The recent discovery of two flux decrements in deep radio maps obtained by the VLA and the Ryle Telescope can have powerful implications for the density parameter of the Universe , \Omega _ { o } .
We outline these implications by modeling the decrements as the thermal Sunyaev–Zel ’ dovich ( SZ ) effect from two clusters assuming their properties are similar to those of the low redshift population .
In this case , the absence of any optical or X–ray counterparts argues that the clusters must be at large redshifts .
We highlight the difficulty this poses for a critical cosmology by a comparison with a fiducial open model with \Omega _ { o } = 0.2 ( \lambda _ { o } = 0 ) .
Applying the phenomenological X–ray luminosity–temperature relation needed to explain the EMSS cluster redshift distribution , as inferred by Oukbir and Blanchard ( 1997 ) , we convert the X–ray band upper limits to lower limits on the clusters ’ redshifts .
Comparison of the counts implied by these two SZ detections with model predictions , for clusters with redshifts larger than these lower limits , illustrates quantitatively the inability of the critical cosmology to account for such high–redshift clusters .
On the other hand , the open model with \Omega _ { o } = 0.2 remains consistent with the existence of the two objects ; it possibly has , however , difficulties with current limits on spectral distortions and temperature fluctuations of the cosmic microwave background .
The discussion demonstrates the value of SZ cluster searches for testing cosmological models and theories of structure formation .