Unveiling the Hot Molecular Core in the Ultracompact \hii Region with Extended Emission G12.21--0.10

TL;DR

This study uses multiwavelength observations to identify and characterize a hot molecular core within the ultracompact HII region G12.21--0.10, revealing detailed physical properties and spatial associations.

Contribution

It provides the first detailed multiwavelength analysis of G12.21--0.10, identifying a hot molecular core and its physical parameters, advancing understanding of star formation regions.

Findings

Identification of two 3mm continuum peaks, one with the UC HII region and one with a molecular clump.

Detection of radio continuum and H41α line only toward the UC HII region.

Physical properties of the molecular clump suggest it is a hot molecular core.

Abstract

We present a multiwavelength study of the cometary \hii region G12.21--0.10 using the VLA and OVRO. Both radio continuum (0.3, 0.7, 2 and 3.6~cm) and spectral lines of H41$\alpha$, $^{13}$CS(2$-$1) \& (1$-$0), and NH$_{\rm 3}$(2,2) \& (4,4) observations are included. We find two 3~mm continuum peaks toward G12.21--0.10, one of them is spatially coincident with the UC~H~II region, while the other coincides spatially with a molecular clump. We also find that the 0.7, 2 and 3.6~cm continuum and H41$\alpha$ line are only detected toward the UC~H~II region, while the $^{13}$CS, and NH$_{\rm 3}$ is spatially associated with the molecular clump. Based on the morphology, kinetic temperature ($\sim$86~K), volumetric density ($\sim$1.5$\times$10$^6$~cm$^{-3}$) and linear size ($\sim$0.22~pc) of the molecular clump, we suggest this source is consistent with a hot molecular core.