2016ApJ...831..192Z

Kes 79 (G33.6+0.1) is an aspherical thermal composite supernova remnant (SNR) observed across the electromagnetic spectrum and showing an unusual highly structured morphology, in addition to harboring a central compact object (CCO). Using the CO J = 1-0, J = 2-1, and J = 3-2 data, we provide the first direct evidence and new morphological evidence to support the physical interaction between the SNR and the molecular cloud in the local standard of rest velocity ∼105 km s^–1. We revisit the 380 ks XMM-Newton observations and perform a dedicated spatially resolved X-ray spectroscopic study with careful background subtraction. The overall X-ray-emitting gas is characterized by an under-ionized (τ_c∼6×10¹¹ cm^–3) cool (kT_c~0.20 keV) plasma with solar abundances, plus an under-ionized (τ_h∼8×10¹⁰ cm^–3) hot (kT_h~0.80 keV) plasma with elevated Ne, Mg, Si, S, and Ar abundances. The X-ray filaments, spatially correlated with the 24 \mum IR filaments, are suggested to be due to the SNR shock interaction with dense gas, while the halo forms from SNR breaking out into a tenuous medium. Kes 79 appears to have a double-hemisphere morphology viewed along the symmetric axis. Projection effect can explain the multiple-shell structures and the thermal composite morphology. The high-velocity, hot (kT_h∼1.4\mbox–1.6 keV) ejecta patch with high metal abundances, together with the non-uniform metal distribution across the SNR, indicate an asymmetric SN explosion of Kes 79. We refine the Sedov age to 4.4-6.7 kyr and the mean shock velocity to 730  km s^–1. Our multi-wavelength study suggests a progenitor mass of ∼15-20 solar masses for the core-collapse explosion that formed Kes 79 and its CCO, PSR J1852+0040.