http://arxiv.org/abs/2204.09907
We have analyzed Atacama Large Millimeter/submillimeter Array Band 6 data of the hyper-compact H${\rm {II}}$ region G24.78+0.08 A1 (G24 HC H${\rm {II}}$) and report the detection of vibrationally-excited lines of HC${3}$N ($v{7}=2$, $J=24-23$). The spatial distribution and kinematics of a vibrationally-excited line of HC${3}$N ($v{7}=2$, $J=24-23$, $l=2e$) are found to be similar to the CH${3}$CN vibrationally-excited line ($v{8}=1$), which indicates that the HC${3}$N emission is tracing the disk around the G24 HC H${\rm {II}}$ region previously identified by the CH${3}$CN lines. We derive the $^{13}$CH${3}$CN/HC$^{13}$CCN abundance ratios around G24 and compare them to the CH${3}$CN/HC${3}$N abundance ratios in disks around Herbig Ae and T Tauri stars. The $^{13}$CH${3}$CN/HC$^{13}$CCN ratios around G24 ($\sim 3.0-3.5$) are higher than the CH${3}$CN/HC${3}$N ratios in the other disks ($\sim 0.03-0.11$) by more than one order of magnitude. The higher CH${3}$CN/HC${3}$N ratios around G24 suggest that the thermal desorption of CH${3}$CN in the hot dense gas and efficient destruction of HC${3}$N in the region irradiated by the strong UV radiation are occurring. Our results indicate that the vibrationally-excited HC${3}$N lines can be used as a disk tracer of massive protostars at the HC H$_{\rm {II}}$ region stage, and the combination of these nitrile species will provide information of not only chemistry but also physical conditions of the disk structures.
K. Taniguchi, K. Tanaka, Y. Zhang, et. al.
Fri, 22 Apr 22
32/64
Comments: 21 pages, 13 figures, 5 tables, Accepted by The Astrophysical Journal
You must be logged in to post a comment.