Limits on arcsecond-scale fluctuations in the cosmic microwave background

The authors used the NRAO Very Large Array in its C configuration at a wavelength of 6 cm to set upper limits on the rms fluctuation of sky brightness on angular scales of 6arcsec - 18arcsec from sources too weak to be detected individually. At the highest resolution, they establish a limit of 8 μJy per beam area on the rms sky fluctuation. If this fluctuation level is the result of a Poisson distribution of unresolved sources, each of flux density S₀ Jy, then the number density of such sources per steradian must be less than 0.08 S₀^-2sr^-1. These limits also establish limits on the rms temperature fluctuation for simple models of fluctuations in the cosmic microwave background.