An analysis of the distribution of background star polarization in dark clouds
Abstract
The polarization observed for stars background to dark clouds (Bok Globules) is often used as diagnostic to study the ongoing star formation processes in these clouds. Such polarization in the optical have been reported for eight nearby clouds CB3, CB25, CB39, CB52, CB54, CB58, CB62 and CB246 in one of our previous work (Sen et. al. 2000). With a view to understand the origin of this polarization, the the present work attempts are made to look for any possible relation between this observed polarization and other physical parameters in the cloud (like temperature, turbulence etc.). The observed polarization does not seem to be clearly related to the dust and gas temperatures (Td and Tg) in the cloud as expected from the Davis-Greenstein grain alignment mechanism (Davis & Greenstein, 1952). However, the average observed polarization pav appears to be related to the turbulence delta V (measured by 12CO line width) by the mathematical relation pav=2.95exp(-0.24delta V). The possible realtion between the direction of polarization vector and other physical parameters are also discussed. For this analysis, in addition to the data on above eight clouds, the data on CB4 (Kane et. al., 1995) are also included for comparison.
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