Grain Alignment in Starless Cores

T. J. Jones; M. Bagley; M. Krejny; B-G Anderson; P. Bastien

doi:10.1088/0004-6256/149/1/31

paper

Grain Alignment in Starless Cores

arXiv:1411.1031 · doi:10.1088/0004-6256/149/1/31

Abstract

We present near infrared polarimetry data of background stars shining through a selection of starless cores taken in the $K$ band, probing visual extinctions up to $A_{V} \sim 48$ . We find that $P_{K} / τ_{K}$ continues to decline with increasing $A_{V}$ with a power law slope of roughly -0.5. Examination of published submillimeter (submm) polarimetry of starless cores suggests that by $A_{V} ≳ 20$ the slope for $P$ vs. $τ$ becomes $\sim - 1$ , indicating no grain alignment at greater optical depths. Combining these two data sets, we find good evidence that, in the absence of a central illuminating source, the dust grains in dense molecular cloud cores with no internal radiation source cease to become aligned with the local magnetic field at optical depths greater than $A_{V} \sim 20$ . A simple model relating the alignment efficiency to the optical depth into the cloud reproduces the observations well.

33 pages, 5 figures

Grain Alignment in Starless Cores

Abstract

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