J/ApJ/727/91 Fluorescence excitation models in comets (Kawakita+, 2011)
Fluorescence excitation models of ammonia and amidogen radical (NH2) in
comets: application to comet C/2004 Q2 (Machholz).
Kawakita H., Mumma M.J.
<Astrophys. J., 727, 91 (2011)>
=2011ApJ...727...91K 2011ApJ...727...91K
ADC_Keywords: Comets ; Line Profiles ; Spectra, infrared
Keywords: comets: general - comets: individual (C/2004 Q2 (Machholz)) -
line: formation - line: identification
Abstract:
Ammonia is a major reservoir of nitrogen atoms in cometary materials.
However, detections of ammonia in comets are rare, with several
achieved at radio wavelengths. A few more detections were obtained
through near-infrared observations (around the 3um wavelength region),
but moderate relative velocity shifts are required to separate
emission lines of cometary ammonia from telluric absorption lines in
the 3um wavelength region. On the other hand, the amidogen radical
(NH2, a photodissociation product of ammonia in the coma) also shows
rovibrational emission lines in the 3um wavelength region. Thus, gas
production rates for ammonia can be determined from the rovibrational
emission lines of ammonia (directly) and amidogen radical (indirectly)
simultaneously in the near-infrared. In this article, we present new
fluorescence excitation models for cometary ammonia and amidogen
radical in the near-infrared, and we apply these models to the
near-infrared high-dispersion spectra of comet C/2004 Q2 (Machholz) to
determine the mixing ratio of ammonia to water in the comet. Based on
direct detection of NH3 lines, the mixing ratio of NH3/H2O is
0.46%±0.03% in C/2004 Q2 (Machholz), in agreement with other
results. The mixing ratio of ammonia determined from the NH2
observations (0.31%-0.79%) is consistent but has relatively larger
error, owing to uncertainty in the photodissociation rates of ammonia.
At the present level of accuracy, we confirm that NH3 could be the
sole parent of NH2 in this comet.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 61 61 The g-factors (fluorescence efficiencies) for lines
of NH3 ν1 at 1AU (dr/dt=0km/s)
table4b.dat 61 86 The g-factors (fluorescence efficiencies) for lines
of NH3 ν3 at 1AU (dr/dt=0km/s)
table5.dat 65 201 The g-factors of NH2 ν1 at 1AU (dr/dt=0km/s)
table5b.dat 65 197 The g-factors of NH2 ν3 at 1AU (dr/dt=0km/s)
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See also:
J/ApJ/703/121 : Spectroscopy of comet C/2004 Q2 (Machholz) (Kobayashi+, 2009)
J/ApJS/169/458 : Highly excited H2 in Comets (Liu+, 2007)
J/PAZh/30/946 : Unidentified cometary emission lines (Simonia, 2004)
J/AJ/112/1197 : Catalog of cometary emission lines (Brown+ 1996)
J/A+AS/103/83 : Line identifications in a fireball spectrum (Borovicka 1994)
Byte-by-byte Description of file: table4.dat table4b.dat
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Bytes Format Units Label Explanations
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1- 7 F7.2 cm-1 Wave Wavenumber
9- 16 E8.2 ph/s g20 The g-factor at 20K
18- 25 E8.2 ph/s g70 The g-factor at 70K
27- 34 E8.2 ph/s g100 The g-factor at 100K
36- 43 E8.2 ph/s g120 The g-factor at 120K
45- 52 E8.2 ph/s g150 The g-factor at 150K
54- 61 A8 --- Line Assignment: ν1 band for table4 or
ν3 band for table4b
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Byte-by-byte Description of file: table5.dat table5b.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 F7.2 cm-1 Wave Wavenumber
9- 16 E8.2 ph/s g20 The g-factor at 20K
18- 25 E8.2 ph/s g70 The g-factor at 70K
27- 34 E8.2 ph/s g100 The g-factor at 100K
36- 43 E8.2 ph/s g120 The g-factor at 120K
45- 52 E8.2 ph/s g150 The g-factor at 150K
54- 65 A12 --- Line Assignment ν1 band for table5 or
ν3 band for table5b (J'(Ka',Kc')--J"(Ka",Kc"))
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 30-Aug-2012