Mathematics – Logic
Scientific paper
Oct 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999alma.confe..50q&link_type=abstract
Science with the Atacama Large Millimeter Array (ALMA), Associated Universities, Inc., held October 6-8, 1999 at Carnegie Instit
Mathematics
Logic
T Tauri, Herbig Ae, Stars, Ovro, Co, Hcn, C-, N-, O-, S-, Disk Rotation, Gas, Comets
Scientific paper
We are conducting an intensitve multi-species imaging study of two T Tauri and two Herbig Ae stars with the Owens Valley Millimeter Array. Interferometric images of several species in each of the important chemical families (C-, N-, O-, and S-bearing), including a number of isotopic variants, have been acquired. Even at moderate resolution (5") there appear to be interesting morphological differences between species expected to follow different (photo)chemical paths. The HCN velocity structure is similar to that seen in CO(2-1) showing that HCN participates in the same disk rotation. The integrated intensity map of HCN, however, shows a double peaked morphology suggestive of depletion of HCN in the inner disk. The H13CO+ emission provides an important lower bound to the gas fractional ionization of a few 10-10. The first detection of DCN in this kind of object has made possible a determination of the critical D/H ratio (DCN/HCN) in the circumstellar gas. At present, the data provides an approximate value of the D/H ratio of 0.01 since even H13CN(1-0) is optically thick, judging by its three hyperfine components. Still, this very high D/H ratio is comparable to those in comets, and suggests an evolutionary history in which cometary materials remain at very low temperatures throughout their assemblage and for the bulk of their lives.
Blake Geoffrey A.
Qi Charlie
Sargent Anneila I.
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