NH${}_3$(3,3) and CH${}_3$OH near Supernova Remnants: GBT and VLA Observations

Abstract

We report on Green Bank Telescope 23.87 GHz NH${}_3$(3,3), emission observations in five supernova remnants interacting with molecular clouds (G1.4$-$0.1, IC443, W44, W51C, and G5.7$-$0.0). The observations show a clumpy gas density distribution, and in most cases the narrow line widths of $\sim 3-4$\,km\,s${}^{-1}$ are suggestive of maser emission. Very Large Array observations reveal 36~GHz and/or 44~GHz CH${}_3$OH, maser emission in a majority (72\%) of the NH${}_3$, peak positions towards three of these SNRs. This good positional correlation is in agreement with the high densities required for the excitation of each line. Through these observations we have shown that CH${}_3$OH, and NH${}_3$, maser emission can be used as indicators of high density clumps of gas shocked by supernova remnants, and provide density estimates thereof. Modeling of the optical depth of the NH${}_3$(3,3) emission is compared to that of CH${}_3$OH, constraining the densities of the clumps to a typical density of the order of $10^5$~cm${}^{-3}$ for cospatial masers. Regions of gas with this density are found to exist in the post-shocked gas quite close to the SNR shock front, and may be associated with sites where cosmic rays produce gamma-ray emission via neutral pion decay.

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Cited by in corpus (13)

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• MOLPOP-CEP: An Exact, Fast Code for Multi-Level Systems
• The physical parameters of clumps associated with class I methanol masers
• The Interaction Between the Supernova Remnant W41 and the Filamentary Infrared Dark Cloud G23.33-0.30
• Observations of multiple NH${}_3$ transitions in W33
• The isothermal evolution of a shock-filament interaction
• Discovery of ammonia (9,6) masers in two high-mass star-forming regions
• Modelling cosmic masers in C-type shock waves -- the coexistence of Class I CH3OH and 1720 MHz OH masers
• Molecular Shocks and the Gamma-ray Clouds of the W28 Supernova Remnant
• Discovery of widespread non-metastable ammonia masers in the Milky Way
• Collisional Pumping of OH Masers near Supernova Remnants
• Collisional Pumping of H${}_2$O and CH${}_3$OH Masers in C-Type Shock Waves