Detections of C2H, cyclic-C3H2, and H13CN in NGC 1068

Abstract

We used the Nobeyama 45-m telescope to conduct a spectral line survey in the 3-mm band (85.1-98.4 GHz) toward one of the nearest galaxies with active galactic nucleus NGC 1068 and the prototypical starburst galaxy NGC 253. The beam size of this telescope is ~18", which was sufficient to spatially separate the nuclear molecular emission from the emission of the circumnuclear starburst region in NGC 1068. We detected rotational transitions of C2H, cyclic-C3H2, and H13CN in NGC 1068. These are detections of carbon-chain and carbon-ring molecules in NGC 1068. In addition, the C2H N = 1-0 lines were detected in NGC 253. The column densities of C2H were determined to be 3.4 x 10^15 cm^-2 in NGC 1068 and 1.8 x 10^15 cm^-2 in NGC 253. The column densities of cyclic-C3H2 were determined to be 1.7 x 10^13 cm^-2 in NGC 1068 and 4.4 x 10^13 cm^-2 in NGC 253. We calculated the abundances of these molecules relative to CS for both NGC 1068 and NGC 253, and found that there were no significant differences in the abundances between the two galaxies. This result suggests that the basic carbon-containing molecules are either insusceptible to AGN, or are tracing cold (T_rot ~10 K) molecular gas rather than X-ray irradiated hot gas.

arXiv comment10 pages, 3 figures, Accepted for publication in ApJ Letter. After the submission of this manuscript, we found two relevant papers. Snell et al. detected C2H in NGC 1068 (astro-ph 1101.0132). It was very recently published in The Astronomical Journal 141 38. Costagliola et al. detected C2H and H13CN in NGC 1068 (astro-ph 1101.2122)

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• Modeling The Molecular Composition in an AGN Disk
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• Spectral Line Survey toward Spiral Arm of M51 in the 3 mm and 2 mm Bands
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• ALMA Observations of Warm Molecular Gas and Cold Dust in NGC 34
• A Multi-Transition Study of Molecules toward NGC 1068 based on High-Resolution Imaging Observations with ALMA
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• Modelling the Molecular Gas in NGC 6240
• ALMA observations of CS in NGC 1068: chemistry and excitation
• Molecular Distribution in the Spiral Arm of M51
• Chemistry in isolation: High CCH/HCO+ line ratio in the AMIGA galaxy CIG 638
• A 3 mm Spectral Line Survey toward the Barred Spiral Galaxy NGC 3627
• λ = 2 mm spectroscopy observations toward the circumnuclear disk of NGC 1068
• The influence of cosmic rays in the circumnuclear molecular gas of NGC1068