Journal Article

On measuring the absolute scale of baryon acoustic oscillations

Will Sutherland

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 426, issue 2, pages 1280-1290
Published in print October 2012 | ISSN: 0035-8711
Published online October 2012 | e-ISSN: 1365-2966 | DOI:
On measuring the absolute scale of baryon acoustic oscillations

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The baryon acoustic oscillation (BAO) feature in the distribution of galaxies provides a fundamental standard ruler which is widely used to constrain cosmological parameters. In most analyses, the comoving length of the ruler is inferred from a combination of cosmic microwave background (CMB) observations and theory. However, this inferred length may be biased by various non-standard effects in early universe physics; this can lead to biased inferences of cosmological parameters such as H0, Ωm and w, so it would be valuable to measure the absolute BAO length by combining a galaxy redshift survey and a suitable direct low-z distance measurement. One obstacle is that low-redshift BAO surveys mainly constrain the ratio rS/DV(z), where DV is a dilation scale which is not directly observable by standard candles. Here, we find a new approximation which connects DV to the standard luminosity distance DL at a somewhat higher redshift; this is shown to be very accurate (relative error <0.2 per cent) for all Wilkinson Microwave Anisotropy Probe compatible Friedmann models at z < 0.4, with very weak dependence on cosmological parameters H0, Ωm, Ωk, w. This provides a route to measure the absolute BAO length using only observations at z ≲ 0.3, including Type Ia supernovae, and potentially future H0-free physical distance indicators such as gravitational lenses or gravitational wave standard sirens. This would provide a zero-parameter check of the standard cosmology at 103z ≲ 105, and can constrain the number of relativistic species Neff with fewer degeneracies than the CMB.

Keywords: cosmic background radiation; distance scale; large-scale structure of Universe

Journal Article.  9287 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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