2006/09/08 by Chao-Wei Tsai, Chao‐Wei Tsai, Tsai, Chao-Wei +13
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics (astro-ph) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0609210
4 pages including 2 figures. Proceedings of East Asian Young Astronomers Meeting, Kiyosato, Japan, February 2006
arxiv created 2006/09/08 · openalex publication_date 2006/09/08 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
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 (ni ~ 104 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.