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Paper: Dense Molecular Gas and Star Formation in Nearby Seyfert Galaxies
Volume: 249, The Central Kiloparsec of Starbursts and AGN: the La Palma Connection
Page: 672
Authors: Kohno, K.; Matsushita, S.; Vila-VilarĂ³, B.; Okumura, S. K.; Shibatsuka, T.; Okiura, M.; Ishizuki, S.; Kawabe, R.
Abstract: An imaging survey of CO (1 --> 0), HCN (1 --> 0), and HCO+ (1 --> 0) lines in the centers of nearby Seyfert galaxies has been conducted using the Nobeyama Millimeter Array and the RAINBOW interferometer. Preliminary results reveal that three Seyferts out of seven show abnormally high HCN/CO and HCO/HCO+ ratios, which cannot occur even in nuclear starburst galaxies. We suggest that the enhanced HCN emission could originate from X-ray-irradiated dense obscuring tori, and that these molecular line ratios can be a new diagnostic tool to search for ``pure'' AGN. According to our HCN diagram, we suggest that NGC 1068, NGC 1097, and NGC 5194 could host a ``pure'' AGN, whereas the Seyfert nuclei of NGC 3079, NGC 6764, and NGC 7469 may have a ``composite'' nature. We are indebted to the NRO staff for the effort in improving the performance of the array.
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