Grain alignment in starless cores
- Minnesota Institute for Astrophysics, University of Minnesota, Minneapolis, MN 55455 (United States)
- Cree Inc., 4600 Silicon Dr., Durham, NC (United States)
- SOFIA Science Center, USRA, Moffett Field, CA (United States)
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.
- OSTI ID:
- 22342157
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Vol. 149, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
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