The Cosmochemistry of Protostellar Matter

Abstract

The different processes that can affect the chemical composition of matter as it evolves from quiescent molecular clouds into protostellar regions is discussed. Millimeter observations of molecules at high angular resolution in cold, dark clouds such as TMC-1 and L134N reveal large chemical gradients on scales of a few tenths of a pc, which are not well understood. Further, the abundances of the dominant oxygen- (H_2O, O_2, O), and nitrogen-bearing (N_2, N) species are ill determined, both observationally and theoretically, and little is known about some important carbon-bearing molecules such as CH_4, CO_2 and C_2H_2 . Observations of the distribution of molecular material in disks surrounding newly-formed low-mass stars such as IRAS 16293 -2422 are just starting to become available, and reveal a complex chemistry on scales of 500-10,000 AU. Remarkable similarities are found with the chemistry observed in the highmass star forming region Orion/KL, despite a factor of 1000 difference in stellar luminosity. A brief comparison with the chemical composition comets is made.

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