Constraints on structure formation models from the Sunyaev-Zel'dovich effect

In the context of cold dark matter (CDM) cosmological models, we have simul ated images of the brightness temperature fluctuations in the cosmic microw ave background (CMB) sky owing to the Sunyaev-Zel'dovich (S-Z) effect in a cosmological distribution of clusters. We compare the image statistics with recent ATCA limits on arcmin-scale CMB anisotropy. The S-Z effect produces a generically non-Gaussian field and we compute the variance in the simula ted temperature-anisotropy images, after convolution with the ATCA beam pat tern, for different cosmological models. All the models are normalized to t he 4-yr COBE data. We find an increase in the simulated-sky temperature var iance with increase in the cosmological density parameter Omega(0). A compa rison with the upper limits on the sky variance set by the ATCA appears to rule out our closed-universe model: low-Omega(0) open-universe models are p referred. The result is independent of any present day observations of sigm a(8).