Statistical assessment of shapes and magnetic field orientations in molecular clouds through polarization observations
Abstract
We present a novel statistical analysis aimed at deriving the intrinsic shapes and magnetic field orientations of molecular clouds using dust emission and polarization observations by the Hertz polarimeter. Our observables are the aspect ratio of the projected plane-of-the-sky cloud image and the angle between the mean direction of the plane-of-the-sky component of the magnetic field and the short axis of the cloud image. To overcome projection effects due to the unknown orientation of the line-of-sight, we combine observations from 24 clouds, assuming that line-of-sight orientations are random and all are equally probable. Through a weighted least-squares analysis, we find that the best-fitting intrinsic cloud shape describing our sample is an oblate disc with only small degrees of triaxiality. The best-fitting intrinsic magnetic field orientation is close to the direction of the shortest cloud axis, with small (~24°) deviations towards the long/middle cloud axes. However, due to the small number of observed clouds, the power of our analysis to reject alternative configurations is limited.
Additional Information
© 2009 California Institute of Technology. US government sponsorship acknowledged. Journal compilation © 2009 RAS. Accepted 2009 July 8; received 2009 June 15; in original form 2009 April 3. KT thanks Shantanu Basu and Vasiliki Pavlidou for useful discussions, and Nick Scoville, Paul Goldsmith and Telemachos Mouschovias for feedback on the manuscript. We thank the referee, Carl Heiles, for insightful comments which helped us improve the manuscript. KT acknowledges support by NSF grants AST 02- 06216 and AST02-39759, by the NASA Theoretical Astrophysics Program grant NNG04G178G and by the Kavli Institute for Cosmological Physics at the University of Chicago through grants NSF PHY-0114422 and NSF PHY-0551142 and an endowment from the Kavli Foundation and its founder Fred Kavli. JEV acknowledges support from NSF AST 05-40882 through the Caltech Submillimeter Observatory. RH and LK acknowledge support from NSF grant AST 0505124. Part of this work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. © 2008. All rights reserved.Attached Files
Published - Tassis2009p6401Mon_Not_R_Astron_Soc.pdf
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Additional details
- Eprint ID
- 16784
- Resolver ID
- CaltechAUTHORS:20091123-113306370
- AST 02-06216
- NSF
- AST02-39759
- NSF
- NNG04G178G
- NASA
- NSF PHY-0114422
- Kavli Institute for Cosmological Physics
- NSF PHY-0551142
- Kavli Institute for Cosmological Physics
- Kavli Foundation, Fred Kavli
- AST 05-40882
- NSF
- AST 0505124
- NSF
- Created
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2009-11-24Created from EPrint's datestamp field
- Updated
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2021-11-08Created from EPrint's last_modified field