THE EFFECT OF PECULIAR VELOCITIES ON SUPERNOVA COSMOLOGY
- School of Mathematics and Physics, University of Queensland, QLD 4072 (Australia)
- Department of Physics, Institute for Strings, Cosmology and Astroparticle Physics (ISCAP), Columbia University, New York, NY 10027 (United States)
- Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue Chicago, IL 60637 (United States)
- Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen O (Denmark)
- Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701 (South Africa)
- Center for Particle Astrophysics, Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510 (United States)
- Department of Physics, AlbaNova, Stockholm University, SE-106 91, Stockholm (Sweden)
- Institute of Cosmology and Gravitation, Dennis Sciama Building, Burnaby Road, University of Portsmouth, Portsmouth, PO1 3FX (United Kingdom)
- Physics Department, Rochester Institute of Technology, 85 Lomb Memorial Drive, Rochester, NY 14623-5603 (United States)
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 (United States)
- Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States)
- Astrophysics, Cosmology and Gravity Centre, Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701 (South Africa)
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 {Delta}w {approx} 0.04 (at fixed {Omega}{sub m}), the additional local-motion correction is currently negligible ({Delta}w {approx}< 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 {Delta}w {approx} 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.
- OSTI ID:
- 21612740
- Journal Information:
- Astrophysical Journal, Vol. 741, Issue 1; Other Information: DOI: 10.1088/0004-637X/741/1/67; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
COSMOLOGY AND ASTRONOMY
COSMOLOGY
DIPOLES
EQUATIONS OF STATE
GALAXIES
INDICATORS
LUMINOSITY
MATRICES
RED SHIFT
RELICT RADIATION
SUPERNOVAE
BINARY STARS
ELECTROMAGNETIC RADIATION
EQUATIONS
ERUPTIVE VARIABLE STARS
MICROWAVE RADIATION
MULTIPOLES
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
STARS
VARIABLE STARS