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Measuring the Distribution and Excitation of Cometary CH3OH Using ALMA

Published online by Cambridge University Press:  27 October 2016

M. A. Cordiner ,
S. B. Charnley ,
M. J. Mumma ,
D. Bockelée-Morvan ,
N. Biver ,
G. Villanueva ,
L. Paganini ,
S. N. Milam ,
A. J. Remijan  and
D. C. Lis
...Show all authors
M. A. Cordiner
Affiliation:
NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA email: [email protected]
S. B. Charnley
Affiliation:
NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA email: [email protected]
M. J. Mumma
Affiliation:
NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA email: [email protected]
D. Bockelée-Morvan
Affiliation:
LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris-Diderot, Meudon, France
N. Biver
Affiliation:
LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris-Diderot, Meudon, France
G. Villanueva
Affiliation:
NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA email: [email protected]
L. Paganini
Affiliation:
NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA email: [email protected]
S. N. Milam
Affiliation:
NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA email: [email protected]
A. J. Remijan
Affiliation:
National Radio Astronomy Observatory, Charlottesville, VA 22903, USA
D. C. Lis
Affiliation:
LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, F-75014, Paris, France
J. Crovisier
Affiliation:
LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris-Diderot, Meudon, France
J. Boissier
Affiliation:
IRAM, 300 Rue de la Piscine, 38406 Saint Martin d'Heres, France
Y.-J. Kuan
Affiliation:
National Taiwan Normal University, Taipei 116, Taiwan, ROC
I. M. Coulson
Affiliation:
East Asian Observatory, Hilo 96720, USA
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Abstract

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The Atacama Large Millimeter/submillimeter Array (ALMA) was used to obtain measurements of spatially and spectrally resolved CH3OH emission from comet C/2012 K1 (PanSTARRS) on 28-29 June 2014. Detection of 12-14 emission lines of CH3OH on each day permitted the derivation of spatially-resolved rotational temperature profiles (averaged along the line of sight), for the innermost 5000 km of the coma. On each day, the CH3OH distribution was centrally peaked and approximately consistent with spherically symmetric, uniform outflow. The azimuthally-averaged CH3OH rotational temperature (Trot) as a function of sky-projected nucleocentric distance (ρ), fell by about 40 K between ρ= 0 and 2500 km on 28 June, whereas on 29 June, Trot fell by about 50 K between ρ =0 km and 1500 km. A remarkable (~50 K) rise in Trot at ρ = 1500-2500 km on 29 June was not present on 28 June. The observed variations in CH3OH rotational temperature are interpreted primarily as a result of variations in the coma kinetic temperature due to adiabatic cooling, and heating through Solar irradiation, but collisional and radiative non-LTE excitation processes also play a role.

Keywords

Comets: individual (C/2012 K1 (PanSTARRS)techniques: interferometricsubmillimetermolecular processes
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 11 , General Assembly A29A: Astronomy in Focus , August 2015 , pp. 233 - 236
Copyright
Copyright © International Astronomical Union 2016 

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