Low radio frequency constraints to the spectrum of galactic supernova remnants

CASTELLETTI G.; SUPAN L.; LANE W.; KASSIM N. E.; DUBNER G.

Córdoba

Congreso; 57a Reunión Anual de la Asociación Argentina de Astronomía; 2014

Observatorio Astronómico de Córdoba

Radio continuum spectra made accurate by extension to low  frequency measurements provide a sensitive and often unique means of distinguishing between intrinsic and extrinsic physical processes that shape supernova remnants (SNRs). Low radio frequencies are also the key to resolve the uncertainty in the electron power spectrum at low energies, which otherwise must be extrapolated based on higher frequency data. The observations in this extreme of the electromagnetic spectrum are also essential to constrain theories that explain  high-energy particle production in SNRs, thus helping to understand the nature of the gamma-ray emission associated with SNRs. We used recently reprocessed data from the Very Large Array (VLA)  Low-frequency Sky Survey Redux (VLSSr) to calculate the integrated flux  density at 74 MHz for 22 Galactic SNRs, with a resolution of approximately 80´´ and an rms  sensitivity of about 0.1 Jy/beam. From a careful combination with published flux density values at higher radio frequencies we were able to construct for the first time accurate radio continuum spectra of the remnants and to constrain the physical properties of ionized gas in the interstellar medium.