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The local extragalactic velocity field, the local mean mass density, and biased galaxy formation

Brown, M. E. and Peebles, P. J. E. (1987) The local extragalactic velocity field, the local mean mass density, and biased galaxy formation. Astrophysical Journal, 317 (2). pp. 588-592. ISSN 0004-637X. http://resolver.caltech.edu/CaltechAUTHORS:20121002-114716076

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Abstract

The biased galaxy formation picture accounts for the low apparent mass density derived from clustering dynamics by the assumption that the mass per galaxy is unusually low in the regions of high density where clustering has been studied. It would follow that the mass per galaxy is unusually high where the mass density is low, and, by continuity, that the mass per galaxy is close to the global mean in regions where the ambient mass density, p_t, is close to the global mean, P_b. That is, we would expect that the best chance for an unbiased estimate of the mean mass per galaxy, and hence of P_b, would be from the dynamics of regions with p_t ≈ P_b. The local density at redshifts 200 ≾ cz ≾ 400 km s^(-l) must be close to P_b because, as Sandage has emphasized, the local Hubble flow is so little perturbed. In this paper we derive a relationship between the local mass density and the perturbation of the local Hubble flow. The local mass density is estimated by the method used in the Virgocentric flow. We use the infrared Tully-Fisher distances of Aaronson et al. to find limits on the gravitational perturbation to the local Hubble flow, and we use bright galaxy counts, N, to estimate the local galaxy concentration. The statistics on the latter are weak because N is small. We can conclude, however, that if mass were proportional to N, with no fluctuations, and the local mass per galaxy were a fair sample, then the density parameter (Ω = P_b/Einstein-de Sitter density) would be Ω ≈ 0.1, consistent with the other dynamical estimates and inconsistent with the above naive interpretation of biasing.


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http://dx.doi.org/10.1086/165304DOIUNSPECIFIED
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Additional Information:© 1987 American Astronomical Society. Provided by the NASA Astrophysics Data System. Received 1986 September 18; accepted 1986 November 26. We thank Dick Bond, John Huchra, Bob Schommer, and Scott Tremaine for stimulating comments. This research was supported in part by the National Science Foundation.
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Subject Keywords:cosmology; galaxies: clustering; galaxies: formation; galaxies: redshifts
Record Number:CaltechAUTHORS:20121002-114716076
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20121002-114716076
Official Citation:The local extragalactic velocity field, the local mean mass density, and biased galaxy formation Brown, M. E.; Peebles, P. J. E. Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 317, June 15, 1987, p. 588-592.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:34627
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:02 Oct 2012 20:38
Last Modified:27 Dec 2012 02:47

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