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Date and Time of the Query: 2018-12-16 T08:57:54 PST
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For refcode 2006AJ....132.2383T:
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Copyright by American Astronomical Society. Reproduced by permission
2006AJ....132.2383T Subarcsecond-Resolution Radio Maps of Nearby Spiral Galaxies Chao-Wei Tsai, Jean L. Turner, Sara C. Beck, Lucian P. Crosthwaite, Paul T. P. Ho, and David S. Meier Abstract. We report subarcsecond-resolution Very Large Array imaging of four nearby spiral galaxies: IC 342, Maffei II, NGC 2903, and NGC 6946. In each galaxy, compact radio continuum sources are identified in the central ~15"x15" region. These compact sources are responsible for 20% -- 30% of the total emission from the central kiloparsec of the host galaxies at 2 cm but only ~5% -- 10% at 6 cm. More than half of the compact sources appear to be H II regions. The H II regions with rising spectra must be fairly dense (n_i_~10^4^cm^-3^) and are presumably very young. The largest of these H II regions require the excitation of 500 -- 800 O stars within regions only a few parsecs in extent. These clusters approach the sizes expected for globular clusters. Thermal free-free emission from compact sources contributes more significantly at 2 cm, while diffuse synchrotron emission dominates at 6 cm. The radio H II regions are found near the centers of giant molecular clouds in projection and do not have obvious visual counterparts. Key words: Galaxies: Individual: IC 342, galaxies: individual (Maffei II), Galaxies: Individual: NGC 2903, Galaxies: Individual: NGC 6946, Galaxies: ISM, Galaxies: Spiral, Galaxies: Star Clusters, ISM: H II Regions, Radio Continuum: Galaxies
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