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Astron. Astrophys. Suppl. Ser. 141, 175-183

Imaging polarimetry of some selected dark clouds

A.K. Sen^1,4 - Ranjan Gupta² - A.N. Ramaprakash³ - S.N. Tandon²

Send offprint request: R. Gupta

1 - Department of Physics, Assam University, Silchar 788 014, India
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2 - IUCAA, Post Bag 4, Ganeshkhind, Pune 411007, India
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3 - Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK
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4 - also Senior Associate at IUCAA

Received November 2, 1998; accepted July 23, 1999

Abstract:

A set of eight Bok Globules CB3, CB25, CB39, CB52, CB54, CB58, CB62 and CB246 were observed polarimetrically in white light, using our Imaging Polarimeter (IMPOL), from the 1.2 m IR telescope at Mount Abu, India. The observations were carried out on different nights during the period December 1997 and April 1998. The CCD images obtained from the instrument (IMPOL) were analyzed, to produce polarization map of the Bok Globules. The stars in the field, which are mostly background to the cloud show typically 2% of linear polarization. Clouds which are less dynamic (having $^{12}\rm CO$ line widths $\Delta \rm V < 2.5$ km s^-1), in general show slightly better alignment of polarization vectors with the projected direction of galactic plane. On the other hand the more dynamic group of clouds, has the polarization vectors more scattered and poorly aligned with the projected direction of the galactic plane. However one of the clouds observed CB58 does not follow this trend very well.

Key words: dark clouds -- ISM: dust -- ISM: magnetic field-polarization-polarimeter -- techniques: polarimetric