A precise and accurate determination of the cosmic microwave background temperature at z = 0.89
Journal article, 2013

Context. According to the Big Bang theory and as a consequence of adiabatic expansion of the Universe, the temperature of the cosmic microwave background (CMB) increases linearly with redshift. This relation is, however, poorly explored, and detection of any deviation would directly lead to (astro-)physics beyond the standard model. Aims. We aim to measure the temperature of the CMB with an accuracy of a few percent at z = 0.89 toward the molecular absorber in the galaxy lensing the quasar PKS 1830−211. Methods. We adopted a Monte-Carlo Markov chain approach, coupled with predictions from the non-LTE radiative transfer code RADEX, to solve the excitation conditions of a set of various molecular species directly from their spectra. Results. We determine TCMB = 5.08  ±  0.10 K at 68% confidence level. Our measurement is consistent with the value TCMB = 5.14 K predicted by the standard cosmological model with adiabatic expansion of the Universe. This is the most precise determination of TCMB at z > 0 to date.

cosmology: observations / cosmic background radiation / cosmological parameters / quasars: absorption lines / quasars: individual: PKS 1830 / 211


Sebastien Muller

Chalmers, Earth and Space Sciences, Onsala Space Observatory

A. Beelen

University of Paris-Sud

John H Black

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

S.J. Curran

ARC Centre of Excellence for All-sky Astrophysics (CAASTRO)

The University of Sydney

Cathy Horellou

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

Susanne Aalto

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

F. Combes

Centre national de la recherche scientifique (CNRS)

M. Guélin

Institut de RadioAstronomie Millimetrique (IRAM)

Ecole Normale Superieure (ENS)

C. Henkel

King Abdulaziz University

Max Planck Society

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 551 A109 (pp. 1-13) A109

Subject Categories

Astronomy, Astrophysics and Cosmology


Basic sciences


Onsala Space Observatory



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