A Tolman Surface Brightness Test for Universal Expansion and the Evolution of Elliptical Galaxies in Distant Clusters

We use the intercept of the elliptical galaxy radius--surface brightness (SB)relation at a fixed metric radius as the standard condition for the Tolman SBtest of the universal expansion. We use surface photometry in the optical andnear-IR of elliptical galaxies in Abell~2390 ($z=0.23$) and Abell~851($z=0.41$), and compare them to the Coma cluster at $z\approx 0$. Thephotometric data for each cluster are well-described by the Kormendy relation$r_e \propto \Sigma_e^{A}$, where $A=-0.9$ in the optical and $A=-1.0$ in thenear-IR. The scatter about this near-IR relation is only $0.076$ in $\log r_e$at the highest redshift, which is much smaller than at low redshifts,suggesting a remarkable homogeneity of the cluster elliptical population at$z=0.41$. We use the intercept of these fixed-slope correlations at $R_e =1$~kpc (assuming $H_0=75$~km~s$^{-1}$~Mpc$^{-1}$, $\Omega_0=0.2$, and$\Lambda_0=0$, where the results are only weakly dependent on the cosmology) toconstruct the Tolman SB test for these three clusters. The data are fullyconsistent with universal expansion if we assume simple models of passiveevolution for elliptical galaxies, but are inconsistent with a non-expandinggeometry (the tired light cosmology) at the $5 \, \sigma$ confidence level at$z=0.41$. These results suggest luminosity evolution in the restframe $K$-bandof $0.36 \pm 0.14$~mag from $z = 0.41$ to the present, and are consistent withthe ellipticals having formed at high redshift. The SB intercept in ellipticalgalaxy correlations is thus a powerful tool for investigating models of theirevolution for significant lookback times.