CROSS-CORRELATION BETWEEN THE 170 GHZ SURVEY MAP AND THE COBE DIFFERENTIAL MICROWAVE RADIOMETER 1ST-YEAR MAPS

This Letter describes results of a cross-correlation between the 170 G Hz partial-sky survey, made with a 3.8-degrees beam balloon-borne inst rument, and the COBE DMR ''Fit Technique'' reduced galaxy all-sky map with a beam of 7-degrees. The strong correlation between the data sets implies that the observed structure is consistent with thermal variat ions in a 2.7 K emitter. We describe a number of tests of the correlat ion: (1) A chi2 analysis applied to the correlation function rules out the assumption that there is no structure in either of the two maps. (2) A second test shows that if the DMR map has structure but the 170 GHz map does not, the probability of obtaining the observed correlatio n is small. (3) Further analyses support the assumption that both maps have structure and that the 170 GHz-DMR cross-correlation is consiste nt with the analogous DMR correlation function. (4) Maps containing va rious combinations of noise and Harrison-Zel'dovich power spectra are simulated and correlated to reinforce the result. Because these two ex periments use completely different observing strategies, observing fre quencies, and data reduction methods, the correlation provides compell ing evidence that both instruments have observed fluctuations consiste nt with anisotropies in the cosmic microwave background.