The effect of peculiar velocities on supernova cosmology

Davis, Tamara M., Hui, Lam, Frieman, Joshua A., Haugbolle, Troels, Kessler, Richard, Sinclair, Benjamin, Sollerman, Jesper, Bassett, Bruce, Marriner, John, Mortsell, Edvard, Nichol, Robert C., Richmond, Michael W., Sako, Masao, Schneider, Donald P. and Smith, Mathew (2011) The effect of peculiar velocities on supernova cosmology. Astrophysical Journal, 741 1: 1-15. doi:10.1088/0004-637X/741/1/67

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Author Davis, Tamara M.
Hui, Lam
Frieman, Joshua A.
Haugbolle, Troels
Kessler, Richard
Sinclair, Benjamin
Sollerman, Jesper
Bassett, Bruce
Marriner, John
Mortsell, Edvard
Nichol, Robert C.
Richmond, Michael W.
Sako, Masao
Schneider, Donald P.
Smith, Mathew
Title The effect of peculiar velocities on supernova cosmology
Journal name Astrophysical Journal   Check publisher's open access policy
ISSN 0004-637X
Publication date 2011-11-01
Sub-type Article (original research)
DOI 10.1088/0004-637X/741/1/67
Open Access Status File (Publisher version)
Volume 741
Issue 1
Start page 1
End page 15
Total pages 15
Place of publication Philadelphia, PA, United States
Publisher Institute of Physics Publishing
Language eng
Formatted abstract
We analyze the effect that peculiar velocities have on the cosmological inferences we make using luminosity distance indicators, such as Type Ia supernovae. In particular we study the corrections required to account for (1) our own motion, (2) correlations in galaxy motions, and (3) a possible local under- or overdensity. For all of these effects we present a case study showing the impact on the cosmology derived by the Sloan Digital Sky Survey-II Supernova Survey (SDSS-II SN Survey). Correcting supernova (SN) redshifts for the cosmic microwave background (CMB) dipole slightly overcorrects nearby SNe that share some of our local motion. We show that while neglecting the CMB dipole would cause a shift in the derived equation of state of Δw ~ 0.04 (at fixed Ω m ), the additional local-motion correction is currently negligible (Δw lsim 0.01). We then demonstrate a covariance-matrix approach to statistically account for correlated peculiar velocities. This down-weights nearby SNe and effectively acts as a graduated version of the usual sharp low-redshift cut. Neglecting coherent velocities in the current sample causes a systematic shift of Δw ~ 0.02. This will therefore have to be considered carefully when future surveys aim for percent-level accuracy and we recommend our statistical approach to down-weighting peculiar velocities as a more robust option than a sharp low-redshift cut.
Keyword Cosmology: observations
Supernovae: general
Digital Sky Survey
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Issue 1 (2011 November 1); Received 2010 October 16, accepted for publication 2011 August 7; Published 2011 October 14 Article #67.

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Mathematics and Physics
Official 2012 Collection
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