NONCOSMOLOGICAL SIGNAL CONTRIBUTIONS TO THE COBE1 DMR ANISOTROPY MAPS

We examine the COBE Differential Microwave Radiometer (DMR) data for evidence of noncosmological source contributions. The DMR maps are cross-correlated with maps of rich clusters, extragalactic IRAS sources, HEAO 1 A-2 X-ray emission, and 5 GHz radio sources. We limit the rms contributions from these sources on a 7-degrees angular scale to less than 10 muK (95% confidence level) in the DMR maps, although the Large Magellanic Cloud probably contributes approximately 50 muK to a limited region of the sky. Thus, our previous interpretation that the fluctuations in the COBE DMR data are most likely due to cosmic fluctuations at the surface of last scattering remains intact. The Comptonization parameter for hot electrons traced by rich clusters is limited to deltay < 2 x 10(-6) (95% confidence level) averaged over the 7-degrees DMR beam.