Title:	Detection of H92 alpha recombination line from the galaxies NGC 3628, IC 694, and NGC 1365
Authors:	Anantharamaiah, K.R. Zhao, J.H. Goss, W.M. Viallefond, F.
Keywords:	GALAXIES INDIVIDUAL NGC NUMBER NGC 1365 NGC 3628 GALAXIES: INDIVIDUAL ALPHANUMERIC: IC 694 GALAXIES: NUCLEI RADIO LINES: GALAXIES
Issue Date:	Dec-1993
Publisher:	The University of Chicago Press for the American Astronomical Society
Citation:	Astrophysical Journal, 1993, Vol.419, p585-595
Abstract:	Using the Very Large Array with an angular resolution of 3", we have detected the hydrogen recombination line H92alpha (Vrest = 8309.38 MHz) from the starburst nuclei in the galaxies NGC 3628 and IC 694 and also from the Seyfert II nucleus in NGC t365. In each case the line-emitting region extends over a few hundred parsecs. The detected lines have peak intensities in the range 0.5-1.5 mJy and widths (FWHM) 200- 400 km s 1 The line was not detected in three other galaxies (NGC 262, NGC 1068, and NGC 3079) that were observed to a similar sensitivity level. We present a model in which a collection of H ii regions in the nuclear region accounts for the observed H92alpha line. The required number of H ii regions, their temperature, electron density, and linear size are constrained by the observed line flux density, line width, continuum spectrum, and size of the line-emitting region. If the temperature of the H ii regions is above 5000 K, then electron densities in the range 5-50 x 103 cm -3 are permitted by the available constraints. Several hundred H ii regions of a few parsecs in size, with a total mass of a few times 10 M_{0}, are required to account for the observed line flux density. The rate of production of Lyman continuum photons required to maintain the ionization is a few times 10 s -1 Much of the line emission comes from internal stimulated emission due to the continuum generated within the H ii regions which account for 5%-30% of the observed total continuum at 5 GHz. Predictions are made for the expected recombination line and continuum flux density as a function of frequency from the nuclear region of the galaxies.
URI:	http://hdl.handle.net/2289/1435
ISSN:	0004-637X 1538-4357 (online)
Alternative Location:	http://adsabs.harvard.edu/cgi-bin/bib_query?1993ApJ...419..585A
Copyright:	(1993) by the American Astronomical Society. Scanned images provided by the NASA ADS Data System.
Appears in Collections:	Research Papers (A&A)

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