Study of grain alignment efficiency and a distance estimate for small globule CB4

Abstract

We study the polarization efficiency (defined as the ratio of polarization to extinction) of stars in the background of the small, nearly spherical and isolated Bok globule CB4 to understand the grain alignment process. A decrease in polarization efficiency with an increase in visual extinction is noticed. This suggests that the observed polarization in lines of sight which intercept a Bok globule tends to show dominance of dust grains in the outer layers of the globule. This finding is consistent with the results obtained for other clouds in the past. We determined the distance to the cloud CB4 using near-infrared photometry (2MASS JHKS colors) of moderately obscured stars located at the periphery of the cloud. From the extinction-distance plot, the distance to this cloud is estimated to be ($459\pm 85$) pc.

arXiv comment11 pages, 4 figures; Accepted in Research in Astronomy and Astrophysics (RAA) Journal

References in corpus (14)

• The Fourth US Naval Observatory CCD Astrograph Catalog (UCAC4)
• 9286 Stars: An Agglomeration of Stellar Polarization Catalogs
• Radiative torques: Analytical Model and Basic Properties
• Radiative Torques on Interstellar Grains: I. Superthermal Spinup
• Radiative Torques on Interstellar Grains: II. Grain Alignment
• The Efficiency of Grain Alignment in Dense Interstellar Clouds: A Reassessment of Constraints from Near Infrared Polarization
• Statistical Properties of Galactic Starlight Polarization
• Grain Alignment by Radiative Torques in Special Conditions and Implications
• The Polarizing Power of the Interstellar Medium in Taurus
• GRAIN ALIGNMENT IN THE TAURUS DARK CLOUD
• Large-scale magnetic fields in Bok globules
• A Study of starless dark cloud LDN 1570: Distance, Dust properties and Magnetic field geometry
• A method to determine distances to molecular clouds using near-IR photometry
• Study of background star polarization and polarization efficiency of three selected Bok globules CB56, CB60 and CB69

Cited by in corpus (3)

• Intensity-Corrected Herschel Observations of Nearby Isolated Low-Mass Clouds
• Study of magnetic field geometry and extinction in Bok globule CB130
• Distance estimation of some selected small Bok globules