The Masers Towards IRAS 20126+4104

TL;DR

This study uses MERLIN observations to analyze OH, water, and methanol masers near IRAS 20126+4104, revealing disk rotation, magnetic fields, and maser variability in a high-mass star-forming region.

Contribution

First detailed MERLIN maser observations of IRAS 20126+4104, linking maser emissions to disk structure, magnetic fields, and outflow activity in a high-mass star formation context.

Findings

OH and methanol masers trace the circumstellar disk with Keplerian rotation.

Magnetic field strength around 11 mG detected via Zeeman splitting.

Water masers are offset and variable, associated with outflows.

Abstract

We present MERLIN observations of OH, water and methanol masers towards the young high mass stellar object IRAS 20126+4104. Emission from the 1665-MHz OH, 22-GHz H_2O and 6.7-GHz CH_3OH masers is detected and all originates very close to the central source. The OH and methanol masers appear to trace part of the circumstellar disk around the central source. The positions and velocities of the OH and methanol masers are consistent with Keplerian rotation around a central mass of ~ 5 Msun. The water masers are offset from the OH and methanol masers and have significantly changed since they were last observed, but still appear to be associated to the outflow from the source. All the OH masers components are circularly polarised, in some cases reaching 100 percent while some OH components also have linear polarisation. We identify one Zeeman pair of OH masers and the splitting of this pair indicates a magnetic field of strength ~ 11 mG within ~ 0.5" (850 AU) of the central source. The OH and methanol maser emission suggest that the disk material is dense, n > 10^6 cm^-3, and warm, T > 125 K and the high abundance of methanol required by the maser emission is consistent with the evaporation of the mantles on dust grains in the disk as a result of heating or shocking of the disk material