Volume 432, Number 1, March II 2005
|Page(s)||1 - 14|
|Published online||22 February 2005|
Multi-density model of the ionised gas in NGC 253 using radio recombination lines*
Institut d'Astrophysique de Paris, 98 bis boulevard Arago, 75014 Paris, France
2 Raman Research Institute, C.V. Raman Avenue, Sadashivanagar Post Office, Bangalore 560080, India
3 Joint Astronomy Program, Department of Physics, Indian Institute of Science, Bangalore 560012, India
4 National Radio Astronomy Observatory, PO Box O, Socorro, NM 87801, USA e-mail: email@example.com
Accepted: 26 October 2004
We have imaged the H92α (8.3 GHz), H75α (15 GHz), and H166α (1.4 GHz) Radio Recombination Lines (RRLs) from NGC 253 at resolutions of 4.5 pc (0.4″) , 2.5 pc (0.2″) and 53 pc (4.5″) respectively. The H92α line arises from individual compact sources, most of which possess radio continuum counterparts. The line widths range from ~200 km s-1 for the sources near the radio nucleus to 70–100 km s-1 for the extranuclear ones. These lines are emitted by gas at a density ~104 cm-3. The remainder of the cm-wave RRLs arise in lower density gas (~500 cm-3) with a higher area filling factor and with ten times higher mass. A third component of higher density gas (>104 cm-3) is required to explain the mm-wave RRLs.
Key words: galaxies: individual: NGC 253 / galaxies: ISM / galaxies: starburst / radio lines: galaxies / radio lines: ISM
© ESO, 2005
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