Free-free and recombination radiation from massive star-forming regions
T. Beckert 1,2,
W.J. Duschl 1,3 and
P.G. Mezger 3
Received 26 August 1999 / Accepted 25 February 2000
The contribution of free-free and recombination radiation to the IR emission from regions of massive star formation is investigated. A method for calculating Gaunt factors for free-free emission from a hydrogenic non-relativistic gas is employed and the results are compared with approximation formula from the literature. While the cooling of ionized star forming regions due to free-free and free-bound transitions emerges in the MIR, which is dominated by dust emission, the overall cooling is mainly provided by line emission of heavier elements. Only in metal-free and therefore dust-free H II regions can free-free and free-bound radiation become dominant. We investigate the global energy balance of those regions and determine temperatures of the ionized gas, which are in general 2 to 8 times larger than found in present day star forming regions of massive stars.
Key words: radiation mechanisms: thermal ISM: H ii regions infrared: ISM: continuum radio continuum: general radio continuum: ISM
Send offprint requests to: W.J. Duschl, Institut für Theoretische Astrophysik, Tiergartenstrasse 15, 69121 Heidelberg, Germany (firstname.lastname@example.org)
Correspondence to: W.J. Duschl, Institut für Theoretische Astrophysik, Tiergartenstrasse 15, 69121 Heidelberg, Germany (email@example.com)
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© European Southern Observatory (ESO) 2000
Online publication: April 17, 2000