The kinematic Sunyaev-Zel’dovich effect of the large-scale structure (II): the effect of modified gravity

The key to understand the nature of dark energy lies in our ability to probe the distant Universe. In this framework, the recent detection of the kinematic Sunyaev-Zel'dovich (kSZ) effect signature in the cosmic microwave background obtained with the South Pole Telescope (SPT) is extremely useful since this observable is sensitive to the high-redshift diffuse plasma. We analyse a set of cosmological hydrodynamical simulation with four different realizations of a Hu & Sawicki f(R) gravity model, parametrized by the values of (f) over bar (R,0)= (0, -10(-6) , -10(-5) , -10(-4 )), to compute the properties of the kSZ effect due to the ionized Universe and how they depend on (f) over bar (R,0) and on the redshift of reionization, z(re) . In the standard General Relativity limit ((f) over bar (R,0) = 0) we obtain an amplitude of the kSZ power spectrum of D-3000(kSZ)= 4.1 mu K (2) (z(re)= 8.8), close to the +1 sigma limit of the D-3000(kSZ )= (2.9 +/- 1.3) mu K-2 measurement by SPT. This corresponds to an upper limit on the kSZ contribute from patchy reionization of <b>D-3000(kSZ,patchy) < 0.9 mu K-2 (95 per cent confidence level). Modified gravity boosts the kSZ signal by about 3, 12, and 50 per cent for (f) over bar (R,0)=(- 10(-6) , -10(-5) , -10(-4) ), respectively, with almost no dependence on the angular scale. This means that with modified gravity the limits on patchy reionization shrink significantly: for (f) over bar (R,0) =-10(-5) we obtain D-3000(kSZ,patchy) < 0.4 mu K (2) . Finally, we provide an analytical formula for the scaling of the kSZ power spectrum with z(re) and (f) over bar (R,0) at different multipoles: at l = 3000 we obtain D-3000(kSZ) proportional to z(re)(0.24) (1 + root vertical bar(f) over bar (R,0)vertical bar)(41).