On the photo-evaporation, dust polarization, and kinematics of two nebulae in Sh2-236

TL;DR

This study investigates the magnetic field influence on the evolution and gas dynamics of two nebulae in Sh2-236, combining optical polarization, radio continuum, and molecular line observations to analyze magnetic field strength and gas streaming.

Contribution

It provides new insights into the magnetic field morphology and strength in nebulae, linking polarization and molecular data to understand photoevaporation and gas kinematics.

Findings

Magnetic field strength is approximately 60 μG.

Photoevaporated gas streams along magnetic field lines.

Correlation between polarization and radio emission indicates magnetic influence.

Abstract

In the work presented here, the impact of magnetic field on the dynamical evolution of cometary globules Sim 129 and Sim 130 in Sh2-236 H\,II region and the ionized gas streaming out of their surfaces is investigated. The magnetic field morphology in the region associated with these globules is inferred using optical polarization measurements with the Sampurnanand Telescope at ARIES. The nebular emission is probed through radio continuum mapping at 1.4~GHz with the archival National Radio Astronomy Observatory (NRAO) very large array (VLA) Sky Survey (NVSS) data. The correlation of these measurements suggest that the photoevaporated gas from the surfaces of Sim 129 and Sim 130 is accumulated in clouds and starts streaming along the magnetic field lines. The $\rm ^{12}CO$ (J=1-0) molecular line observations are performed towards NGC\,1893 from 14-m single dish radio telescope in Taeduk Radio Astronomy Observatory (TRAO). The velocity dispersion in $\rm ^{12}CO$ (J=1-0) molecular line and the dispersion in polarization angles are used in Davis-Chandrasekhar-Fermi formulation to estimate the magnetic field strength towards two sim nebulae. The average value of field strength is found to be $\sim$60$\mu$G with uncertainty of 0.5 times the estimated value.