Constraining Volatile Abundances in Comet C/2004 Q2 (Machholz)
Abstract
Spectroscopic observations of comets provide an important tool to understand their chemical composition. We aim to determine the production rates of parent volatiles in comet C/2004 Q2 (Machholz). The line emission from several molecules in the cometary atmosphere is measured at heliocentric distance of 1.2 AU in January 2005 by means of high-resolution spectroscopic observations using the Heinrich Hertz Submillimeter Telescope. The measured relative abundances of several volatiles (CH3OH, HCN, HNC, H13CN, H2CO, CO, and CS) suggest a thermal processing history similar to Jupiter-family comets. We obtain production rates and excitation temperatures from simulations of the line profiles using a radiative transfer code based on the accelerated lambda iteration method. Furthermore, multiline observations of CH3OH allow for a rough estimate of the excitation temperature using the rotation diagram technique. We derive a rotational temperature of 37 ± 10 K for CH3OH and mixing ratios relative to HCN of CO/CH3OH/H2CO/HCN = 31/12/3/1.
- Publication:
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Advances in Geosciences, Volume 25: Planetary Science (PS)
- Pub Date:
- July 2011
- DOI:
- 10.1142/9789814355377_0011
- Bibcode:
- 2011aogs...25..149D