From novak@clark.phys.nwu.edu Wed Jul 23 19:13:04 1997
Date: Wed, 23 Jul 97 12:29:21 CDT
From: novak@clark.phys.nwu.edu (Giles Novak)
To: hfalcke@mpifr-bonn.mpg.de
Subject:Possible abstract for you
Cc: cotera@ipac.caltech.edu
Content-Length: 1928
X-Status: 

\title{Polarized Far-infrared Emission from the Core and Envelope of the 
Sagittarius B2 Molecular Cloud}

\author{G. Novak, J.L. Dotson}

\institute{Department of Physics and Astronomy, Northwestern University }

\author{C.D. Dowell, R.H. Hildebrand, S.R. Platt, D. A. Schleuning}

\institute{Department of Astronomy and Astrophysics, and Enrico Fermi 
Institute, University of Chicago}

\author{P.F. Goldsmith}

\institute{National Astronomy and Ionosphere Center and Department of 
Astronomy, Cornell University}

\begin{abstract}

We have detected linear polarization in the 115 micron continuum 
radiation from the giant molecular cloud Sagittarius B2.  We found 
polarization at nine positions in the dense cloud core, and at fifteen 
positions in the less-dense envelope.  The polarization mechanism in 
the core is polarization due to absorption by magnetically aligned 
grains, and that in the envelope is polarized emission from 
magnetically aligned grains.  The inferred magnetic field direction is 
roughly North-South everywhere, but with spatially smooth 
variations of up to 30 degrees.  By considering our data together 
with Zeeman splitting observations we are able to set a conservative 
lower limit of 150 microGauss on the strength of the large-scale 
field in the envelope.  If large-scale fields this strong are common in 
Galactic Center clouds, they could be detectable via large-beam 
Zeeman measurements.  For positions in the envelope that are 
furthest from the core, the field is nearly parallel to the plane of the 
Galaxy.  This is consistent with the idea of a globally azimuthal 
magnetic field in the Galactic Center neutral gas layer, which is 
expected if gravitational forces dominate magnetic forces.
\end{abstract}