Omega and Biasing from Optical Galaxies vs. POTENT Mass

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Session 119 -- Galaxies and Clusters of Galaxies, X-Ray Observationsd
Oral presentation, Thursday, 12, 1995, 2:00pm - 3:30pm

[119.05] Omega and Biasing from Optical Galaxies vs. POTENT Mass

M. J. Hudson (Durham), A. Dekel (Hebrew University), S. Courteau (Kitt Peak), S. M. Faber (UCO/Lick), J. A. Willick (Carnegie)

The mass density field in the local universe, recovered by the POTENT method from peculiar velocities of $\sim$3000 galaxies, is compared with the density field of optically-selected galaxies, both smoothed with a Gaussian filter of radius 12 $h^{-1}$ Mpc. Under the assumptions of gravitational instability and a linear biasing parameter $b_{\rm O}$ between optical galaxies and mass, we obtain from a regression of POTENT density on optical density, corrected for systematic biases in the velocity data and POTENT method, $\beta_{\rm O} \equiv \Omega^{0.6}/b_{\rm O} = 0.74 \pm 0.13$. The error quoted is just the $1\sigma$ formal error estimated from the observed scatter in the density--density scatterplot; it does not include the uncertainty due to cosmic scatter in the mean density or in the biasing relation. We do not attempt a formal analysis of the goodness of fit, but the scatter about the fit is consistent with our estimates of the uncertainties.

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