OH maser towards IRAS 06056+2131: polarization parameters and evolution status

Abstract

We present high angular resolution observations of OH maser emission towards the high-mass star forming region IRAS 06056+2131. The observations were carried out using the UK radio interferometer array, Multi-Element Radio Linked Interferometer Network (MERLIN) in the OH main lines at 1665- and 1667-MHz, in addition to the OH satellite line at 1720-MHz. The results of this study reveal the small upper limit to the size of emission in the 1665-MHz line with an estimated total intensity of ∼4 Jy. We did not detect any emission from the 1667-MHz and 1720-MHz lines. The full polarization mode of MERLIN enables us to investigate the magnetic field in the OH maser region. In this transition, a Zeeman pair is identified from which a magnetic strength of ∼−1.5 mG is inferred. Our results show that IRAS 06056+2131 is highly polarized, with ∼ 96 % circular polarization and ∼ 6 % linear polarization. The linear polarization angle is ∼29○, implying a magnetic field which could be aligned with the outflow direction detected toward this region, but the actual magnetic field direction has an uncertainty of up to 110○ due to the possible effects of Faraday rotation. The star forming evolutionary status of the embedded proto-stellar object is discussed.

Stellar Evolution Studies Using Masers

“…The most commonly-found masers in star-formation are CH 3 OH, OH and H 2 O. Rarer masers in this context include SiO, H 2 CO and NH 3 . In addition to the work described below, recent papers from the EVN [10,11], VLBA [12], VERA & ALMA [13], MERLIN [14,15] and modelling [16] are noted. Maser polarization in star-forming regions is reviewed by [17].…”