In de la Fuente (2007; Ph. D. Thesis), the molecular clump associated with the ultracompact HII region G12.21–0.10 was confirmed as a large, hot, dense Hot Molecular Core nearby to the ionized gas. The density was confirmed by comparing low resolution NH3 (2,2) and (4,4) VLA observations, with other molecular lines and radio–continuum observations. These results will be presented in detail in a forthcoming paper (de la Fuente et al. in preparation). In these works, for the first time, the spatial location of the Hot Molecular Core is presented. Here we present the NH3 (4,4) observations from de la Fuente (2007; Ph. D. Thesis), confirming that the hotter and denser gas in the molecular core lies in a compact structure, of smaller scale than the NH3 (2,2) emission.
