Microwave Emission at High Galactic Latitudes in the Four-Year DMR Sky Maps

Abstract

We use the COBE Differential Microwave Radiometers (DMR) 4 yr sky maps to model Galactic microwave emission at high latitudes (|b| > 20°). Cross-correlation of the DMR maps with Galactic template maps detects fluctuations in the high-latitude microwave sky brightness with the angular variation of the DIRBE far-infrared dust maps and a frequency dependence consistent with a superposition of dust and free-free emission. We find no significant correlations between the DMR maps and various synchrotron templates. On the largest angular scales (e.g., quadrupole), Galactic emission is comparable in amplitude to the anisotropy in the cosmic microwave background (CMB). The CMB quadrupole amplitude, after correction for Galactic emission, has amplitude Q_rms = 10.7 μK with random uncertainty 3.6 μK and systematic uncertainty 7.1 μK from uncertainty in our knowledge of Galactic microwave emission.