Microwave Interstellar Medium Emission Observed by theWilkinson Microwave Anisotropy Probe

Abstract

We investigate the nature of the diffuse Galactic emission in the Wilkinson Microwave Anisotropy Probe (WMAP) temperature anisotropy data. Substantial dust-correlated emission is observed at all WMAP frequencies, far exceeding the expected thermal dust emission in the lowest frequency channels (23, 33, and 41 GHz). The WMAP team interprets this emission as dust-correlated synchrotron radiation, attributing the correlation to the natural association of relativistic electrons produced by supernovae (SNe) with massive star formation in dusty clouds, and deriving an upper limit of 5% on the contribution of Draine & Lazarian spinning dust to the K band (23 GHz). We pursue an alternative interpretation that much, perhaps most, of the dust-correlated emission at these frequencies is indeed spinning dust, and explore the spectral dependence on environment by considering a few specific objects as well as the full-sky average. Models similar to Draine & Lazarian spinning dust provide a good fit to the full-sky data. The full-sky fit also requires a significant component with a flat spectrum uncorrelated with Hα, possibly hot (~106 K) gas within 30° of the Galactic center.