The low radio frequency properties of the SNR Kes 79

GABRIELA CASTELLETTI, ELSA GIACANI, SERGIO PARON, GLORIA DUBNER

Isla Margarita - Venezuela

Congreso; XII Reunión Regional Latinoamericana de Astronomía; 2007

Observations of the supernova remnants (SNRs) at meter and longer wavelengthsare powerful tools to differentiate physical processes taking place either in the SNRs (e.g. shock acceleration) or in the interstellar medium intervening along the line ofsight towards them (e.g. thermal absorption).Kes 79 (G33.6+0.1) is a Galactic SNR rich in spatial structures in both, radio and Xray bands, that make it ideal for addressing questions of SNR physics. Its radio morphologyat 1.5 GHz is dominated by a system of two concentric incomplete shells with diametersabout 80 and 120. Chandra observations of Kes 79 reveal many filaments, multiple partialshells, a loop, and a protrusion. The X-ray point source, CXOUJ 185238.6+004020,located close to the geometric center of the remnant was proposed to be the compactstellar remnant formed in the supernova event, although no evidence for a surroundingpulsar wind nebula was found in the X-rays. It has also been suggested that Kes 79 isinteracting with a molecular cloud that appears to be partially surrounding its east andsoutheast borders. In this work we present new high quality images of Kes 79 obtained at low radio frequencies. The observations at 74 and 324 MHz were carried out using multipleconfigurations of the Very Large Array (VLA) of the NRAO. We use these data and existing VLA observations at 1.5 GHz to perform an accurate study of the spectral index behaviour over the remnant and its relationship with the properties in the X-ray band of Kes 79. In addition, using HI and CO data from public databases we investigate the influence of the surrounding gas on the morphology of Kes 79.