Thermal Physics of the Inner Coma

ALMA Studies of the Methanol Distribution and Excitation in Comet C/2012 K1 (PanSTARRS)

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

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

We present spatially and spectrally resolved observations of CH3OH emission from comet C/2012 K1 (PanSTARRS), using the Atacama Large Millimeter/submillimeter Array on 2014 June 28-29. Two-dimensional maps of the line-of-sight average rotational temperature (T rot) were derived, covering spatial scales 0.″3-1.″8 (corresponding to sky-projected distances ρ ∼ 500-2500 km). The CH3OH column density distributions are consistent with isotropic, uniform outflow from the nucleus, with no evidence for extended sources of CH3OH in the coma. The radial profiles show a significant drop within a few thousand kilometers of the nucleus, falling from about 60 to 20 K between and 2500 km on June 28, whereas on June 29, T rot fell from about 120 to 40 K between ρ = 0 km and 1000 km. The observed T rot behavior is interpreted primarily as a result of variations in the coma kinetic temperature due to adiabatic cooling of the outflowing gas, as well as radiative cooling of the CH3OH rotational levels. Our excitation model shows that radiative cooling is more important for the transitions (at 338 GHz) than for the transitions (at 252 GHz), resulting in a strongly sub-thermal distribution of levels in the band at . For both bands, the observed temperature drop with distance is less steep than predicted by standard coma theoretical models, which suggests the presence of a significant source of heating in addition to the photolytic heat sources usually considered.

Original languageEnglish
Article number177
JournalAstrophysical Journal
Volume837
Issue number2
DOIs
Publication statusPublished - 2017 Mar 10

Fingerprint

coma
comets
comet
methanol
physics
methyl alcohol
cooling
excitation
nuclei
temperature
heat source
heat sources
falling
line of sight
density distribution
sky
coverings
outflow
heating
kinetics

Keywords

  • Comets: individual (C/2012 K1, PanSTARRS)
  • molecular processes
  • techniques: imaging spectroscopy
  • techniques: interferometric

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Cordiner, M. A., Biver, N., Crovisier, J., Bockelée-Morvan, D., Mumma, M. J., Charnley, S. B., ... Boissier, J. (2017). Thermal Physics of the Inner Coma: ALMA Studies of the Methanol Distribution and Excitation in Comet C/2012 K1 (PanSTARRS). Astrophysical Journal, 837(2), [177]. https://doi.org/10.3847/1538-4357/aa6211

Thermal Physics of the Inner Coma : ALMA Studies of the Methanol Distribution and Excitation in Comet C/2012 K1 (PanSTARRS). / Cordiner, M. A.; Biver, N.; Crovisier, J.; Bockelée-Morvan, D.; Mumma, M. J.; Charnley, S. B.; Villanueva, G.; Paganini, L.; Lis, D. C.; Milam, S. N.; Remijan, A. J.; Coulson, I. M.; Kuan, Yi-Jehng; Boissier, J.

In: Astrophysical Journal, Vol. 837, No. 2, 177, 10.03.2017.

Research output: Contribution to journalArticle

Cordiner, MA, Biver, N, Crovisier, J, Bockelée-Morvan, D, Mumma, MJ, Charnley, SB, Villanueva, G, Paganini, L, Lis, DC, Milam, SN, Remijan, AJ, Coulson, IM, Kuan, Y-J & Boissier, J 2017, 'Thermal Physics of the Inner Coma: ALMA Studies of the Methanol Distribution and Excitation in Comet C/2012 K1 (PanSTARRS)', Astrophysical Journal, vol. 837, no. 2, 177. https://doi.org/10.3847/1538-4357/aa6211
Cordiner, M. A. ; Biver, N. ; Crovisier, J. ; Bockelée-Morvan, D. ; Mumma, M. J. ; Charnley, S. B. ; Villanueva, G. ; Paganini, L. ; Lis, D. C. ; Milam, S. N. ; Remijan, A. J. ; Coulson, I. M. ; Kuan, Yi-Jehng ; Boissier, J. / Thermal Physics of the Inner Coma : ALMA Studies of the Methanol Distribution and Excitation in Comet C/2012 K1 (PanSTARRS). In: Astrophysical Journal. 2017 ; Vol. 837, No. 2.
@article{c552dac3c0884b338b6ac613735cbd0d,
title = "Thermal Physics of the Inner Coma: ALMA Studies of the Methanol Distribution and Excitation in Comet C/2012 K1 (PanSTARRS)",
abstract = "We present spatially and spectrally resolved observations of CH3OH emission from comet C/2012 K1 (PanSTARRS), using the Atacama Large Millimeter/submillimeter Array on 2014 June 28-29. Two-dimensional maps of the line-of-sight average rotational temperature (T rot) were derived, covering spatial scales 0.″3-1.″8 (corresponding to sky-projected distances ρ ∼ 500-2500 km). The CH3OH column density distributions are consistent with isotropic, uniform outflow from the nucleus, with no evidence for extended sources of CH3OH in the coma. The radial profiles show a significant drop within a few thousand kilometers of the nucleus, falling from about 60 to 20 K between and 2500 km on June 28, whereas on June 29, T rot fell from about 120 to 40 K between ρ = 0 km and 1000 km. The observed T rot behavior is interpreted primarily as a result of variations in the coma kinetic temperature due to adiabatic cooling of the outflowing gas, as well as radiative cooling of the CH3OH rotational levels. Our excitation model shows that radiative cooling is more important for the transitions (at 338 GHz) than for the transitions (at 252 GHz), resulting in a strongly sub-thermal distribution of levels in the band at . For both bands, the observed temperature drop with distance is less steep than predicted by standard coma theoretical models, which suggests the presence of a significant source of heating in addition to the photolytic heat sources usually considered.",
keywords = "Comets: individual (C/2012 K1, PanSTARRS), molecular processes, techniques: imaging spectroscopy, techniques: interferometric",
author = "Cordiner, {M. A.} and N. Biver and J. Crovisier and D. Bockel{\'e}e-Morvan and Mumma, {M. J.} and Charnley, {S. B.} and G. Villanueva and L. Paganini and Lis, {D. C.} and Milam, {S. N.} and Remijan, {A. J.} and Coulson, {I. M.} and Yi-Jehng Kuan and J. Boissier",
year = "2017",
month = "3",
day = "10",
doi = "10.3847/1538-4357/aa6211",
language = "English",
volume = "837",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "2",

