http://arxiv.org/abs/1812.08920
We present the results based on the optical $R$-band polarization observations of 280 stars distributed towards the dark globule LDN 1225. Gaia data release 2 parallaxes along with the polarization data of $\sim$200 stars have been used to (a) constrain the distance of LDN 1225 to be 800$\pm$80 pc, (b) determine the contribution of interstellar polarization (ISP), and (c) characterize the dust properties and delineate the magnetic field (B-field) morphology of LDN 1225. We find that B-fields are more organized and exhibit a small dispersion of 12 degree. Using the $^{12}$CO molecular line data from the Purple Mountain Observatory (PMO), along with the column density, dispersion in B-fields, we estimate B-field strength to be 58$\pm$12 $\mu$G, magnetic to turbulence pressure to be 3$\pm$2, and the mass-to-magnetic flux ratio (in units of critical value) to be $<$ 1. These results indicate the dominant role of B-fields in comparison to turbulence and gravity in rendering the cloud support. B-fields are aligned parallel to the low-density parts (traced by $^{12}$CO map) of the cloud, in contrast they are neither parallel nor perpendicular to the high-density core structures (traced by $^{13}$CO and C$^{18}$O maps). LDN 1225 hosts two 70 $\mu$m sources which seem to be of low-mass Class 0 sources. The total-to-selective extinction derived using optical and near-infrared photometric data to be anomalous ($R_{V}$ = 3.6), suggesting dust grain growth in LDN 1225. Polarization efficiency of dust grains follows a power-law index of $-$0.7 inferring that optical polarimetry traces B-fields in the outer parts of the cloud.
C. Eswaraiah, S. Lai, Y. Ma, et. al.
Mon, 24 Dec 18
41/47
Comments: 30 Pages, 18 Figures, Submitted to ApJ. Comments are welcome
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