Robustness of the Pairwise Kinematic Sunyaev–Zeldovich Power Spectrum Shape as a Cosmological Gravity Probe

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Abstract We prove from the modified gravity (MG) galaxy/halo mock catalogs that the shape of the pairwise kinematic Sunyaev–Zeldovich (kSZ) power spectrum P kSZ has constraining power on discriminating different gravity theories on cosmological scales. By varying the effective optical depth τ T as a free parameter, we verify that the τ T-f (the linear growth rate) degeneracy in the linear theory of P kSZ is broken down by the nonlinear structure growth and the scale dependence of f in some MG theories. Equivalently speaking, the shape of P kSZ alone could be used to tightly constrain the MG theories on cosmological scales. With good knowledge of galaxy density biases, we verify that a combination of the next-generation galaxy spectroscopic redshift and CMB surveys, e.g., BOSS+CMB-S4 or DESI+CMB-S4, could potentially discriminate f(R) models from the general relativity at the ∼5σ level using the shape of the galaxy pairwise kSZ dipole P kSZ,ℓ = 1 alone, when f R0 = 10−4.