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The Peculiar Velocities of Local Type Ia Supernovae and Their Impact on Cosmology

Neill, James D. and Hudson, Michael J. and Conley, Alex (2007) The Peculiar Velocities of Local Type Ia Supernovae and Their Impact on Cosmology. Astrophysical Journal Letters, 661 (2). L123-L126. ISSN 2041-8205.

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We quantify the effect of Type Ia supernova (SN Ia) peculiar velocities on the derivation of cosmological parameters. The published distant and local SNe Ia used for the Supernova Legacy Survey first-year cosmology report form the sample for this study. While previous work has assumed that the local SNe are at rest in the CMB frame (the no-flow assumption), we test this assumption by applying peculiar velocity corrections to the local SNe using three different flow models. The models are based on the IRAS PSCz galaxy redshift survey, have varying β = Ω^(0.6)_m/b, and reproduce the Local Group motion in the CMB frame. These data sets are then fit for w, Ω_m, and Ω_Λ using flatness or ΛCDM and a BAO prior, and the χ^2 statistic is used to examine the effect of the velocity corrections on the quality of the fits. The most favored model is the β = 0.5 model, which produces a fit significantly better than the no-flow assumption, consistent with previous peculiar velocity studies. By comparing the no-flow assumption with the favored models, we derive the largest potential systematic error in w caused by ignoring peculiar velocities, Δw = +0.04. For Ω_Λ the potential error is ΔΩ_Λ = -0.04, and for Ω_m the potential error is ΔΩ_m < +0.01. The favored flow model (β = 0.5) produces the following cosmological parameters: w = -1.08^(+0.09)_(-0.08), Ω_m = 0.27^(+0.02)_(-0.02) assuming a flat cosmology, and Ω_Λ = 0.80^(0.08)_(-0.07) and Ω_m = 0.27^(+0.02)_(-0.02) for a w = -1 (ΛCDM) cosmology.

Item Type:Article
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Neill, James D.0000-0002-0466-1119
Additional Information:© 2007 American Astronomical Society. Received 2007 March 5; accepted 2007 April 12; published 2007 May 11.
Group:Space Astrophysics Laboratory
Subject Keywords:galaxies: distances and redshifts; large-scale structure of universe; supernovae: general
Issue or Number:2
Record Number:CaltechAUTHORS:20100419-103646871
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Official Citation:James D. Neill et al 2007 ApJ 661 L123 doi: 10.1086/518808
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:18017
Deposited By: Jason Perez
Deposited On:19 Apr 2010 18:12
Last Modified:03 Oct 2019 01:36

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