科研之友
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摘要
It is important to investigate the relationships between the power sources and the chemical compositions of galaxies in order to understand the scenario of galaxy evolution. We carried out an unbiased molecular line survey towards active galactic nucleus (AGN) host galaxy NGC1068, and prototypical starburst galaxies, NGC253 and IC342, with the Nobeyama 45 m telescope in the 3 mm band. The advantage of this line survey is that the obtained spectra have the highest angular resolution ever obtained with single-dish telescopes. In particular, the beam size of this telescope is similar to 15 ''-19 '', which is able to separate spatially the nuclear molecular emission from that of the starburst ring (d similar to 30 '') in NGC1068. We successfully detected approximately 23 molecular species in each galaxy, and calculated rotation temperatures and column densities. We estimate the molecular fractional abundances with respect to (CO)-C-13 and CS molecules and compare them among three galaxies in order to investigate the chemical signatures of an AGN environment. As a result, we found clear trends in the abundances of molecules surrounding the AGN on a 1-kpc scale. HCN, (HCN)-C-13, CN, (CN)-C-13, and HC3N are more abundant, and CH3CCH is deficient in NGC1068 compared with the starburst galaxies. High abundances of HCN, (HCN)-C-13, and HC3N suggest that the circumnuclear disk in NGC1068 is in a high-temperature environment. The reason for the non-detection of CH3CCH is likely to be dissociation by high-energy radiation or less sublimation of a precursor of CH3CCH from grains.
- 出版日期2018-1
- 单位中国科学院国家天文台
