2019MNRAS.487.5175L

Non-standard fields are assumed to be responsible for phenomena attributed to dark energy and dark matter. Being coupled to ordinary matter, these fields modify the masses and/or charges of the elementary particles, thereby violating the weak equivalence principle. Thus, values of fundamental constants such as the proton-to-electron mass ratio, µ, and/or the fine structure constant, α, measured in different environment conditions can be used as probes for this coupling. Here we perform differential measurements of F = µα² to test a non-standard coupling in the Magellanic Clouds-dwarf galaxies where the overall mass budget is dominated by dark matter. The analysis is based on [C I] and CO lines observed with the Herschel Space Observatory. Since these lines have different sensitivities to changes in µ and α, the combined α and µ variations can be evaluated through the radial velocity offsets, ΔV, between the CO and [C I] lines. Averaging over nine positions in the Magellanic Clouds, we obtain <ΔV> = -0.02 ± 0.07 km s^–1, leading to |ΔF/F| < 2 x 10^–7 (1σ), where ΔF/F = (F_obs - F_lab)/F_lab. However, for one position observed with five times higher spectral resolution we find ΔV = -0.05 ± 0.02 km s^–1, resulting in ΔF/F = (-1.7 ± 0.7) x 10^–7. Whether this offset is due to changes in the fundamental constants, due to chemical segregation in the emitting gas, or merely due to Doppler noise requires further investigations.