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Evidence for the Evolution of Grain Properties in the NGC 2024 Star Forming RidgeHigh-resolution images of the NGC 2024 molecular ridge in CS(2-1) and 3 mm continuum emission have been obtained using the Owens Valley millimeter array. The data are used to determine the temperature and dynamics of the ridge, and to ascertain the evolutionary state of the embedded protostars FIR2-7. Dust continuum emission is detected from all six FIR sources. The CS(2-1) follows the ridge closely, but does not always coincide with the FIR sources. Direct comparison of column density estimates derived from the CS and the dust emission in the ridge shows that for all FIR sources except FIR5 both methods are in agreement to within a factor of two, assuming a dust opacity k(sub 3 mm) = 0.01 cm(exp 2)/g. However, away from the FIR sources strong CS(1-0) emission is observed in several compact clumps which, with the above dust opacity, should have been detected in 3 mm dust continuum. The brightness temperature of the CS, approx. 40 K, rules out the possibility that the high line-to-continuum ratio is due to low gas temperatures; the discrepancy can be resolved if k(sub 3 mm) is a factor of 10 lower away from the FIR sources. A new high-resolution image of the 450-micron dust continuum emission obtained using the James Clerk Maxwell Telescope supports this hypothesis. These results suggest an evolution in the physical properties of the dust grains, possibly grain size, between quiescent regions in the ridge and the sites of active star formation.
Document ID
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Chandler, C. J.
(Cambridge Univ. Cambridge, United Kingdom)
Carlstrom, J. E.
(Chicago Univ. Chicago, IL United States)
Richer, J. S.
(Cambridge Univ. Cambridge, United Kingdom)
Visser, A.
(Cambridge Univ. Cambridge, United Kingdom)
Padman, R.
(Cambridge Univ. Cambridge, United Kingdom)
Date Acquired
August 17, 2013
Publication Date
October 1, 1996
Publication Information
Publication: From Stardust to Planetesimals: Contributed Papers
Subject Category
Accession Number
Funding Number(s)
Distribution Limits
Work of the US Gov. Public Use Permitted.
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