On Compact Steep Spectrum Radio Quasars/Galaxies and Youth Scenario

Abstract

Statistical methods of analyses have been used to find some difference in some parametric relationships in the two subclasses of compact steep spectrum (CSS) sources. These sub-classes include CSS quasars and CSS galaxies. This is done by carrying out linear regression analyses on the observed source linear sizes  against their respective observed redshifts  – the analyses are carried out individually for the quasars and the galaxies. Moreover, similar regression analyses are carried out on the observed source linear sizes against their respective observed luminosities . For the CSS quasars, result indicates that observed linear size shows an inverse relationship with observed redshift; while for the CSS galaxies, the converse is the case. On the linear size/luminosity plane, similar trends respectively for the CSS quasars and CSS galaxies are obtained. That is, for the quasars result shows an inverse relationship between linear size and luminosity; while for the galaxies, the relationship between the two observable parameters is a direct one. The  data show that CSS quasars evolve both in size and radiated power output with time; while for the galaxies the opposite is the case.  These results suggestively indicate that at earlier epoch, CSS galaxies appear more extended in sizes and radiated power than the CSS quasars. Therefore, in conclusion, we may state that in addition to supporting Youth Scenario (i.e. young sources evolving in dense ambient media), dynamical evolution of CSS galaxies is different from that of quasars – while CSS quasars evolve dynamically and progressively as well, CSS galaxies suffer retrogressive dynamical evolution.