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.
Highlights
The first year of data from the Wilkinson Microwave Anisotropy Probe (WMAP) has sparked a revolution in the study of cosmology and the early universe ( Bennett et al 2003; Hinshaw et al 2003; Spergel et al 2003)
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)
The WMAP team relied on a maximum entropy method ( MEM ) analysis to determine that spinning dust2 with the Draine & Lazarian (1998) cold neutral medium (CNM ) spectrum accounts for less than 5% of the emission in any WMAP waveband
Summary
The first year of data from the Wilkinson Microwave Anisotropy Probe (WMAP) has sparked a revolution in the study of cosmology and the early universe ( Bennett et al 2003; Hinshaw et al 2003; Spergel et al 2003) It has provided full-sky maps of the interstellar medium at 23– 94 GHz at a sensitivity of $200 K per 70 pixel at resolutions much higher than previous full-sky observations. We emphasize that the WMAP team’s primary objective was to prevent Galactic foreground emission from contaminating their cosmological results based on the cosmic microwave background (CMB) anisotropy. They have done a superb job of modeling the foregrounds, regardless of whether the physical. As the polarization data are not yet public, discussion of polarization will be deferred to a later paper
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