A population of hypercompact H II regions identified from young H II regions A. Y. Yang, J. S. Urquhart, M. A. Thompson, K. M. Menten, F. Wyrowski, A. Brunthaler, W. W. Tian, M. Rugel, X. L. Yang, S. Yao and M. Mutale A&A, 645 (2021) A110 Published online: 22 January 2021 DOI: 10.1051/0004-6361/202038608