Confusion Limit to the Measurement of the Sunyaev-Zeldovich Effect in Clusters of Galaxies at Millimeter Wavelengths
Session 5 -- Cosmology and Gravitational Lenses
Display presentation, Monday, 9:20-6:30, Heller Lounge Room

## [5.10] Confusion Limit to the Measurement of the Sunyaev-Zeldovich Effect in Clusters of Galaxies at Millimeter Wavelengths

M. L. Fischer, T. R. Ho, and A. E. Lange (Physics Dept., UC Berkeley)

We present estimates of the confusion limit to observations of the thermal and kinetic Sunyaev-ZelUdovich (S-Z) effects on arcminute angular scales at millimeter wavelengths. Measurements of the amplitude of the thermal S-Z effect (Comptonization) can be combined with measurements of the X- ray brightness of the cluster to yield values for the Hubble constant, Ho. The ratio of the kinetic and the thermal S-Z effects can be combined with the X-ray gas temperature to yield the radial component of the peculiar velocity of the cluster. The confusion noise to measurement of the thermal S-Z effect has minima at frequencies near 100 and 300 GHz. The estimated 1$\sigma$ noise level for measurements of the Compton y parameter are $\Delta$y J$= 10^{-6}$ and $6 x 10^{-6}$ respectively. For a Compton parameter typical of a rich cluster, y = $10^{-4}$ , the contribution of confusion to the uncertainty in an estimate of Ho will be 2$\Delta$y/y = 2\% and 12\% respectively. The confusion noise to measurement of the kinetic S-Z effect has a broad minimum near 100 GHz. The estimated 1$\sigma$ noise level for measurements of the radial component of the peculiar velocity is $\Delta v_{r} = 50 (\tau /0.01)^{-1}$ kms$^{-1}$, where $\tau$ is the optical depth for scattering of the CMB photons. The estimated confusion limit assumes an ideal experiment that suffers no beam dilution, and measures the cluster brightness relative to a reference beam that is sufficiently far from the cluster that it contains negligible S-Z signal. The confusion limits for an actual experiment will be increased by these two factors.