Background photon temperature T¯: A new cosmological Parameter?

Jaiyul Yoo, Ermis Mitsou, Yves Dirian, and Ruth Durrer
Phys. Rev. D 100, 063510 – Published 11 September 2019

Abstract

The background photon temperature T¯ is one of the fundamental cosmological parameters, and it is often set equal to the precise measurement Tobs of the comic microwave background (CMB) temperature by the COBE Far Infrared Absolute Spectrometer (FIRAS). However, even in future CMB experiments, T¯ will remain unknown due to the unknown monopole contribution Θ0 at our position to the observed (angle-averaged) temperature Tobs. Using the Fisher formalism, we find that the standard analysis with T¯Tobs underestimates the error bars on cosmological parameters by 1%2% of the present errors, and the best-fit parameters obtained in the analysis are biased by 1% of their standard deviation. These systematic errors are negligible for the Planck data analysis, providing a justification to the standard practice. However, with T¯Tobs, these systematic errors will always be present and irreducible, and future cosmological surveys might misinterpret the measurements.

  • Figure
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  • Received 24 May 2019
  • Revised 31 July 2019

DOI:https://doi.org/10.1103/PhysRevD.100.063510

© 2019 American Physical Society

Physics Subject Headings (PhySH)

Gravitation, Cosmology & Astrophysics

Authors & Affiliations

Jaiyul Yoo1,2,*, Ermis Mitsou1, Yves Dirian1, and Ruth Durrer3

  • 1Center for Theoretical Astrophysics and Cosmology, Institute for Computational Science, University of Zürich, Winterthurerstrasse 190, Zürich CH-8057, Switzerland
  • 2Physics Institute, University of Zürich, Winterthurerstrasse 190, Zürich CH-8057, Switzerland
  • 3Département de Physique Théorique & Center for Astroparticle Physics, Université de Genève Quai E. Ansermet 24, Genève 4 CH-1211, Switzerland

  • *jyoo@physik.uzh.ch

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Issue

Vol. 100, Iss. 6 — 15 September 2019

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