Journal Article

MAGMO: coherent magnetic fields in the star-forming regions of the Carina-Sagittarius spiral arm tangent

J. A. Green, N. M. McClure-Griffiths, J. L. Caswell, T. Robishaw and L. Harvey-Smith

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 425, issue 4, pages 2530-2547
Published in print October 2012 | ISSN: 0035-8711
Published online October 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.21722.x
MAGMO: coherent magnetic fields in the star-forming regions of the Carina-Sagittarius spiral arm tangent

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Abstract

We present the pilot results of the ‘;MAGMO’ project, targeted observations of ground-state hydroxyl masers towards sites of 6.7-GHz methanol maser emission in the Carina-Sagittarius spiral arm tangent, Galactic longitudes 280° to 295°. The ‘;MAGMO’ project aims to determine if Galactic magnetic fields can be traced with Zeeman splitting of masers associated with star formation. Pilot observations of 23 sites of methanol maser emission were made, with the detection of ground-state hydroxyl masers towards 11 of these and six additional offset sites. Of these 17 sites, nine are new detections of sites of 1665-MHz maser emission, three of them accompanied by 1667-MHz emission. More than 70 per cent of the maser features have significant circular polarization, whilst only ∼10 per cent have significant linear polarization (although some features with up to 100 per cent linear polarization are found). We find 11 Zeeman pairs across six sites of high-mass star formation with implied magnetic field strengths between –1.5 and +3.8 mG and a median field strength of +1.6 mG. Our measurements of Zeeman splitting imply that a coherent field orientation is experienced by the maser sites across a distance of 5.3 ± 2.0 kpc within the Carina-Sagittarius spiral arm tangent.

Keywords: magnetic fields; masers; polarization

Journal Article.  7212 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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