Phenomenology and Dynamical Evolution of Compact Steep Spectrum Sources

ABSTRACT Statistical, analytical and numerical methods have been used to develop a model for phenomenology and dynamical evolution of Compact Steep Spectrum (CSS) sources through the ambient medium of density, e n , within a characteristic time, T . Results show that the empirical relation between spectral turnover, n p , and D implies that 0.34 n p e ~ n , suggesting that the spectral turnover constitutes a characteristic signature of dense gases around CSS sources. However, since the characteristic age of the source is proportional to D , the n p - D relation seems to suggest a decrease in n p as the source ages. This implies that above a certain age range, spectral turnover, n p , may not be observed. The upper limit of this age range corresponds to the order of the minimum age of larger radio sources. Therefore, the effects of orientation and density do not obviate the fact that these sources are in their early stages of evolution; hence, we suggest that CSS sources are young radio sources growing in dense media.