Looking into Dark Energy Effect on the Extragalactic Radio Quasar Luminosity Evolution

In this work, we use both analytical methods and statistical methods to find effect of dark energy on the extragalactic radio (EGR) quasar luminosity evolution. We carry out linear regression analysis of observed source linear sizes (D) of the more extended radio quasars against their corresponding observed redshifts (z) sample. Also, we carry out similar analysis on the observed linear sizes of compact steep spectrum (CSS) quasars against their corresponding observed redshifts. Results of the regressions indicate that if we take D to be distance between any two positions in the environment in which the source is domiciled, then cosmic evolution relates inversely with the distance between the two positions in question – it is given by where and for the more extended EGR quasars and CSS quasars respectively. Since “a higher redshift implies an earlier epoch”, and redshift has a direct dependence on expansion velocity between any two points in space, the results of the analyses simply suggest that at earlier epoch, the expansion rate of the universe was higher. Our results also indicate that the effect of cosmic evolution in the extended EGR quasars is more than the effect in the CSS quasars . Since the linear sizes of the more extended EGR quasars are projected into the intergalactic medium (IGM), while the linear sizes of the CSS quasars are domiciled within their individual host galaxies (i.e. the interstellar medium [ISM]), the result can be interpreted to mean that cosmic evolution shows greater effect in the IGM (i.e. more rarefied medium) than in the ISM (i.e. less rarefied medium). Hence, from the results of the analyses, we may state that if dark energy is defined as the intrinsic tendency of vacuum (or free space) to increase in volume, then the inconsistency in and is simply a manifestation of dark energy. Therefore, we may state that dark energy constitutes a driving parameter behind cosmic evolution. Moreover, semi-empirically, we find that as ; where are powers of the central engines of CSS quasars and the more extended quasars respectively. are respectively luminosity of CSS quasars and that of the more extended quasars. It states that the power of the central engine of the CSS quasar is much greater than that of the more extended quasar when matched at the same epoch. This is in harmony with luminosities since they are expected to show direct power-law function with the source central engine. In conclusion, our results suggest that since the components of the more EGR quasars are in the IGM and , dark energy may be responsible for the diminution effect on their luminosities.