Robust Constraint on a Drifting Proton-to-Electron Mass Ratio at z=0.89 from Methanol Observation at Three Radio Telescopes
Journal article, 2013

A limit on a possible cosmological variation of the proton-to-electron mass ratio μ is derived from methanol (CH3OH) absorption lines in the benchmark PKS1830–211 lensing galaxy at redshift z=0.89 observed with the Effelsberg 100-m radio telescope, the Institute de Radio Astronomie Millimétrique 30-m telescope, and the Atacama Large Millimeter/submillimeter Array. Ten different absorption lines of CH3OH covering a wide range of sensitivity coefficients Kμ are used to derive a purely statistical 1σ constraint of Δμ/μ=(1.5±1.5)×10−7 for a lookback time of 7.5 billion years. Systematic effects of chemical segregation, excitation temperature, frequency dependence, and time variability of the background source are quantified. A multidimensional linear regression analysis leads to a robust constraint of Δμ/μ=(−1.0±0.8stat±1.0sys)×10−7.


Julija Bagdonaite

M. Dapra

P. Jansen

H. L. Bethlem

Wim Ubachs

Sebastien Muller

Chalmers, Earth and Space Sciences, Onsala Space Observatory

Christian Henkel

K. M. Menten

Physical Review Letters

0031-9007 (ISSN) 1079-7114 (eISSN)

Vol. 111 23 231101-

Advanced Radio Astronomy in Europe (RADIONET3)

European Commission (FP7), 2012-01-01 -- 2015-12-31.

Subject Categories

Physical Sciences

Astronomy, Astrophysics and Cosmology


Basic sciences


Onsala Space Observatory



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