The magnetic field structure in W51A^*

¹ Dept of Physical Sciences, University of Hertfordshire, Hatfield, HERTS, AL10 9AB, UK e-mail: a.chrysostomou,d.aitken,j.hough,r.curran@star.herts.ac.uk
² Joint Astronomy Centre, 660 N. A'ohoku Place, Hilo, HI 96720, USA e-mail: t.jenness,c.davis@jach.hawaii.edu
³ National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588, Japan e-mail: tamuramt@cc.nao.ac.jp

Corresponding author: A. Chrysostomou, a.chrysostomou@star.herts.ac.uk

Received: 12 September 2001
Accepted: 24 January 2002

Abstract

We present 850 μm imaging polarimetry of the W51A massive star forming region performed with SCUBA on the JCMT. From the polarimetry we infer the column-averaged magnetic field direction, projected onto the plane of the sky. We find that the magnetic field geometry in the region is complicated. We compare the field geometry with 6 cm and CS  emission and determine that the magnetic field must be relatively weak and plays a passive role, allowing itself to be shaped by pressure forces and dynamics in the ionised and neutral gases. Comparisons are drawn between our data and 1.3 mm BIMA interferometric polarimetry data, from which we conclude that the magnetic field must increase in importance as we move to smaller scales and closer to sites of active star formation.