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C.A. Rodriguez-Rico (NRAO-UNAM), W.M. Goss (NRAO), J.H. Zhao (CfA)
We present high-resolution (~1\arcsec) observations of radio recombination lines (RRL) H92\alpha (3.6 cm) and H53\alpha (0.7 mm) from the starburst galaxies M82, NGC 253 and Arp 220 using the VLA of the NRAO. By using the H92\alpha RRL observations we obtained the velocity field in the central regions of M82 and NGC 253. For M82 we fitted a rotation curve for the ionized gas. The inclination of the plane of rotation was found to be ~70o, a position angle of 65o, center of rotation at 200 km s-1 and observed solid body rotation for the central ~150 pc. In the superbubble region of M82, the peaks in the integrated emission of H92\alpha line emission are coincident with the 12CO line emission, implying close interaction of the ionized and molecular gas and resembling the shell structure proposed by Wills et al. (1999).
We modeled the H92\alpha and H53\alpha RRLs emission by using low-density and high-density HII regions and derived values for densities (103, 105 cm-3) temperatures (~5\times 103 K), sizes (5, 0.05 pc) and number of HII regions (~500, 50) that fit the observations. The H53\alpha line emission is detected from a few compact sources. From the models we found that the H53\alpha line emission arises in a few high density HII regions.
The National Radio Astronomy Observatory (NRAO) is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.