An Anomalous Component of Galactic Emission

We present results from microwave background observations at the Owens Valley Radio Observatory. These observations, at 14.5 and 32 GHz, are designed to detect intrinsic anisotropy on scales of 7'-22'. After point-source removal, we detect significant emission with temperature spectral index β ≃ -2 toward the north celestial pole (NCP). Comparison of our data with the IRAS 100 μm map of the same fields reveals a strong correlation between this emission and the infrared dust emission. From the lack of detectable Hα emission, we conclude that the signals are consistent either with flat-spectrum synchrotron radiation or with free-free emission from T e ≳ 10 6 K gas, probably associated with a large H I feature known as the NCP Loop. Assuming β = -2.2, our data indicate a conversion T f / I 100μm = 7.5 × 10 -2 ν K (MJy sr -1 ) -1 . The detection of such a component suggests that we should be cautious in any assumptions made regarding foregrounds when designing experiments to map the microwave background radiation.