The Environment of Tycho: Possible Interaction with the Molecular Cloud

The Tycho supernova remnant (SNR), as one of the few historical SNRs, hasbeen widely studied in various wavebands. Observations show evidence that Tychois expanding in a medium with density gradient and possibly interacting withdense ambient medium toward the northeast direction. From the FCRAO CO surveyof the outer Galaxy, we have identified a patch of molecular clouds in thisarea and have conducted a follow-up observation with Nobeyama 45m radiotelescope. The high-resolution (16\arcsec) Nobeyama data shows that a largemolecular cloud surrounds the SNR along the northeastern boundary. We suggestthat the Tycho SNR and the molecular cloud are located in the Perseus arm andthat the dense medium interacting with the SNR is possibly the molecular cloud.We also discuss the possible connection between the molecular cloud and theBalmer-dominated optical filaments, and suggest that the preshock gas may beaccelerated within the cosmic ray and/or fast neutral precursor.Comment: 10 pages, 3 figures, ApJL accepte