Constraints on the [Omega_Matter-Omega_Lambda]-plane from Elliptical Galaxy Counts ?

Abstract

Here we present a pilot study into whether elliptical galaxy counts alone, can place a useful constraint on the Omega_M - Omega_Lambda-plane. The elliptical galaxy counts are drawn from three surveys: The Millennium Galaxy Catalogue (16 > B_KPNO > 20), the B-band Parallel Survey (20 > B_AB >24) and the Hubble Deep Fields (23 > B_AB > 28). The elliptical luminosity function used in the modeling was derived from a combination of the Millennium Galaxy Catalogue, the two-degree field galaxy redshift survey and the Sloan Digital Sky Survey (M_*=-19.90, phi_*=0.0019/Mpc^3 and alpha =-0.75 for H_o=75km/s/Mpc). We adopt a benchmark model and tweak the various input parameters by their uncertainties to determine the impact upon the counts. We find that IF the faint-end slope of the elliptical galaxy luminosity function is known to better than 0.1$, then over the magnitude range 16 < B < 23 the counts depend most critically upon the cosmology, and can be used to place a weak constraint on the [Omega_Matter-Omega_Lambda]-plane.