Bok globule CB 17: polarization, extinction and distance

Abstract

Abstract In this article, the results obtained from a polarimetric study of Bok globule CB 17 in both optical and submillimetre wavelengths are presented. Optical polarimetric observations in the R band (λ = 630 nm, Δλ = 120 nm) were conducted with the 1.04-m Sampurnanand Telescope, Aryabhatta Research Institute of observational sciencES (ARIES), in Nainital, India on 2016 March 9, while submillimetre polarimetric data are taken from the Submillimetre Common-User bolometer array POLarimeter (SCUPOL) data archive, which has been reanalysed. The contours of Herschel1 Spectral and Photometric Imaging Receiver (SPIRE) 500-μm dust continuum emission of CB 17 (typically a cometary-shaped globule) are overlaid on the Digital Sky Survey (DSS) image of CB 17 along with polarization vectors (optical and submm). The magnetic field strength at the core of the globule is estimated to be 99 μG. Using near-infrared photometric technique and Gaia data, the distance to CB 17 is found to be 253 ± 43 pc. The correlation between the various quantities of the globule is also studied. It is observed that the magnetic field in the cloud core as revealed by polarization measurements of the submillimetre dust emission is found to be almost aligned along the minor axis of the globule, which fits the magnetically regulated star formation model. A misalignment between core-scale magnetic field direction and molecular outflow direction is also found.