ALMA multiline observations toward the central region of NGC 613

作者：Miyamoto Yusuke^*; Nakai Naomasa; Seta Masumichi; Salak Dragan; Nagai Makoto; Kaneko Hiroyuki

来源：Publications of the Astronomical Society of Japan, 2017, 69(5): 83.

DOI：10.1093/pasj/psx076

• galaxies: active
• galaxies: individual (NGC 613)
• galaxies: ISM
• ISM: molecules
• radio lines: galaxies

We report ALMA observations of molecular gas and continuum emission in the 90 and 350 GHz bands toward a nearby Seyfert galaxy, NGC 613. Radio continuum emissions were detected at 95 and 350 GHz from both the circumnuclear disk (CND) (r less than or similar to 90 pc) and a star-forming ring (250 less than or similar to r less than or similar to 340 pc), and the 95 GHz continuum was observed to extend from the center at a position angle of 20 degrees +/- 8 degrees. The archival 4.9 GHz data and our 95 GHz data show spectral indices of alpha less than or similar to -0.6 and -0.2 alongthe jets and in the star-forming ring; these can be produced by synchrotron emission and free-free emission, respectively. In addition, we detected the emission of CO(3-2), HCN(1-0), HCN(4-3), HCO+(1-0), HCO+(4-3), CS(2-1), and CS(7-6) in both the CND and the ring. The rotational temperatures and column densities of molecules derived from J = 1-0 and 4-3 lines of HCN and HCO+ and J = 2-1 and 7-6 of CS in the CND and ring were derived. Furthermore, a non-local thermodynamic equilibrium model revealed that the kinetic temperature of T-k = 350-550 K in the CND is higher than T-k = 80-300 K in the ring, utilizing the intensity ratios of HCN, HCO+, and CS. The star-formation efficiency in the CND is almost an order of magnitude lower than those at the spots in the star-forming ring, while the dominant activity of the central region is star formation rather than active galactic nuclei. We determined that the large velocity dispersion of CO extending towards the north side of the CND and decomposing into blueshifted and redshifted features is probably explained by the effect of the radio jets. These results strongly suggest that the jets heat the gas in the CND, in which the feedback prevents star formation.

• 出版日期2017-10