Redshift evolution of angular diameters and surface brightness: how rigid are galactic measuring rods?

Abstract

The effect of a cosmic time variation of Newton’s constant on galactic angular diameters, linear size, apparent magnitude, and surface brightness is investigated. The redshift scaling of the gravitational constant is proportional to the Hubble parameter, derived from the constancy of a moderate dimensionless ratio of fundamental constants, and manifested in galactic linear-size evolution. The latter is demonstrated by fitting the angular size–redshift relation to spectroscopically and photometrically selected samples of high-redshift rotators. The intrinsic luminosity evolution of the rotators and their magnitude–redshift and surface brightness–redshift relations are studied. The galactic luminosity scales with a power of the Hubble parameter, and the scaling exponent is inferred from a moderate dimensionless ratio involving the gravitational constant, the Galactic luminosity, and the velocity of the Galaxy in the microwave background. The fits are performed with a cosmic expansion factor derived from paleoplanetary surface temperatures. This expansion factor is tested by comparing the corresponding redshift evolution of the angular-size distance to the distance estimates of two samples of galaxy clusters.