DCN in the 50 km/s Galactic Center Sgr A Molecular Cloud: Confirmation of the existence of deuterium in the Galactic Center

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Session 116 -- Galactic Center and Diffuse Galactic Emission
Oral presentation, Saturday, January 15, 10:15-11:45, Salon IV Room (Crystal Gateway)

[116.08] DCN in the 50 km/s Galactic Center Sgr A Molecular Cloud: Confirmation of the existence of deuterium in the Galactic Center

D. A. Lubowich ( Hofstra U. and AIP), Jay M. Pasachoff (Cfa and Williams), Thomas J. Balonek, Christy P. Tremonti (Colgate U.), Robert P. Galloway (Williams), Ann Mancuso (Hofstra U.)

We confirm the presence of deuterium in the Galactic Center Sgr A cloud (tentative detection by Penzias (ApJ, 228, 430, 1979) with T$_a^*$ = 0.02 Kq 0.15 K) by observing the 1-0 and 2-1 lines of DCN in the "50 km/s" Galactic Center molecular cloud (M-0.02-.07) using the NRAO 12-m telescope. We used the 3-mm and 2-mm SIS receivers in position switching mode with 1 MHz filters, 256 MHz bandwidth, 4.1 km/s resolution at the DCN 1-0 transition, and a typical T sys = 400K. We observed a Gaussian line peak intensity T$_r^*$ and integrated Gaussian intensity of 0.061 Kq.007 K, 2.0 K-km/s; and 0.042 Kq.02 K, 0.91 K-km/s for the optically thin 1-0 and 2-1 DCN lines, respectively. The DCN was concentrated along the north-south ridge observed in other molecules in this cloud. We also observed H13CN, HC15N, HNC, DNC and HCO+ at the position of the DCN 1-0 peak. From the DCN/H13CN we estimate DCN/HCN = .005. The inferred D/H is estimated to be less than the local ISM value of 2 x 10$^{-5}$, but is sensitive to the chemistry and physical conditions in the molecular cloud. These results imply that deuterated molecules D are not significantly enhanced in the GC molecular clouds and is consistant with the upper limits for atomic D obtained for the GC molecular clouds (Lubowich, Anantharamaiah, and Pasachoff, ApJ, 345, 770, 1989). The DCN/HCN we obtained is similar to that of the hot core of Orion so that D might be enhanced by fractionation and the sublimation of fossil D from grains. If there are no Galactic sources of D, then each generation of stars reduces the ISM D/H via astration and the observed D is the primordial abundance reduced by astration and mixing and possibly enhanced by the infall of primordial matter. If the rate of astration is faster in the GC as suggested by models of chemical evolution, then infall of primordial matter is a likely source of the GC deuterium.

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