Enhanced density and magnetic fields in interstellar OH masers

Free access article

Issue		A&A Volume 458, Number 2, November I 2006


Page(s)		485 - 495
Section		Interstellar and circumstellar matter
DOI		http://dx.doi.org/10.1051/0004-6361:20065379

A&A 458, 485-495 (2006)
DOI: 10.1051/0004-6361:20065379

Enhanced density and magnetic fields in interstellar OH masers

V. L. Fish¹, M. J. Reid², K. M. Menten³ and T. Pillai³

¹ Jansky Fellow, National Radio Astronomy Observatory, PO Box O, 1003 Lopezville Road, Socorro, NM 87801, USA
e-mail: vfish@nrao.edu
² Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
³ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, Bonn 53121, Germany

(Received 6 April 2006 / Accepted 26 July 2006)

Abstract
Aims.We have observed the 6030 and 6035 MHz transitions of OH in high-mass star-forming regions to obtain magnetic field estimates in both maser emission and absorption.
Methods.Observations were taken with the Effelsberg 100 m telescope.
Results.Our observations are consistent with previous results, although we do detect a new 6030 MHz maser feature near -70 km s^-1 in the vicinity of W3(OH). In absorption we obtain a possible estimate of $-1.1 \pm 0.3$ mG for the average line-of-sight component of the magnetic field in the absorbing OH gas in K3-50 and submilligauss upper limits for the line-of-sight field strength in DR 21 and W3.
Conclusions.These results indicate that the magnetic field strength in the vicinity of OH masers is higher than that of the surrounding, non-masing material, which in turn suggests that the density of masing OH regions is higher than that of their surroundings.

Key words: masers -- stars: formation -- ISM: magnetic fields -- radio lines: ISM -- $\ion{H}{ii}$ regions -- ISM: molecules

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