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Observations of Two Non-Standard Grain ComponentsWe discuss evidence for two non-standard grain components: small conglomerates and astronomical iron. The small conglomerates are small, temperature fluctuating grains made up of loosely bound 12 micron emitters (either PAH's or dielectrics). When these grains are exposed to strong UV radiation fields they break apart into smaller pieces. For high UV radiation regimes, such as H II regions, conglomerate grains best explain the reduction of 25 micron emission relative to 12 micron. Astronomical iron was originally proposed for isolated cirrus clouds in order to account for the strength of the 60 micron emission. Within the diffuse ISM, these grains emit at a relatively high equilibrium temperature of 50 K. Our analysis of IRAS data shows the presence of a strong 60 micron emitter in the Lambda Orionis H II region and a component within the Rosette Nebula emitting primarily at 25 micron. Both of these observations can be accommodated by the presence of iron grains within the H II regions.
Document ID
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Shipman, R. F.
(Phillips Lab. Hanscom AFB, MA United States)
Carey, Sean J.
(Phillips Lab. Hanscom AFB, MA United States)
Clark, F. O.
(Phillips Lab. Hanscom AFB, MA United States)
Date Acquired
August 17, 2013
Publication Date
October 1, 1996
Publication Information
Publication: From Stardust to Planetesimals: Contributed Papers
Subject Category
Accession Number
Distribution Limits
Work of the US Gov. Public Use Permitted.
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