Current constraints on the n–Ω_M parameter space for flat universes with Ω_Λ ≠ 0. Left panels: black solid curves show the one, two, and three sigma confidence levels in the two-dimensional plane, while the color map depict the reduced chi-square. Right panels: one-dimensional posterior likelihoods for Ω_M. Top and bottom panels correspond to the two choices of priors discussed in the text.