Planck intermediate results. XII: Diffuse Galactic components in the Gould Belt system
2013
We perform an analysis of the diffuse low-frequency Galactic components in the southern
part of the Gould Belt system (130° ≤ l ≤ 230° and
−50° ≤ b ≤ −10°). Strong ultra-violet flux
coming from the Gould Belt super-association is responsible for bright diffuse foregrounds
that we observe from our position inside the system and that can help us improve our
knowledge of the Galactic emission. Free-free emission and anomalous microwave emission
(AME) are the dominant components at low frequencies
(ν < 40 GHz), while synchrotron emission is
very smooth and faint. We separated diffuse free-free emission and AME from synchrotron
emission and thermal dust emission by using Planck data, complemented by
ancillary data, using the correlated component analysis (CCA) component-separation method
and we compared our results with the results of cross-correlation of foreground templates
with the frequency maps. We estimated the electron temperature
Te from Hα and free-free emission using two
methods (temperature-temperature plot and cross-correlation) and obtained
Te ranging from 3100 to 5200K for an effective fraction of
absorbing dust along the line of sight of 30% (fd = 0.3). We
estimated the frequency spectrum of the diffuse AME and recovered a peak frequency (in
flux density units) of 25.5 ± 1.5 GHz. We verified the reliability of this result with
realistic simulations that include biases in the spectral model for the AME and in the
free-free template. By combining physical models for vibrational and rotational dust
emission and adding the constraints from the thermal dust spectrum from
Planck and IRAS, we are able to present a good description of the AME
frequency spectrum for plausible values of the local density and radiation field.
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