Identification of Spinning Dust in Halpha-Correlated Microwave Emission

Abstract

CMB experiments commonly use maps of Halpha intensity as a spatial template for Galactic free-free emission, assuming a power law I_nu \propto nu^-0.15 for the spectrum. Any departure from the assumed free-free spectrum could have a detrimental effect on determination of the primary CMB anisotropy. We show that the Halpha-correlated emission spectrum in the diffuse warm ionized medium (WIM) is not the expected free-free spectrum at WMAP frequencies. Instead, there is a broad bump in the spectrum at ~50 GHz which is consistent with emission from spinning dust grains. Spectra from both the full sky and smaller regions of interest are well fit by a superposition of a free-free and WIM Draine & Lazarian (1998) spinning dust model, shifted in frequency. The spinning dust emission is ~5 times weaker than the free-free component at 50 GHz, with the null hypothesis that the Halpha-correlated spectrum is pure free-free, ruled out at >8 sigma in all regions and >100 sigma for the full sky fit.

8 pages, 5 figures; submitted to ApJ; LaTeX modified slightly to reveal missing Figure 5

References in corpus (5)

• Three Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Polarization Analysis
• Three-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Temperature Analysis
• Extended Anomalous Foreground Emission in the WMAP 3-Year Data
• AMI limits on 15 GHz excess emission in northern HII regions
• An upper limit on anomalous dust emission at 31 GHz in the diffuse cloud [LPH96]201.663+1.643

Cited by in corpus (5)

• Extended Anomalous Foreground Emission in the WMAP 3-Year Data
• Constraining Spinning Dust Parameters with the WMAP Five-Year Data
• Bayesian component separation and CMB estimation for the 5-year WMAP temperature data
• The C-Band All-Sky Survey (C-BASS): Template Fitting of Diffuse Galactic Microwave Emission in the Northern Sky
• Cosmic ray backgrounds for dark matter indirect detection