Super-sample covariance of the thermal Sunyaev-Zel'dovich effect
  The thermal Sunyaev-Zel'dovich (tSZ) effect is a powerful probe of cosmology.
The statistical errors in the tSZ power spectrum measurements are dominated by
the presence of massive clusters in a survey volume that are easy to identify
on individual cluster basis. First, we study the impact of super sample
covariance (SSC) on the tSZ power spectrum measurements, and find that the
sample variance is dominated by the connected non-Gaussian (cNG) covariance
arising mainly from Poisson number fluctuations of massive clusters in the
survey volume. Second, we find that removing such individually-detected,
massive clusters from the analysis significantly reduces the cNG contribution,
thereby leading the SSC to be a leading source of the sample variance. We then
show, based on Fisher analysis, that the power spectrum measured from the
remaining diffuse tSZ effects can be used to obtain tight constraints on
cosmological parameters as well as the hydrostatic mass bias parameter. Our
method offers complementary use of individual tSZ cluster counts and the power
spectrum measurements of diffuse tSZ signals for cosmology and intracluster gas
physics.
