Quantifying the accuracy of the AlcockPaczyński scaling of baryon acoustic oscillation measurements
Abstract
We investigate—in a generic setting—the regime of applicability of the AlcockPaczyński (AP) scaling conventionally applied to test different cosmological models, given a fiducial measurement of the baryon acoustic oscillation (BAO) characteristic scale in the galaxy 2point correlation function. We quantify the error in conventional AP scaling methods, for which our ignorance about the true cosmology is parameterised in terms of two constant AP scaling parameters. We propose a new, and as it turns out, improved version of the constant AP scaling, also consisting of two scaling parameters.
The two constant AP scaling methods are almost indistinguishable when the fiducial model used in data reduction and the "true" underlying cosmology are not differing substantially in terms of metric gradients, but are otherwise expected to differ. Our new methods can be applied to existing analyses through a reinterpretation of the results of the conventional AP scaling. This reinterpretation might be important in model universes where curvature gradients above the scale of galaxies are significant.
We test our theoretical findings on ΛCDM mock catalogues. The conventional constant AP scaling methods are surprisingly successful for pairs of largescale metrics, but eventually break down when toy models allowing for large metric gradients are tested. The new constant AP scaling methods proposed in this paper are efficient for all test models examined. We find systematic errors of ~1% in the recovery of the BAO scale when the true model is distant from the fiducial, which cannot be attributed to any constant AP approximation. The level of systematic uncertainty is robust to the exact fitting method employed. This indicates that caution must be taken with the error budget when extrapolating the BAO acoustic scale measurements obtained in the standard literature.
 Publication:

Journal of Cosmology and Astroparticle Physics
 Pub Date:
 January 2020
 DOI:
 10.1088/14757516/2020/01/038
 arXiv:
 arXiv:1908.11508
 Bibcode:
 2020JCAP...01..038H
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics;
 General Relativity and Quantum Cosmology
 EPrint:
 42 pages, 8 figures, 2 tables