Abstract
Non-Gaussian (NG) statistics of the thermal Sunyaev-Zeldovich (tSZ) effect carry significant information which is not contained in the power spectrum. Here, we perform a joint Fisher analysis of the tSZ power spectrum and bispectrum to verify how much the full bispectrum can contribute to improve parameter constraints. We go beyond similar studies of this kind in several respects: first of all, we include the complete power spectrum and bispectrum (auto- and cross-) covariance in the analysis, computing all NG contributions; furthermore we consider a multi-component foreground scenario and model the effects of component separation in the forecasts; finally, we consider an extended set of both cosmological and intra-cluster medium parameters. We show that the tSZ bispectrum is very efficient at breaking parameter degeneracies, making it able to produce even stronger cosmological constraints than the tSZ power spectrum: e.g. the standard deviation on σ8 shrinks from σPS(σ8)=0.35 to σBS(σ8)=0.065 when we consider a multi-parameter analysis. We find that this is mostly due to the different response of separate triangle types (e.g. equilateral and squeezed) to changes in model parameters. While weak, this shape dependence is clearly non-negligible for cosmological parameters, and it is even stronger, as expected, for intra-cluster medium parameters.
Highlights
The thermal Sunyaev-Zeldovich effect [1, 2] [3, for a recent review] is a spectral distortion of the Cosmic Microwave Background (CMB), mostly generated in galaxy clusters by inverse Compton scattering of CMB photons off hot electrons
One of the advantages of the thermal Sunyaev-Zeldovich (tSZ) power spectrum analysis is that it allows including small, unresolved clusters, and it does not require direct measurements of cluster masses. As it has been argued long before the tSZ was routinely measured across the sky [12], it is important to notice that the tSZ map is highly non-Gaussian, only a part of the available tSZ information is captured by the power spectrum
The tSZ power spectrum is given by the sum of the Poisson one-halo term, which account for intra-halo correlations, and the two-halo term which models inter-halo correlations [7, 27]
Summary
The thermal Sunyaev-Zeldovich (tSZ) effect [1, 2] [3, for a recent review] is a spectral distortion of the Cosmic Microwave Background (CMB), mostly generated in galaxy clusters by inverse Compton scattering of CMB photons off hot electrons. A later study [16] combined cluster counts with power spectrum and equilateral (all three ’s equal) bispectrum measurements, showing that the bispectrum — even just by considering the small equilateral triangle subset — can play a significant role in breaking (cosmological and astrophysical) parameter degeneracies.
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