2006/11/30 by S. P. Boughn, J. C. Pober
Physics and Astronomy · #Astro and Planetary Science #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #astro-ph
paper · pdf · doi:10.1086/516817
published as Astrophys.J.661:938-943,2007 · 11 page, 3 figures
openalex publication_date 2007/05/29 · arxiv created 2007/06/01 · arxiv updated 2011/02/11 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
A comparison of a 19 GHz full-sky map with the WMAP satellite K-band (23 GHz) map indicates that the bulk of the 20 GHz emission within 7° of the Galactic plane has an inverted (rising) spectrum with an average spectral index α = 0.21 ± 0.05. While such a spectrum is inconsistent with steep-spectrum synchrotron (α ~ -0.7) and flat-spectrum free-free (α ~ -0.1) emission, it is consistent with various models of electric dipole emission from thermally excited spinning dust grains, as well as models of magnetic dipole emission from ferromagnetic dust grains. Several regions in the plane, e.g., near the Cygnus arm, have spectra with even larger α. While the low signal-to-noise ratio of the 19 GHz data precludes a detailed map of the spectral index, especially off the Galactic plane, it appears that the bulk of the emission in the plane is correlated with the morphology of dust. Regions with higher 23 GHz flux tend to have harder spectra. Off the plane, at Galactic latitudes 7° < | b | < 20°, the spectrum steepens to α = -0.16 ± 0.15.