Mapping the release of volatiles in the inner comae of comets C/2012 f6 (LEMMON) and c/2012 s1 (ISON) using the Atacama large millimeter/Submillimeter array

M. A. Cordiner, A. J. Remijan, J. Boissier, S. N. Milam, M. J. Mumma, S. B. Charnley, L. Paganini, G. Villanueva, D. Bockelée-Morvan, Y. J. Kuan, Y. L. Chuang, D. C. Lis, N. Biver, J. Crovisier, D. Minniti, I. M. Coulson

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42 引文 斯高帕斯(Scopus)

摘要

Results are presented from the first cometary observations using the Atacama Large Millimeter/Submillimeter Array (ALMA), including measurements of the spatially resolved distributions of HCN, HNC, H2CO, and dust within the comae of two comets: C/2012 F6 (Lemmon) and C/2012 S1 (ISON), observed at heliocentric distances of 1.5 AU and 0.54 AU, respectively. These observations (with angular resolution 0.″5), reveal an unprecedented level of detail in the distributions of these fundamental cometary molecules, and demonstrate the power of ALMA for quantitative measurements of the distributions of molecules and dust in the inner comae of typical bright comets. In both comets, HCN is found to originate from (or within a few hundred kilometers of) the nucleus, with a spatial distribution largely consistent with spherically symmetric, uniform outflow. By contrast, the HNC distributions are clumpy and asymmetrical, with peaks at cometocentric radii 500-1000 km, consistent with release of HNC in collimated outflow(s). Compared to HCN, the H2CO distribution in comet Lemmon is very extended. The interferometric visibility amplitudes are consistent with coma production of H2CO and HNC from unidentified precursor material(s) in both comets. Adopting a Haser model, the H2CO parent scale length is found to be a few thousand kilometers in Lemmon and only a few hundred kilometers in ISON, consistent with the destruction of the precursor by photolysis or thermal degradation at a rate that scales in proportion to the solar radiation flux.

原文英語
文章編號L2
期刊Astrophysical Journal Letters
792
發行號1
DOIs
出版狀態已發佈 - 2014 九月 1

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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