Deep millimeter spectroscopy observations toward NGC 1068

Abstract

Aims. We aim for a better understanding of gas properties in the circum-nuclear disk (CND) region of the nearby gas-rich Seyfert 2 galaxy NGC 1068. We focus on line identification and the basic physical parameters estimation of molecular gas in the CND region. Methods. We used the IRAM 30 m telescope to conduct deep millimeter spectroscopy observations toward the center of NGC 1068. Results. Thirty-two lines were detected in this galaxy, 15 lines of wich were detected for the first time. With a sensitivity better by about a factor of 4 than observations in the literature for this source at 3 mm band, we detected several weak lines for the first time in this source, such as lines from CH3CCH, CH3OCH3, and HC18O+. Column densities of these molecules were estimated based on line emissions. Some marginal detections in the literature, such as HN13C (1–0), were confirmed. CH3OCH3 was detected for the first time in external galaxies. Lines from several carbon chain molecules and shock-related molecules were also detected in this source.