Study of the molecular and ionized gas in a possible precursor of an ultra-compact H II region M. E. Ortega, S. Paron, E. Giacani, M. Celis Peña, M. Rubio and A. Petriella A&A, 606 (2017) A61 Published online: 10 October 2017 DOI: 10.1051/0004-6361/201730879