|
Abstract:
|
The models of radio synchrotron emission of supernova remnants (SNRs)
imply uniform density ahead of shock wave, so the evolution of luminosity is usu-
ally studied in such an environment, most often through the surface-brightness-to-
diameter dependence, the Σ–D relation. This field aims to better understand the
SNR evolution, the emission models, but also the methods for determining their
distance. It is not an easy task because of a very large scatter in the Σ–D Milky
Way sample.
The dissertation puts a different perspective at the Σ–D relation (usually treated
as power-law function), assuming that non-uniform environment around the stars
considerably affects its shape and slope, that may vary during the SNR expansion.
It makes the ambient density structure an important factor whose impact must
be investigated. The numerical code for hydrodynamic (HD) simulations and the
emission model were developed. The 3D HD simulations were performed in different
non-uniform environments, including low-density bubbles and a variety of clumpy
models. Based on the simulation results, a semi-analytical 3D spherically-symmetric
model of HD and Σ–D evolution of SNRs in clumpy medium was developed, which
is used to generate large Σ–D samples.
The results show that after entering the clumpy medium the SNR brightness
enhances, but afterward the Σ–D slope steepens, shortening the brightness evolu-
tion lifetime. Despite the evident increase in slope in clumpy medium, the Galactic
sample average slope flattens at ≈ 13–50 pc. After analyzing the generated SNR
samples in clumpy medium it is concluded that the significant flattening and scatter
in Galactic sample originates in sporadic emission jumps of individual SNRs in a
limited diameter interval. The additional analyses of selection effects are needed to
investigate these issues. |