Cosmology with the kinetic Sunyaev–Zeldovich effect: Independent of the optical depth and σ8

Cosmological constraints obtained by the kinetic Sunyaev–Zeldovich experiments are degenerate with the optical depth measurement – an effect that is commonly known as the optical-depth degeneracy. In this work, we introduce a new statistic based on the first moment of relative velocity between pairs in a triplet, which is capable of constraining cosmological parameters independently of the optical depth and of σ8. Using 22 000 N-body simulations from the Quijote suite, we quantified the information content in the new statistic using Fisher matrix forecast. We find that it is able to obtain strong constraints on the cosmological parameters, particularly on the summed neutrino mass. The constraints bring an improvement on all cosmological model parameters by a factor of 6.2–12.9 and 2.3–5.7 when compared to those obtained from the mean pairwise velocity and from the redshift-space halo power spectrum, respectively. Thus, this new statistic paves a way forward in constraining cosmological parameters independent of the optical depth and σ8 when using data from future kinetic Sunyaev–Zeldovich experiments alone.