}

TY - JOUR

T1 - Thermal Physics of the Inner Coma

T2 - ALMA Studies of the Methanol Distribution and Excitation in Comet C/2012 K1 (PanSTARRS)

AU - Cordiner, M. A.

AU - Biver, N.

AU - Crovisier, J.

AU - Bockelée-Morvan, D.

AU - Mumma, M. J.

AU - Charnley, S. B.

AU - Villanueva, G.

AU - Paganini, L.

AU - Lis, D. C.

AU - Milam, S. N.

AU - Remijan, A. J.

AU - Coulson, I. M.

AU - Kuan, Yi-Jehng

AU - Boissier, J.

PY - 2017/3/10

Y1 - 2017/3/10

N2 - We present spatially and spectrally resolved observations of CH3OH emission from comet C/2012 K1 (PanSTARRS), using the Atacama Large Millimeter/submillimeter Array on 2014 June 28-29. Two-dimensional maps of the line-of-sight average rotational temperature (T rot) were derived, covering spatial scales 0.″3-1.″8 (corresponding to sky-projected distances ρ ∼ 500-2500 km). The CH3OH column density distributions are consistent with isotropic, uniform outflow from the nucleus, with no evidence for extended sources of CH3OH in the coma. The radial profiles show a significant drop within a few thousand kilometers of the nucleus, falling from about 60 to 20 K between and 2500 km on June 28, whereas on June 29, T rot fell from about 120 to 40 K between ρ = 0 km and 1000 km. The observed T rot behavior is interpreted primarily as a result of variations in the coma kinetic temperature due to adiabatic cooling of the outflowing gas, as well as radiative cooling of the CH3OH rotational levels. Our excitation model shows that radiative cooling is more important for the transitions (at 338 GHz) than for the transitions (at 252 GHz), resulting in a strongly sub-thermal distribution of levels in the band at . For both bands, the observed temperature drop with distance is less steep than predicted by standard coma theoretical models, which suggests the presence of a significant source of heating in addition to the photolytic heat sources usually considered.

AB - We present spatially and spectrally resolved observations of CH3OH emission from comet C/2012 K1 (PanSTARRS), using the Atacama Large Millimeter/submillimeter Array on 2014 June 28-29. Two-dimensional maps of the line-of-sight average rotational temperature (T rot) were derived, covering spatial scales 0.″3-1.″8 (corresponding to sky-projected distances ρ ∼ 500-2500 km). The CH3OH column density distributions are consistent with isotropic, uniform outflow from the nucleus, with no evidence for extended sources of CH3OH in the coma. The radial profiles show a significant drop within a few thousand kilometers of the nucleus, falling from about 60 to 20 K between and 2500 km on June 28, whereas on June 29, T rot fell from about 120 to 40 K between ρ = 0 km and 1000 km. The observed T rot behavior is interpreted primarily as a result of variations in the coma kinetic temperature due to adiabatic cooling of the outflowing gas, as well as radiative cooling of the CH3OH rotational levels. Our excitation model shows that radiative cooling is more important for the transitions (at 338 GHz) than for the transitions (at 252 GHz), resulting in a strongly sub-thermal distribution of levels in the band at . For both bands, the observed temperature drop with distance is less steep than predicted by standard coma theoretical models, which suggests the presence of a significant source of heating in addition to the photolytic heat sources usually considered.

KW - Comets: individual (C/2012 K1, PanSTARRS)

KW - molecular processes

KW - techniques: imaging spectroscopy

KW - techniques: interferometric

UR - http://www.scopus.com/inward/record.url?scp=85015855436&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85015855436&partnerID=8YFLogxK

U2 - 10.3847/1538-4357/aa6211

DO - 10.3847/1538-4357/aa6211

M3 - Article

VL - 837

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 2

M1 - 177

ER -