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Record 1 of 2587
Polarimetry of the Interstellar Medium
Author and Affiliation:
Sandford, Scott(NASA Ames Research Center, Moffett Field, CA United States)
Witteborn, Fred C. [Technical Monitor]
Abstract: The talk will review what is known about the composition of ices and organics in the dense and diffuse interstellar media (ISM). Mixed molecular ices make up a significant fraction of the solid materials in dense molecular clouds and it is now known that thermal and radiation processing of these ices results in the production of more complex organic species, some of which may survive transport into forming stellar systems and the diffuse ISM. Molecular species identified in interstellar ices include H2O, CH3OH, CO, CH4, CO2, and somewhat surprisingly, H2. Theoretical and laboratory studies of the processing of interstellar analog ices containing these species indicate that species like HCO, H2CO, CH3, and NH3 are readily made and should also be present. The irradiation of mixed molecular ices containing these species, when followed by warming, leads to the production of a large variety of more complex species, including ethanol (CH3CH2OH), formamide (HC(=O)NH2), acetamide (CH3C(=O)NH2), nitriles or isonitriles (R-CN or R-NC hexamethylenetetramine (HMT; C6H12N4), a number of polymeric species related to polyoxymethylene [POM,(-CH2O-)n], and ketones {R-C(=O)-R'}. Spectral studies of dust in the diffuse ISM indicate the presence of fairly complex organics, some of which may be related to the organics produced in dense molecular clouds. Spectral comparisons indicate that the diffuse ISM organics may be quite similar to meteoritic kerogens, i.e. they may consist largely of aromatic moieties interlinked by short aliphatic bridges. Interestingly, recent evidence indicates that the galactic distribution of this material closely matches that of silicates, but does not correlate directly with visual extinction. This implies that a large fraction of the visual extinction is caused by a material other than these organics and silicates and that this other material has a significantly different distribution within the galaxy.
Publication Date: Jan 01, 1995
Document ID:
(Acquired Apr 05, 2002)
Subject Category: ASTROPHYSICS
Document Type: Preprint
Meeting Information: Polarimetry of the Interstellar Medium Meeting; 4-7 Jun. 1995; Troy, NY; United States
Contract/Grant/Task Num: RTOP 452-22-94
Financial Sponsor: NASA Ames Research Center; Moffett Field, CA United States
Organization Source: NASA Ames Research Center; Moffett Field, CA United States
Description: 1p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: No Copyright
Availability Source: Other Sources
Availability Notes: Abstract Only
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