Are Luminosities of Radio Galaxies Affected by Dark Energy?

Dark energy is an intrinsic property of the space-time. At astronomical distances, it is the energy strongly believed to be driving the observed accelerated expansion of the space-time or the universe as whole. Analytical and statistical methods have been used in this work to find possible effect(s) (if any) of this observed space-time expansion on radio galaxies. This is done by carrying out simple linear regression analyses on some larger (or the more extended radio galaxies), and on some smaller (or the more compact radio galaxies). The two plots show good correlations. The result of the more compact sources shows a direct power-law function, while that of the more extended sources indicates an inverse power-law function. We noted that this disagreement must have originated from the ambient environments in which the two subclasses of objects are domiciled. Since they have been shown to be situated in different ambient media, their observable physical processes should not be expected to be exactly the same. Therefore, since the more compact radio galaxies are generally sub-galactic in dimensions, they are affected more by their denser ambient gases and interstellar gravitational pull. In contrast to this, the components of larger radio galaxies are located in the intergalactic media where there is insufficient gravitational pull and little amounts of dust particles. Hence, space expansion should naturally be expected to affect the luminosities of the larger radio galaxies. This is shown in the obtained relation, L~ -R-0.9 ; where R is source velocity of recession, and L is source luminosity. The result simply shows that the observed universal space-time expansion may affect the luminosities of the more extended radio galaxies. Moreover, comparing the two results obtained (L~ -R-0.9 for the larger radio galaxies, and L~ -R-0.096 for the more compact radio galaxies), we find that if we assume little or no effect of the observed space-time expansion on CSS galaxies, the effect is much more appreciable on the larger radio galaxies. Using the two results, the effect is estimated to be about 10 times more on the luminosities of the larger sources than on those of the smaller sources.