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Title: ORTHO-TO-PARA RATIO STUDIES OF SHOCKED H{sub 2} GAS IN THE TWO SUPERNOVA REMNANTS IC 443 AND HB 21

Abstract

We present near-infrared (2.5-5.0 {mu}m) spectral studies of shocked H{sub 2} gas in two supernova remnants, IC 443 and HB 21, which are well known for their interactions with nearby molecular clouds. The observations were performed with the Infrared Camera aboard the AKARI satellite. At the energy range 7000 K {approx}< E({upsilon},J) {approx}< 20,000 K, the shocked H{sub 2} gas in IC 443 shows an ortho-to-para ratio (OPR) of 2.4{sup +0.3} {sub -0.2}, which is significantly lower than the equilibrium value 3, suggesting the existence of non-equilibrium OPR. The shocked gas in HB 21 also indicates a potential non-equilibrium OPR in the range of 1.8-2.0. The level populations are well described by the power-law thermal admixture model with a single OPR, where the temperature integration range is 1000-4000 K. We conclude that the obtained non-equilibrium OPR probably originates from the reformed H{sub 2} gas of dissociative J-shocks, considering several factors such as the shock combination requirement, the line ratios, and the possibility that H{sub 2} gas can form on grains with a non-equilibrium OPR. We also investigate C-shocks and partially dissociative J-shocks as the origin of the non-equilibrium OPR. However, we find that they are incompatible with the observed ionicmore » emission lines for which dissociative J-shocks are required to explain. The difference in the collision energy of H atoms on grain surfaces would give rise to the observed difference between the OPRs of IC 443 and HB 21, if dissociative J-shocks are responsible for the H{sub 2} emission. Our study suggests that dissociative J-shocks can produce shocked H{sub 2} gas with a non-equilibrium OPR.« less

Authors:
;  [1];  [2]
  1. Korea Astronomy and Space Science Institute, 776 Daedeok-daero, Yuseong-gu, Daejeon 305-348 (Korea, Republic of)
  2. Department of Astronomy, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)
Publication Date:
OSTI Identifier:
22086477
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 759; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; ASTROPHYSICS; ATOM COLLISIONS; ATOMS; CAMERAS; EQUILIBRIUM; HYDROGEN; ION EMISSION; MOLECULES; PHOTON EMISSION; SATELLITES; SHOCK WAVES; SUPERNOVA REMNANTS

Citation Formats

Shinn, Jong-Ho, Moon, Dae-Sik, and Lee, Ho-Gyu, E-mail: jhshinn@kasi.re.kr, E-mail: hglee@astron.s.u-tokyo.ac.jp, E-mail: moon@astro.utoronto.ca. ORTHO-TO-PARA RATIO STUDIES OF SHOCKED H{sub 2} GAS IN THE TWO SUPERNOVA REMNANTS IC 443 AND HB 21. United States: N. p., 2012. Web. doi:10.1088/0004-637X/759/1/34.
Shinn, Jong-Ho, Moon, Dae-Sik, & Lee, Ho-Gyu, E-mail: jhshinn@kasi.re.kr, E-mail: hglee@astron.s.u-tokyo.ac.jp, E-mail: moon@astro.utoronto.ca. ORTHO-TO-PARA RATIO STUDIES OF SHOCKED H{sub 2} GAS IN THE TWO SUPERNOVA REMNANTS IC 443 AND HB 21. United States. doi:10.1088/0004-637X/759/1/34.
Shinn, Jong-Ho, Moon, Dae-Sik, and Lee, Ho-Gyu, E-mail: jhshinn@kasi.re.kr, E-mail: hglee@astron.s.u-tokyo.ac.jp, E-mail: moon@astro.utoronto.ca. Thu . "ORTHO-TO-PARA RATIO STUDIES OF SHOCKED H{sub 2} GAS IN THE TWO SUPERNOVA REMNANTS IC 443 AND HB 21". United States. doi:10.1088/0004-637X/759/1/34.
@article{osti_22086477,
title = {ORTHO-TO-PARA RATIO STUDIES OF SHOCKED H{sub 2} GAS IN THE TWO SUPERNOVA REMNANTS IC 443 AND HB 21},
author = {Shinn, Jong-Ho and Moon, Dae-Sik and Lee, Ho-Gyu, E-mail: jhshinn@kasi.re.kr, E-mail: hglee@astron.s.u-tokyo.ac.jp, E-mail: moon@astro.utoronto.ca},
abstractNote = {We present near-infrared (2.5-5.0 {mu}m) spectral studies of shocked H{sub 2} gas in two supernova remnants, IC 443 and HB 21, which are well known for their interactions with nearby molecular clouds. The observations were performed with the Infrared Camera aboard the AKARI satellite. At the energy range 7000 K {approx}< E({upsilon},J) {approx}< 20,000 K, the shocked H{sub 2} gas in IC 443 shows an ortho-to-para ratio (OPR) of 2.4{sup +0.3} {sub -0.2}, which is significantly lower than the equilibrium value 3, suggesting the existence of non-equilibrium OPR. The shocked gas in HB 21 also indicates a potential non-equilibrium OPR in the range of 1.8-2.0. The level populations are well described by the power-law thermal admixture model with a single OPR, where the temperature integration range is 1000-4000 K. We conclude that the obtained non-equilibrium OPR probably originates from the reformed H{sub 2} gas of dissociative J-shocks, considering several factors such as the shock combination requirement, the line ratios, and the possibility that H{sub 2} gas can form on grains with a non-equilibrium OPR. We also investigate C-shocks and partially dissociative J-shocks as the origin of the non-equilibrium OPR. However, we find that they are incompatible with the observed ionic emission lines for which dissociative J-shocks are required to explain. The difference in the collision energy of H atoms on grain surfaces would give rise to the observed difference between the OPRs of IC 443 and HB 21, if dissociative J-shocks are responsible for the H{sub 2} emission. Our study suggests that dissociative J-shocks can produce shocked H{sub 2} gas with a non-equilibrium OPR.},
doi = {10.1088/0004-637X/759/1/34},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 759,
place = {United States},
year = {2012},
month = {11}
}