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|Title:||Detection of an H92 alpha recombination line in the starburst galaxy NGC 660|
H ALPHA LINE,
VERY LARGE ARRAY (VLA),
H II REGIONS,
|Publisher:||Blackwell Publishing for the Royal Astronomical Society|
|Citation:||Monthly Notices of the Royal Astronomical Society, 1998, Vol.295, p156-166|
|Abstract:||We have used the Very Large Array (VLA) to search for the H92 alpha radio recombination line (RRL) in four starburst galaxies. In NGC 660, the line was detected over a 17 x 8 sq arcsec 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 2-8 x 10 exp 4 solar masses and the rate of production of UV photons NLyc = 1-3 x 10 exp 53/s. The ratio of H92 alpha and Br gamma line intensities in NGC 660 indicates that extinction is significant even at gamma = 2 microns. The velocity field of the ionized gas is consistent with a rotating disk with an average velocity gradient of 15 km/s arcsec. The dynamical mass within the central 500 pc is 4 x 10 exp 88 solar masses and may be about 6 x 10 exp 7 solar masses within the central 120 pc. No line was detected in the other galaxies (NGC 520, NGC 1614, and NGC 6946) to a 3 sigma limit of 300 microJy. In the starburst galaxies in which RRLs have been detected, we find that there is a rough correlation between the integrated H92 alpha line flux density and both the total far-infrared flux density and the radio continuum emission from the central region.|
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|Copyright:||(1998) Royal Astronomical Society|
|Appears in Collections:||Research Papers (A&A)|
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