PAH and Dust Processing in Supernova Remnants

¹ SOFIA Science Mission Operations/USRA, NASA Ames Research Center, MS 211-3, Moffett Field, CA 94035, USA ;
e-mail: jrho@sofia.usra.edu
² Research & Scientific Support Department, European Space Agency, ESTEC, Keplerlaan 1, 2200 AG Noordwijk, The Netherlands
³ Harvard-Smithsonian Center for Astrophysics, MS 83, 60 Garden Street, Cambridge, MA 02138, USA
⁴ Centre d’Étude Spatiale des Rayonnements, CNRS, 9 Av. du Colonel Roche, BP. 4346, 31028 Toulouse, France
⁵ NASA/Goddard Space Flight Center, Code 662, Greenbelt, MD 20771, USA

Abstract

I present observations of shock-processed PAHs and dust in supernova remnants (SNRs). Supernova shocks are one of the primary sites destroying, fragmenting and altering interstellar PAHs and dust. Studies of PAHs through supernova shocks had been limited because of confusion with PAHs in background emission. Spitzer observations with high sensitivity and resolution allow us to separate PAHs associated with the SNRs and unrelated, Galactic PAHs. In the young SNR N132D, PAH features are detected with a higher PAH ratio of 15–20/7.7 μm than those of other astronomical objects, and we suggest large PAHs have survived behind the shock. We present the spectra of additional 14 SNRs observed with Spitzer IRS and MIPS SED covering the range of 5–90 μm. Bright PAH features from 6.2 to 15–20 μm are detected from many of SNRs which emit molecular hydrogen lines, indicating that both large and small PAHs survive in low velocity shocks. We observe a strong correlation between PAH detection and carbonaceous small grains, while a few SNRs with dominant silicate dust lack PAH features. We characterize PAHs depending on the shock velocity, preshock density and temperature of hot gas, and discuss PAH and dust processing in shocks and implication of PAH and dust cycles in ISM.