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Planck intermediate results. XII. Diffuse Galactic components in the Gould Belt system

Planck intermediate results. XII. Diffuse Galactic components in the Gould Belt system

Publication date: 29 August 2013

Authors: Planck Collaboration

Journal: Astronomy & Astrophysics
Volume: 557, September 2013
Page: A53
Year: 2013

Copyright: ESO, 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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