Comparison of the SFI peculiar velocities with the IRAS 1.2-Jy gravity field |
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| Authors: | Luiz N da Costa Adi Nusser Wolfram Freudling Riccardo Giovanelli Martha P Haynes John J Salzer & Gary Wegner |
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| Institution: | European Southern Observatory, Karl-Schwarzschild Strasse 2, D-85748 Garching bei Mu¨nchen, Germany,;Max-Planck-Institut fu¨r Astrophysik, Karl-Schwarzschild-Strasse 1, D-85749 Garching bei Mu¨nchen, Germany,;Space Telescope–European Coordinating Facility, European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei Mu¨nchen, Germany,;Center for Radiophysics and Space Research and National Astronomy and Ionosphere Center, Cornell University, Ithaca, NY 14853, USA,;Department of Astronomy, Wesleyan University, Middletown, CT 06457, USA,;Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755, USA,;Departamento de Astronomia CNPq/Observatório Nacional, rua General JoséCristino 77, Rio de Janeiro, R.J. 20921 Brazil |
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| Abstract: | We present a comparison between the peculiar velocity fields measured from a recently completed l -band Tully–Fisher survey of field spirals (SFI) and that derived from the IRAS 1.2-Jy redshift survey galaxy distribution. The analysis is based on the expansion of these data in redshift space using smooth orthonormal functions, and is performed using low- and high-resolution expansions, with an effective smoothing scale which increases almost linearly with redshift. The effective smoothing scales at 3000 km s?1 are 1500 and 1000 km s?1 for the low- and high-resolution filters. The agreement between the high- and low-resolution SFI velocity maps is excellent. The general features in the filtered SFI and IRAS velocity fields agree remarkably well within 6000 km s?1. This good agreement between the fields allows us to determine the parameter β = Ω0.6 / b , where Ω is the cosmological density parameter, and b is the linear biasing factor. From a likelihood analysis on the SFI and IRAS modes we find that β = 0.6 ± 0.1, independently of the resolution of the modal expansion. For this value of β, the residual fields for the two filters show no systematic variations within 6000 km s?1. Most remarkable is the lack of any coherent, redshift-dependent dipole flow in the residual field. |
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| Keywords: | cosmology: observations dark matter large-scale structure of Universe |
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