Chandra View of Kesteven 79: A Nearly Isothermal Supernova Remnant with Rich Spatial Structure

A 30 ks Chandra ACIS-I observation of Kes 79 reveals rich spatial structures, including many filaments, three partial shells, a loop, and a "protrusion." Most of them have corresponding radio features. Regardless of the different results from two nonequilibrium ionization (NEI) codes, temperatures of different parts of the remnant are all around 0.7 keV, which is surprisingly constant for a remnant with such rich structure. If thermal conduction is responsible for smoothing the temperature gradient, a lower limit on the thermal conductivity of ~1/10 of the Spitzer value can be derived. Thus, thermal conduction may play an important role in the evolution of at least some supernova remnants (SNRs). No spectral signature of the ejecta is found, which suggests that the ejecta material has been well mixed with the ambient medium. From the morphology and the spectral properties, we suggest that the bright inner shell is a wind-driven shell (WDS) overtaken by the blast wave (the outer shell) and estimate the age of the remnant to be ~6 kyr for the assumed dynamics. Projection is also required to explain the complicated morphology of Kes 79.