Title:	Modelling carbon radio recombination line observations towards the ultracompact H II region W48A
Authors:	Jeyakumar, S. Roshi, Anish D.
Keywords:	atomic processes ISM: clouds radio lines: ISM
Issue Date:	1-Oct-2013
Publisher:	Oxford University Press
Citation:	Monthly Notices of the Royal Astronomical Society, 2013, Vol. 434, p2742.
Abstract:	We model the carbon recombination line (CRL) emission from the photodissociation region (PDR) surrounding the ultracompact (UC) H ii region W48A. Our modelling shows that the inner regions (AV ∼ 1) of the C ii layer in the PDR contribute significantly to the CRL emission. Using models spanning over a large range of parameters that are typical for the environments of UCH ii regions, we explore the dependence of the line ratios of CRL emission on the density of the PDR and on the far-ultraviolet radiation incident in the region. We find that it is possible to constrain the density of the PDR by observing a suitable set of CRLs. If the neutral density in the PDR is high ( ≳ 107 cm−3), then the CRL emission is bright at high frequencies ( ≳ 20 GHz), and the absorption lines from such regions can be detected at low frequencies ( ≲ 10 GHz). By modelling CRL observations towards W48A, we can show that the UCH ii region is embedded in a molecular cloud with a density of about 4 × 107 cm−3
Description:	Restricted Access. An open-access version is available at arXiv.org (one of the alternative locations)
URI:	http://hdl.handle.net/2289/5853
ISSN:	1745-3933 (online)
Alternative Location:	http://adsabs.harvard.edu/abs/2013MNRAS.434.2742J http://arxiv.org/abs/1306.3147 http://dx.doi.org/10.1093/mnras/stt1073
Copyright:	2013 The Authors &The Royal Astronomical Society
Appears in Collections:	Research Papers (A&A)

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