Infrared Studies of Molecular Shocks in the Supernova Remnant HB 21: II. Thermal Admixture of Shocked H${}_2$ Gas in the South

Abstract

We present near- and mid-infrared observations on the shock-cloud interaction region in the southern part of the supernova remnant HB 21, performed with the InfraRed Camera (IRC) aboard AKARI satellite and the Wide InfraRed Camera (WIRC) at the Palomar 5 m telescope. The IRC 4 um (N4), 7 um (S7), and 11 um (S11) band images and the WIRC H2 v=1->0 S(1) 2.12 um image show similar diffuse features, around a shocked CO cloud. We analyzed the emission through comparison with the H2 line emission of several shock models. The IRC colors are well explained by the thermal admixture model of H2 gas--whose infinitesimal H2 column density has a power-law relation with the temperature $T$, $dN\sim T^{-b}dT$--with n(H2) $\sim 3.9\times 10^4$ cm^{-2}, $b\sim 4.2$, and N(H2;T>100K) $\sim 2.8\times 10^{21}$ cm^{-2}. We interpreted these parameters with several different pictures of the shock-cloud interactions--multiple planar C-shocks, bow shocks, and shocked clumps--and discuss their weaknesses and strengths. The observed H2 v=1->0 S(1) intensity is four times greater than the prediction from the power-law admixture model, the same tendency as found in the northern part of HB 21 (Paper I). We also explored the limitation of the thermal admixture model with respect to the derived model parameters.

35 pages, 10 figures, Accepted in "Advances in Space Research", higher resolution @ http://astro.snu.ac.kr/~jhshinn/asr-20090921-submitted_arxiv.pdf ; rev.2 - deletion of section 6.4 and the related contents

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• AKARI Near-infrared Spectral Observations of Shocked H2 Gas of the Supernova Remnant IC 443
• Far-Infrared Luminous Supernova Remnant Kes 17
• Detection of 3.3 Micron Aromatic Feature in the Supernova Remnant N49 with AKARI
• Discovery of Broad Molecular lines and of Shocked Molecular Hydrogen from the Supernova Remnant G357.7+0.3: HHSMT, APEX, Spitzer and SOFIA Observations
• Ortho-to-Para Ratio Studies of Shocked H2 Gas in the Two Supernova Remnants IC 443 and HB 21
• Shocked Molecular Hydrogen and Broad CO lines from the Interacting Supernova Remnant HB 3