Constraints on the ζ–w₀ plane for our simulated data sets, with β marginalised. The blue contours are for a ΛCDM fiducial, while the red ones are for a fiducial model with w₀ = −0.95 and ζ = 0. For the latter fiducial, left and right columns of panels correspond to β = −0.8 and β = +0.8, respectively, while top, middle, and bottom rows correspond to different sensitivities in the α data set, respectively σ = 5, 1, and 0.1 ppm. One, two, and three-sigma confidence levels are shown in all panels.