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Spatial Separation of Molecular Conformers and Clusters
Published on: January 9, 2014
Shock chemistry in the molecular clouds associated with SNR IC 443
L M Ziurys1, R L Snell, R L Dickman
1Five College Radio Astronomy Observatory, University of Massachusetts, USA.
The Astrophysical Journal
|June 15, 1989
Summary
Interstellar molecules in IC 443 reveal hot, dense gas and shocks. Contrary to previous studies, molecule abundances like HCO+ are only slightly enhanced, except for SiO, which shows a significant increase, supporting high-temperature chemistry models.
Area of Science:
- Interstellar Chemistry
- Astrophysical Shocks
- Supernova Remnants
Background:
- IC 443 is a supernova remnant containing perturbed molecular clouds B and G.
- Previous studies suggested significant molecular abundance enhancements in these regions.
Purpose of the Study:
- Investigate the physical conditions and molecular abundances in the perturbed clouds of IC 443.
- Determine the impact of shocks on interstellar molecule formation and abundance.
Main Methods:
- Observation of 3 mm and 1.2 mm transitions of various interstellar molecules (N2H+, SiO, SO, CN, HNC, H13CO+, NH3, HCO+).
- Analysis of ammonia (NH3) inversion lines to determine gas kinetic temperatures.
- Modeling of HCO+ transitions to estimate gas densities.
- Comparison of observed abundances with predictions from low- and high-temperature chemistry models.
Main Results:
- Detection of hot (TK = 70 K in cloud B, 33 K in cloud G) and dense (nH > 10^5 cm^-3) gas in IC 443.
- HCO+ and N2H+ abundances are only slightly enhanced (factors of a few) compared to cold, quiescent gas, contradicting prior claims.
- SiO abundance is significantly enhanced (~100 times) in the perturbed gas, consistent with high-temperature chemistry.
- The HNC/HCN ratio (~0.1) suggests elevated temperatures, deviating from low-temperature ion-molecule chemistry predictions.
Conclusions:
- The perturbed clouds in IC 443 harbor hot, dense gas, likely influenced by shocks.
- The chemistry in these shocked regions is complex, with some species (SiO) showing high-temperature enhancements while others (HCO+, N2H+) do not.
- Observed molecular ratios provide crucial insights into the temperature and ionization conditions within supernova remnant environments.
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