PAH and Dust Processing in Supernova Remnants

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 alteringinterstellar PAHs and dust. Studies of PAHs through supernova shocks had been limitedbecause of confusion with PAHs in background emission. Spitzerobservations with high sensitivity and resolution allow us to separate PAHsassociated with the SNRs and unrelated, Galactic PAHs. In the young SNR N132D, PAHfeatures are detected with a higher PAH ratio of 15–20/7.7 μm than thoseof other astronomical objects, and we suggest large PAHs have survived behind the shock.We present the spectra of additional 14 SNRs observed with Spitzer IRSand MIPS SED covering the range of 5–90 μm. Bright PAH features from 6.2to 15–20 μm are detected from many of SNRs which emit molecular hydrogenlines, indicating that both large and small PAHs survive in low velocity shocks. Weobserve a strong correlation between PAH detection and carbonaceous small grains, while afew SNRs with dominant silicate dust lack PAH features. We characterize PAHs depending onthe shock velocity, preshock density and temperature of hot gas, and discuss PAH and dustprocessing in shocks and implication of PAH and dust cycles in ISM.