Cosmology from the thermal Sunyaev-Zel'dovich power spectrum: Primordial non-Gaussianity and massive neutrinos

We carry out a comprehensive analysis of the possible constraints on cosmological and astrophysical parameters achievable with measurements of the thermal Sunyaev-Zel’dovich (tSZ) power spectrum from upcoming full-sky cosmic microwave background observations, with a particular focus on one-parameter extensions to the ΛCDM standard model involving local primordial non-Gaussianity (described by f_NL) and massive neutrinos (described by M_ν). We include all of the relevant physical effects due to these additional parameters, including the change to the halo mass function and the scale-dependent halo bias induced by local primordial non-Gaussianity. We use the halo model to compute the tSZ power spectrum and provide a pedagogical derivation of the one- and two-halo terms in an Appendix. We model the pressure profile of the intracluster medium (ICM) using a parametrized fit that agrees well with existing observations, and include uncertainty in the ICM modeling by including the overall normalization and outer logarithmic slope of the profile as free parameters. We compute forecasts for Planck, Primordial Inflation Explorer (PIXIE), and a cosmic variance (CV)-limited experiment, using multifrequency subtraction to remove foregrounds and implementing two masking criteria based on the ROSAT and eROSITA cluster catalogs to reduce the significant CV errors at low multipoles. We find that Planck can detect the tSZ power spectrum with >30σ significance, regardless of the masking scenario. However, neither Planck or PIXIE is likely to provide competitive constraints on f_NL from the tSZ power spectrum due to CV noise at low ℓ overwhelming the unique signature of the scale-dependent bias. A future CV-limited experiment could provide a 3σ detection of f_NL≃37, which is the WMAP9 maximum-likelihood result. The outlook for neutrino masses is more optimistic: Planck can reach levels comparable to the current upper bounds ≲0.3eV with conservative assumptions about the ICM; stronger ICM priors could allow Planck to provide 1σ-2σ evidence for massive neutrinos from the tSZ power spectrum, depending on the true value of the sum of the neutrino masses. We also forecast a <10% constraint on the outer slope of the ICM pressure profile using the unmasked Planck tSZ power spectrum.