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Standard Rulers, Candles, and Clocks from the Low-Redshift Universe

Alan Heavens, Raul Jimenez, and Licia Verde
Phys. Rev. Lett. 113, 241302 – Published 11 December 2014
Physics logo See Synopsis: Cosmic Ruler Measured More Directly

Abstract

We measure the length of the baryon acoustic oscillation (BAO) feature, and the expansion rate of the recent Universe, from low-redshift data only, almost model independently. We make only the following minimal assumptions: homogeneity and isotropy, a metric theory of gravity, a smooth expansion history, and the existence of standard candles (supernovæ) and a standard BAO ruler. The rest is determined by the data, which are compilations of recent BAO and type IA supernova results. Making only these assumptions, we find for the first time that the standard ruler has a length of 103.9±2.3h1Mpc. The value is a measurement, in contrast to the model-dependent theoretical prediction determined with model parameters set by Planck data (99.3±2.1h1Mpc). The latter assumes the cold dark matter model with a cosmological constant, and that the ruler is the sound horizon at radiation drag. Adding passive galaxies as standard clocks or a local Hubble constant measurement allows the absolute BAO scale to be determined (142.8±3.7Mpc), and in the former case the additional information makes the BAO length determination more precise (101.9±1.9h1Mpc). The inverse curvature radius of the Universe is weakly constrained and consistent with zero, independently of the gravity model, provided it is metric. We find the effective number of relativistic species to be Neff=3.53±0.32, independent of late-time dark energy or gravity physics.

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  • Received 22 September 2014

DOI:https://doi.org/10.1103/PhysRevLett.113.241302

© 2014 American Physical Society

Synopsis

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Cosmic Ruler Measured More Directly

Published 11 December 2014

A measure of how galaxies are spatially distributed can be determined in a new, more robust way.

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Authors & Affiliations

Alan Heavens1,*, Raul Jimenez2,3,†, and Licia Verde2,4,‡

  • 1Imperial Centre for Inference and Cosmology, Imperial College, Blackett Laboratory, Prince Consort Road, London SW7 2AZ, United Kingdom
  • 2ICREA & ICC, University of Barcelona, Martí i Franquès 1, E-08028 Barcelona, Spain
  • 3Institute for Applied Computational Science, Harvard University, Cambridge, Massachusetts 02138, USA
  • 4Institute of Theoretical Astrophysics, University of Oslo, 0315 Oslo, Norway

  • *a.heavens@imperial.ac.uk
  • raul.jimenez@icc.ub.edu
  • liciaverde@icc.ub.edu

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Issue

Vol. 113, Iss. 24 — 12 December 2014

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