Detection of an H92α recombination line in the starburst galaxy NGC 660

Phookun, B. ; Anantharamaiah, K. R. ; Goss, W. M. (1998) Detection of an H92α recombination line in the starburst galaxy NGC 660 Monthly Notices of the Royal Astronomical Society, 295 (1). pp. 156-166. ISSN 0035-8711

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We have used the Very Large Array (VLA) to search for the H92α radio recombination line (RRL) in four starburst galaxies. In NGC 660, the line was detected over a 17Å-8 arcsec2 region near its starburst nucleus. The line and continuum emission indicate that the RRL-emitting gas is most likely in the form of a cluster of H ii regions with a small filling factor. Using a simple model we find that the total ionized mass in the nuclear region is in the range 2-8Å-104 M⊙ and the rate of production of UV photons NLyc~1-3Å-1053 s-1. The ratio of H92α and Brγ line intensities in NGC 660 indicates that extinction is significant even at λ=2 µm. The velocity field of the ionized gas is consistent with a rotating disc with an average velocity gradient of ~15 km s-1 arcsec-1. The dynamical mass within the central 500 pc is ~4Å-108 M and may be about ~6Å-107 M within the central 120 pc. No line was detected in the other galaxies (NGC 520, NGC 1614 and NGC 6946) to a 3s limit of 300 µJy. In the starburst galaxies in which RRLs have been detected, we find that there is a rough correlation between the integrated H92α line flux density and both the total far-infrared flux density and the radio continuum emission from the central region.

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Deposited On:15 Dec 2010 12:39
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