ar X iv : a st ro - p h / 95 09 15 1 v 1 2 9 Se p 19 95 High - Latitude Galactic Emission in the COBE DMR Two - Year Sky Maps

We cross-correlate the COBE 6 DMR 2-year sky maps with spatial templates from long-wavelength radio surveys and the far-infrared COBE DIRBE maps. We place an upper limit on the spectral index of synchrotron radiation β synch < −2.9 between 408 MHz and 31.5 GHz. We obtain a statistically significant cross-correlation with the DIRBE maps whose dependence on the DMR frequencies indicates a superposition of dust and free-free emission. The high-latitude dust emission (|b| > 30 •) is well fitted by a single dust component with temperature T = 18 +3 −7 K and emissivity ǫ ∝ (ν/ν 0) β with β = 1.9 +3.0 −0.5. The free-free emission is spatially correlated with the dust on angular scales larger than the 7 • DMR beam, with rms variations 5.3 ± 1.8 µK at 53 GHz and angular power spectrum P ∝ ℓ −3. If this correlation persists to smaller angular scales, free-free emission should not be a significant contaminant to measurements of the cosmic microwave anisotropy at degree angular scales for frequencies above 20 GHz. (NASA/GSFC) is responsible for the design, development, and operation of the Cosmic Background Explorer (COBE). Scientific guidance is provided by the COBE Science Working Group. GSFC is also responsible for the analysis software and for the production of the mission data sets.