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

Abstract

In the work presented here, the impact of magnetic field on the dynamical evolution of cometary globules Sim 129 and Sim 130 in the Sh2-236 HII 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 suggests that photoevaporated gas from the surfaces of Sim 129 and Sim 130 accumulates in clouds and starts streaming along the magnetic field lines. The 12CO (J=1–0) molecular line observations are performed towards NGC 1893 from the 14-m single dish radio telescope in Taeduk Radio Astronomy Observatory (TRAO). The velocity dispersion in the 12CO (J=1–0) molecular line and the dispersion in polarization angles are considered in the Davis-Chandrasekhar-Fermi formulation to estimate the magnetic field strength towards two Sim nebulae. The average value of field strength is found to be ∼60 μG with uncertainty of 0.5 times the estimated value.