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Title: Grain alignment in starless cores

We present near-IR polarimetry data of background stars shining through a selection of starless cores taken in the K band, probing visual extinctions up to A{sub V}∼48. We find that P{sub K}/τ{sub K} continues to decline with increasing A{sub V} with a power law slope of roughly −0.5. Examination of published submillimeter (submm) polarimetry of starless cores suggests that by A{sub V}≳20 the slope for P versus τ becomes ∼−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{sub V}∼20. A simple model relating the alignment efficiency to the optical depth into the cloud reproduces the observations well.
Authors:
;  [1] ;  [2] ;  [3] ;  [4]
  1. Minnesota Institute for Astrophysics, University of Minnesota, Minneapolis, MN 55455 (United States)
  2. Cree Inc., 4600 Silicon Dr., Durham, NC (United States)
  3. SOFIA Science Center, USRA, Moffett Field, CA (United States)
  4. Centre de recherche en astrophysique du Québec and Départment de Physique, Université de Montréal, Montréal (Canada)
Publication Date:
OSTI Identifier:
22342157
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (New York, N.Y. Online); Journal Volume: 149; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALIGNMENT; DUSTS; EFFICIENCY; MAGNETIC FIELDS; NEAR INFRARED RADIATION; POLARIMETRY; RADIATION SOURCES; STARS