Cosmological Parameters from the Comparison of the 2MASS Gravity Field with Peculiar Velocity Surveys

We compare the peculiar velocity field within 65 $h^{-1}$ Mpc predicted from2MASS photometry and public redshift data to three independent peculiarvelocity surveys based on type Ia supernovae, surface brightness fluctuationsin ellipticals, and Tully-Fisher distances to spirals. The three peculiarvelocity samples are each in good agreement with the predicted velocities andproduce consistent results for $\beta_{K}=\Omega\sbr{m}^{0.6}/b_{K}$. Takentogether the best fit $\beta_{K} = 0.49 \pm 0.04$. We explore the effects ofmorphology on the determination of $\beta$ by splitting the 2MASS sample intoE+S0 and S+Irr density fields and find both samples are equally good tracers ofthe underlying dark matter distribution, but that early-types are moreclustered by a relative factor $b\sbr{E}/b\sbr{S} \sim 1.6$. The densityfluctuations of 2MASS galaxies in $8 h^{-1}$ Mpc spheres in the local volume isfound to be $\sigma\sbr{8,K} = 0.9$. From this result and our value of$\beta_{K}$, we find $\sigma_8 (\Omega\sbr{m}/0.3)^{0.6} = 0.91\pm0.12$. Thisis in excellent agreement with results from the IRAS redshift surveys, as wellas other cosmological probes. Combining the 2MASS and IRAS peculiar velocityresults yields $\sigma_8 (\Omega\sbr{m}^/0.3)^{0.6} = 0.85\pm0.05$.Comment: 11 pages, ApJ accepte