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D. A. Lubowich (Hofstra U,), N. Kuno (Nobeyama Radio Observatory), H. Roberts, T. J. Millar (U. of Manchester), C. Henkel (Max-Planck-Institut für Radioastronomie), J. M. Pasachoff (Williams College), R. Mauersberger (IRAM, Spain)
Although deuterium is predicted to be primarily cosmological, D can also be produced by cosmic-ray or \gamma-ray spallation reactions - possibly between high energy jets and the surrounding gas in AGN. We used the Nobeyama mm array with a 3” resolution (220 pc) in April 2003 to search for any enhanced D from the DCN J = 2-1 line in the Seyfert galaxy NGC 1068. NGC 1068 is an optimal target because it has jets, starburst activity, a circumuclear molecular ring and disk, dense optically thick concentrations of HCN, and a low-energy X-ray flux of 1042 erg/s (the highest X-ray flux of any galaxy in which HCN has been detected and the flux required to produce high D abundances). We did not detect DCN (which is detected in all other molecular clouds with optically thick HCN in the Galaxy or LMC) and we obtained an upper limit of S\leq15 mJy/beam = 48.5 mK in the circumnuclear region and a DCN/HCN ratio of 0.0046. Using our 5300 reaction chemical network we estimate D/H leq1.5x10-5 as compared to the local Galactic ISM D/H = 1.4x10-5.
Thus there is no significant D production in the nuclear region of NGC 1068 and NGC 1068 has probably not had a recent period of activity with a \gamma-ray or cosmic-ray luminosity > 1042 erg/s. If jet-cloud nucleosynthesis produces significant amounts of D, then the D is produced outside of the nuclear region where the subsequent infall may be one way to continuously supply galactic nuclei with D. However, any enhanced D produced via spallation reactions would have been destroyed via astration due to the faster star formation rate. Our results are additional evidence that D is primarily cosmological and that AGN do not produce D.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.