A new approach for testing variations of fundamental constants over cosmic epochs using FIR fine-structure lines

TL;DR

This paper introduces a more sensitive method using FIR fine-structure lines to test for variations in fundamental constants over cosmic time, providing limits consistent with no change over 13 billion years.

Contribution

A novel approach comparing FIR fine-structure lines and CO transitions to improve sensitivity in measuring fundamental constant variations.

Findings

Limits on alpha^2/mu variation are consistent with no change over 13 Gyr.

Method is ten times more sensitive than previous QSO metal absorption line techniques.

Future observations could improve current limits by an order of magnitude.

Abstract

Aims. To obtain limits on the variation of the fine-structure constant alpha and the electron-to-proton mass ratio mu over different cosmological epochs. Methods. A new approach based on the comparison of redshifts of far infrared (FIR) fine-structure lines and low-lying rotational transitions in CO is proposed which is in principle more sensitive by a factor of 10 compared to QSO metal absorption lines. Results. Estimations of the quotient F = alpha^2/mu obtained for two distant quasars J1148+5251 (z = 6.42) and BR1202-0725 (z = 4.69) provide Delta F/F = (0.1+/-1.0)10^{-4} and (1.4+/-1.5)10^{-4}, respectively. The obtained limits are consistent with no variation of physical constants at the level of 0.01% over a period of 13 Gyr. Conclusions. Upcoming observations of quasars and distant galaxies in FIR fine-structure lines of different species and in CO low rotational lines at the SOFIA, HSO, and ALMA are expected to improve the current limit by, at least, an order of magnitude.