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High Resolution Radio Maps of Four Nearby Spiral Galaxies

Chao-Wei Tsai·Jean L. Turner·Sara C. Beck·Lucian P. Crosthwaite·Paul T. P. Ho·David S. Meier·;
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Abstract

We report subarcsecond-resolution VLA imaging of the centers of four nearby spiral galaxies: IC 342, Maffei II, NGC 2903, and NGC 6946. In each galaxy, 7 - 12 compact radio continuum sources were identified within the central 15" x 15". Slightly over half of the compact sources appear to be HII regions with flat or positive spectral indices (alpha >~ -0.1). The HII regions with rising spectra are optically thick at centimeter wavelengths, and thus dense (n_i ~ 10^4 cm^(-3)) and young. The largest of these HII regions require the excitation of 500 - 800 O stars, within regions of only few parsecs extent. These clusters approach the sizes expected for globular clusters.

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Chao-Wei Tsai, Jean L. Turner, Sara C. Beck, Lucian P. Crosthwaite, Paul T. P. Ho, David S. Meier, ;. 2006-09-08. High Resolution Radio Maps of Four Nearby Spiral Galaxies. https://arxiv.org/abs/astro-ph/0609210

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