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

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Abstract
We compare the peculiar velocity field within 65 h-1 Mpc predicted from 2MASS photometry and public redshift data to three independent peculiar velocity surveys based on Type Ia supernovae, surface brightness fluctuations in elliptical galaxies, and Tully-Fisher distances to spiral galaxies. The three peculiar velocity samples are each in good agreement with the predicted velocities and produce consistent results for βK = Ω/bK. Taken together, the best-fit βK = 0.49 ± 0.04. We explore the effects of morphology on the determination of β by splitting the 2MASS sample into E+S0 and S+Irr density fields and find that both samples are equally good tracers of the underlying dark matter distribution, but that early types are more clustered, by a relative factor bE/bS ~ 1.6. The density fluctuations of 2MASS galaxies in 8 h-1 Mpc spheres in the local volume is found to be σ8,K = 0.9. From this result and our value of βK, we find σ8(Ωm/0.3)0.6 = 0.91 ± 0.12. This is in excellent agreement with results from the IRAS redshift surveys, as well as other cosmological probes. Combining the 2MASS and IRAS peculiar velocity results yields σ8(Ωm/0.3)0.6 = 0.85 ± 0.05.
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