The Source of Maser Emission W33C (G12.8-0.2)

TL;DR

This study reports detailed observations of maser emissions in the W33C region, revealing variable H2O and OH masers, Zeeman splitting, and magnetic fields, suggesting complex cloud dynamics including rotation, outflows, and turbulence.

Contribution

First detailed measurement of maser emissions, Zeeman splitting, and magnetic fields in W33C, indicating complex molecular cloud dynamics.

Findings

Detected variable H2O maser features across broad velocity range

Discovered OH maser emission at 1667 MHz in specific velocity range

Measured Zeeman splitting indicating magnetic fields in the region

Abstract

Results of observations of the maser sources toward the W33C region (G12.8-0.2) carried out on the 22-m radio telescope of the Pushchino Radio Astronomy Observatory in the 1.35-cm H2O line and on the Large radio telescope in Nancay (France) in the main (1665 and 1667 MHz) and satellite (1612 and 1720 MHz) OH lines are reported. Multiple, strongly variable short-lived H2O emission features were detected in a broad interval of radial velocities, from -7 to 55 km/s. OH maser emission in the 1667-MHz line was discovered in a velocity range of 35-41 km/s. Stokes parameters of maser emission in the main OH lines 1665 and 1667 MHz were measured. Zeeman splitting was detected in the 1665-MHz line at 33.4 and 39.4 km/s and in the 1667 MHz line only at 39.4 km/s. The magnetic field intensity was estimated. A appreciable variability of Zeeman splitting components was observed at 39 and 39.8 km/s in both main lines. The extended spectrum and fast variability of the H2O maser emission together with the variability of the Zeeman splitting components in the main OH lines can be due to the composite clumpy structure of the molecular cloud and to the presence in it of large-scale rotation and bipolar outflow as well as of turbulent motions of material.