EDP Sciences
Free access
Issue A&A
Volume 432, Number 1, March II 2005
Page(s) 1 - 14
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20041488



A&A 432, 1-14 (2005)
DOI: 10.1051/0004-6361:20041488

Multi-density model of the ionised gas in NGC 253 using radio recombination lines

Niruj R. Mohan1, 2, 3, W. M. Goss4 and K. R. Anantharamaiah2

1  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: mgoss@aoc.nrao.edu

(Received 17 June 2004 / Accepted 26 October 2004)

Abstract
We have imaged the H92 $\alpha$ (8.3 GHz), H75 $\alpha$ (15 GHz), and H166 $\alpha$ (1.4 GHz) Radio Recombination Lines (RRLs) from NGC 253 at resolutions of 4.5 pc (0.4 $^{\prime\prime}$) , 2.5 pc (0.2 $^{\prime\prime}$) and 53 pc (4.5 $^{\prime\prime}$) respectively. The H92 $\alpha$ 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 ~10 4 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 ( >10 4 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

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Editor-in-Chief: T. Forveille
Letters Editor-in-Chief: J. Alves
Managing Editor: C. Bertout

ISSN: 0004-6361 ; e-ISSN: 1432-0746
Frequency: 12 volumes per year
Published by: EDP Sciences

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