Molecular spectroscopy; High resolution spectroscopy; Radio astronomy; Comets
Abstract :
[en] We report the detection of CH3OH emission in comet 46P/Wirtanen on UT 2018 December 8 and 9 using the Atacama Compact Array (ACA), part of the Atacama Large Millimeter/Submillimeter Array (ALMA). These interferometric measurements of CH3OH along with continuum emission from dust probed the inner coma (<2000 km from the nucleus) of 46P/Wirtanen approximately one week before its closest approach to Earth (Δ = 0.089-0.092 au), revealing rapidly varying and anisotropic CH3OH outgassing during five separate ACA executions between UT 23:57 December 7 and UT 04:55 December 9, with a clear progression in the spectral line profiles over a timescale of minutes. We present spectrally integrated flux maps, production rates, rotational temperatures, and spectral line profiles of CH3OH during each ACA execution. The variations in CH3OH outgassing are consistent with Wirtanen's 9 hr nucleus rotational period derived from optical and millimeter wavelength measurements and thus are likely coupled to the changing illumination of active sites on the nucleus. The consistent blue offset of the line center indicates enhanced CH3OH sublimation from the sunward hemisphere of the comet, perhaps from icy grains. These results demonstrate the exceptional capabilities of the ACA for time-resolved measurements of comets such as 46P/Wirtanen.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Roth, Nathan X.; Visiting Astronomer at the Infrared Telescope Facility, which is operated by the University of Hawaii under contract NNH14CK55B with the National Aeronautics and Space Administration. ; Solar System Exploration Division, Astrochemistry Laboratory Code 691, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA ; Universities Space Research Association, Columbia, MD 21046, USA
Milam, Stefanie N.; Solar System Exploration Division, Astrochemistry Laboratory Code 691, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA
Cordiner, Martin A.; Solar System Exploration Division, Astrochemistry Laboratory Code 691, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA ; Department of Physics, Catholic University of America, Washington DC, USA
Bockelée-Morvan, Dominique; LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, F-92195 Meudon, France
DiSanti, Michael A.; Visiting Astronomer at the Infrared Telescope Facility, which is operated by the University of Hawaii under contract NNH14CK55B with the National Aeronautics and Space Administration. ; Solar System Exploration Division, Planetary Systems Laboratory Code 693, NASA-GSFC, Greenbelt, MD 20771, USA
Boissier, Jérémie; Institut de Radioastronomie Millimetrique, 300 rue de la piscine, F-38406 Saint Martin d'Heres, France
Biver, Nicolas; LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, F-92195 Meudon, France
Crovisier, Jacques; LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, F-92195 Meudon, France
Russo, Neil Dello; Visiting Astronomer at the Infrared Telescope Facility, which is operated by the University of Hawaii under contract NNH14CK55B with the National Aeronautics and Space Administration. ; Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD, 20723 USA
Bonev, Boncho P.; Visiting Astronomer at the Infrared Telescope Facility, which is operated by the University of Hawaii under contract NNH14CK55B with the National Aeronautics and Space Administration. ; Department of Physics, American University, 4400 Massachusetts Avenue, NW Washington, DC 20016 USA
Qi, Chunhua; Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Mail Stop 42 Cambridge, MA 02138, USA
Remijan, Anthony J.; National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA
Charnley, Steven B.; Solar System Exploration Division, Astrochemistry Laboratory Code 691, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA
Gibb, Erika L.; Visiting Astronomer at the Infrared Telescope Facility, which is operated by the University of Hawaii under contract NNH14CK55B with the National Aeronautics and Space Administration. ; Department of Physics & Astronomy, University of Missouri-St.Louis, 1 University Boulevard, St. Louis, MO 63121 USA
Val-Borro, Miguel De; Planetary Science Institute, 1700 E. Fort Lowell, Suite 106, Tucson, AZ 85719, USA
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