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Paper: Mid-Infrared Ionic Line Observations of Ultracompact HII Regions: Ionization by Massive Star Clusters
Volume: 267, Hot Star Workshop III: the Earliest Stages of Massive Star Birth
Page: 399
Authors: Okamoto, Y. K.; Kataza, H.; Yamashita, T.; Miyata, T.; Sako, S.; Takubo, S.; Honda, M.; Onaka, T.
Abstract: The ionizing star masses of ultracompact (UC) HII regions, W51 IRS2 and K3-50A, are estimated by the observations from [NeII] 12.8 micron, [ArIII] 8.99 micron, and [SIV] 10.51 micron, which have different ionizing potentials. The line flux ratios suggest much later spectral types for the ionizing sources than the radio continuum does. The UC HII regions are likely to be ionized by massive star clusters.
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