Gas Kinematics in the HII regions G351.69-1.15 and G351.63-1.25

TL;DR

This study investigates the structure and kinematics of two neighboring H II regions using radio recombination lines, revealing dynamical broadening effects, turbulence, outflows, and velocity structures consistent with champagne flow and bipolar expansion models.

Contribution

First detailed radio recombination line analysis of these specific H II regions, linking ionized gas kinematics with molecular cloud dynamics and morphology.

Findings

Dynamical broadening significantly affects line profiles.

Ionized gas shows blue shift consistent with champagne flow.

Bipolar morphology linked to expanding ionized lobes within molecular cloud.

Abstract

We probe the structure and kinematics of two neighbouring H II regions identified as cometary and bipolar, using radio recombination lines (RRL). The H172{\alpha} RRLs from these H II regions: G351.6-1.15 and G351.6-1.25, are mapped using GMRT, India. We also detect carbon RRLs C172{\alpha} towards both these regions. The hydrogen RRLs display the effects of pressure and dynamical broadening in the line profiles, with the dynamical broadening (15 km/s) playing a major role in the observed profile of G351.6-1.15. We investigate the kinematics of molecular gas species towards this H II region from the MALT90 pilot survey. The molecular gas is mostly distributed towards the north and north-west of the cometary head. The molecular line profiles indicate signatures of turbulence and outflow in this region. The ionized gas at the cometary tail is blue shifted by 8 km/s with respect to the ambient molecular cloud, consistent with the earlier proposed champagne flow scenario. The relative velocity of 5 km/s between the northern and southern lobes of the bipolar H II region G351.6-1.25 is consistent with the premise that the bipolar morphology is a result of the expanding ionized lobes within a flat molecular cloud.