http://arxiv.org/abs/1805.11607

The key to understand the nature of dark energy relies 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 4 different realisations of a Hu & Sawicki $f(R)$ gravity model, parametrised by the values of $\overline{f}{\rm R,0}=(0,-10^{-6},-10^{-5},-10^{-4})$, to compute the properties of the kSZ effect due to the ionized Universe and how they depend on $\overline{f}{\rm R,0}$ and on the redshift of reionization, $z_{\rm re}$. In the standard General Relativity limit ($\overline{f}{\rm R,0}$=0) we obtain an amplitude of the kSZ power spectrum of $\mathcal{D}^{\rm kSZ}{3000}=4.1\,$$\mu$K$^2$ ($z_{\rm re}$=8.8), close to the $+1\sigma$ limit of the $\mathcal{D}^{\rm kSZ}{3000}=(2.9\pm1.3)\,$$\mu$K$^2$ measurement by SPT. This corresponds to an upper limit on the kSZ contribute from patchy reionization of $\mathcal{D}^{\rm kSZ,patchy}{3000}<0.9\,$$\mu$K$^2$ (95 per cent confidence level). Modified gravity boosts the kSZ signal by about 3, 12 and 50 per cent for $\overline{f}{\rm R,0}=(-10^{-6},-10^{-5},-10^{-4})$, respectively, with almost no dependence on the angular scale. This means that with modified gravity the limits on patchy reionization shrink significantly: for $\overline{f}{\rm R,0}=-10^{-5}$ we obtain $\mathcal{D}^{\rm kSZ,patchy}{3000}<0.4\,$$\mu$K$^2$. Finally, we provide an analytical formula for the scaling of the kSZ power spectrum with $z{\rm re}$ and $\overline{f}{\rm R,0}$ at different multipoles: at $\ell=3000$ we obtain $\mathcal{D}^{\rm kSZ}{3000}\propto z_{\rm re}^{0.24}\left(1+\sqrt{\left|\overline{f}_{\rm R,0}\right|}\right)^{41}$.

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M. Roncarelli, M. Baldi and F. Villaescusa-Navarro
Wed, 30 May 18
5/65

Comments: 11 pages, 5 figures, 2 tables