Vibrationally Excited Lines of HC3N Associated with the Molecular Disk around the G24.78+0.08 A1 Hypercompact H ii Region
Journal article, 2022
We have analyzed Atacama Large Millimeter/submillimeter Array Band 6 data of the hypercompact H ii region G24.78+0.08 A1 (G24 HC H ii) and report the detection of vibrationally excited lines of HC3N (v (7) = 2, J = 24 - 23). The spatial distribution and kinematics of a vibrationally excited line of HC3N (v (7) = 2, J = 24 - 23, l = 2e) are found to be similar to the CH3CN vibrationally excited line (v (8) = 1), which indicates that the HC3N emission is tracing the disk around the G24 HC H ii region previously identified by the CH3CN lines. We derive the (CH3CN)-C-13/(HCCCN)-C-13 abundance ratios around G24 and compare them to the CH3CN/HC3N abundance ratios in disks around Herbig Ae and T Tauri stars. The (CH3CN)-C-13/(HCCCN)-C-13 ratios around G24 (similar to 3.0-3.5) are higher than the CH3CN/HC3N ratios in the other disks (similar to 0.03-0.11) by more than 1 order of magnitude. The higher CH3CN/HC3N ratios around G24 suggest that the thermal desorption of CH3CN in the hot dense gas and efficient destruction of HC3N in the region irradiated by the strong UV radiation are occurring. Our results indicate that the vibrationally excited HC3N lines can be used as a disk tracer of massive protostars at the HC H 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.
Author
Kotomi Taniguchi
National Astronomical Observatory of Japan
Kei E.I. Tanaka
National Astronomical Observatory of Japan
University of Colorado at Boulder
Yichen Zhang
University of Virginia
Rubén Fedriani
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Jonathan Tan
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
University of Virginia
Shigehisa Takakuwa
Academia Sinica
Kagoshima University
Fumitaka Nakamura
The Graduate University for Advanced Studies (SOKENDAI)
National Astronomical Observatory of Japan
University of Tokyo
Masao Saito
National Astronomical Observatory of Japan
The Graduate University for Advanced Studies (SOKENDAI)
Liton Majumdar
Homi Bhabha National Institute (HBNI)
National Institute of Science Education and Research
Eric Herbst
University of Virginia
Astrophysical Journal
0004-637X (ISSN) 1538-4357 (eISSN)
Vol. 931 2 99Eld ur is - den massiva stjärnbildningens utvecklingsstadier
Swedish Research Council (VR) (2017-04522), 2018-01-01 -- 2021-12-31.
Subject Categories
Astronomy, Astrophysics and Cosmology
Atom and Molecular Physics and Optics
Other Physics Topics
DOI
10.3847/1538-4357/ac69d1