ALMA Autocorrelation Spectroscopy of Comets: The HCN/H13CN Ratio in C/2012 S1 (ISON)

M. A. Cordiner, M. Y. Palmer, M. De Val-Borro, S. B. Charnley, L. Paganini, G. Villanueva, D. Bockelée-Morvan, N. Biver, A. J. Remijan, Y. J. Kuan, S. N. Milam, J. Crovisier, D. C. Lis, M. J. Mumma

研究成果: 雜誌貢獻文章

1 引文 斯高帕斯(Scopus)

摘要

The Atacama Large Millimeter/submillimeter Array (ALMA) is a powerful tool for high-resolution mapping of comets, but the main interferometer (comprised of 50 × 12 m antennas) is insensitive to the largest coma scales due to a lack of very short baselines. In this Letter, we present a new technique employing ALMA autocorrelation data (obtained simultaneously with the interferometric observations), effectively treating the entire 12 m array as a collection of single-dish telescopes. Using combined autocorrelation spectra from 28 active antennas, we recovered extended HCN coma emission from comet C/2012 S1 (ISON), resulting in a fourteen-fold increase in detected line brightness compared with the interferometer. This resulted in the first detection of rotational emission from H13CN in this comet. Using a detailed coma radiative transfer model accounting for optical depth and non-local thermodynamic equilibrium excitation effects, we obtained an H12CN/H13CN ratio of 88 ±18, which matches the terrestrial value of 89. This is consistent with a lack of isotopic fractionation in HCN during comet formation in the protosolar accretion disk. The possibility of future discoveries in extended sources using autocorrelation spectroscopy from the main ALMA array is thus demonstrated.

原文英語
文章編號L26
期刊Astrophysical Journal Letters
870
發行號2
DOIs
出版狀態已發佈 - 2019 一月 10

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Cordiner, M. A., Palmer, M. Y., Val-Borro, M. D., Charnley, S. B., Paganini, L., Villanueva, G., Bockelée-Morvan, D., Biver, N., Remijan, A. J., Kuan, Y. J., Milam, S. N., Crovisier, J., Lis, D. C., & Mumma, M. J. (2019). ALMA Autocorrelation Spectroscopy of Comets: The HCN/H13CN Ratio in C/2012 S1 (ISON). Astrophysical Journal Letters, 870(2), [L26]. https://doi.org/10.3847/2041-8213/aafb05