2001ApJ...561L..41R

Using a redshift survey of 1779 galaxies and photometry from the Two Micron All Sky Survey covering 200 deg², we calculate independent mass and light profiles for the infall region of the Coma Cluster of galaxies. The redshift survey is complete to K_s=12.2 (622 galaxies), 1.2 mag fainter than M^*_Ks at the distance of Coma. We confirm the mass profile obtained by Geller, Diaferio, and Kurtz. The enclosed mass-to-light ratio measured in the K_s band is approximately constant to a radius of 10 h^–1 Mpc, where M/L_Ks=75±23 h M_☉/L_☉, in agreement with weak-lensing results on similar scales. Within 2.5 h^–1 Mpc, X-ray estimates yield similar mass-to-light ratios (67±32 h). The constant enclosed mass-to-light ratio with radius suggests that the K-band light from bright galaxies in clusters traces the total mass on scales ≲10 h^–1 Mpc. Uncertainties in the mass profile imply that the mass-to-light ratio inside r₂₀₀ may be as much as a factor of 2.5 larger than that outside r₂₀₀. These data demonstrate that the K-band light is not positively biased with respect to the mass; we cannot rule out antibias. These results imply that Ω_m=0.17±0.05. Estimates of possible variations in M/L_Ks with radius suggest that the density parameter is no smaller than Ω_m~0.08.