in the PDRs, combined with careful calculations of the UV radiation field. The atomic hydrogen is seen surrounding bright FUV sources, as is expected in PDRs. The size of these large scale PDRs is typically of the order of 100 parsec.
Combining results from M81, M83 and M33 we can give a comprehensive overview of candidate PDRs in these nearby spiral galaxies and their properties. In M33 especially, we analyzed the connection to CO emission and to PAH emission in order to test the PDR model in more detail, at scales as small as 30 pc. We find that the densities of the PDRs are similar across the three galaxies, despite apparent local differences in gas content. There is a statistical correspondence between GMCs with high molecular density and the presence of detectable CO emission.
Allen Rosalind J.
Heiner Jonathan S.
van der Kruit Pieter Corijnus
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