Discovery of molecular and atomic clouds associated with the gamma-ray supernova remnant Kesteven 79

Abstract

We carried out ${}^{12}$CO($J$ = 1-0) observations of the Galactic gamma-ray supernova remnant (SNR) Kesteven 79 using the Nobeyama Radio Observatory 45 m radio telescope, which has an angular resolution of $\sim 20$ arcsec. We identified molecular and atomic gas interacting with Kesteven 79 whose radial velocity is $\sim 80$ km s${}^{-1}$. The interacting molecular and atomic gases show good spatial correspondence with the X-ray and radio shells, which have an expanding motion with an expanding velocity of $\sim 4$ km s${}^{-1}$. The molecular gas associated with the radio and X-ray peaks also exhibits a high-intensity ratio of CO 3-2/1-0 $>$ 0.8, suggesting a kinematic temperature of $\sim 24$ K, owing to heating by the supernova shock. We determined the kinematic distance to the SNR to be $\sim 5.5$ kpc and the radius of the SNR to be $\sim 8$ pc. The average interstellar proton density inside of the SNR is $\sim 360$ cm${}^{-3}$, of which atomic protons comprise only $\sim 10$ $\%$. Assuming a hadronic origin for the gamma-ray emission, the total cosmic-ray proton energy above 1 GeV is estimated to be $\sim 5\times 10^{48}$ erg.

12 pages, 6 figures, 2 tables, accepted for publication in The Astrophysical Journal (ApJ)