Separation of anomalous and synchrotron emissions using WMAP polarization data
By M. Miville-Deschênes, N. Ysard, A. Lavabre, N. Ponthieu, J. Macías-Pérez, J. Aumont, J. Bernard. 2008
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Context. Apart from its contribution to cosmology, the WMAP data brings new information on the Galactic interstellar medium. In particular the polarization data provide constraints on the Galactic magnetic field and the synchrotron emission, while the intensity data can be used to study the anomalous microwave emission. Aims. The main goals of this study is to use the information from both WMAP intensity and polarization data to do a separation of the Galactic components, with a focus on the synchrotron and anomalous emissions. Methods. Our analysis is made at 23 GHz where the signal-to-noise ratio is the highest and the estimate of the CMB map is less critical. Our estimate of the synchrotron intensity is based on an extrapolation of the Haslam 408 MHz data with a spatially varying spectral index constrained by the WMAP 23 GHz polarization data and a bi-symmetrical spiral model of the galactic magnetic field with a turbulent part following a –5/3 power law spectrum. Results. The 23 GHz polarization data are found to be compatible with a magnetic field with a pitch angle p = −8.5 ◦ and an amplitude of the turbulent part of the magnetic field 0.57 times the local value of the field, in agreement with what is found using rotation measures of pulsars and polarized extinction by dust. The synchrotron spectral index between 408 MHz and 23 GHz obtained from polarization data and our model of the magnetic field has a mean value of βs = −3.00 with a limited spatial variation with a standard deviation of 0.06. When thermal dust, free-free and synchrotron are removed from the WMAP intensity data, the residual anomalous emission is highly correlated with thermal dust emission with a spectrum in agreement with spinning dust models. Conclusions. Considering a classical model of the large scale Galactic magnetic field, we show that the polarization data of WMAP are in favor of a soft synchrotron intensity highly correlated with the 408 MHz data. Furthermore the combination of the WMAP polarization and intensity data brings strong evidence for the presence of unpolarized spinning dust emission in the 20–60 GHz range. In preparation for the Planck mission this joint analysis of polarization and intensity data opens new perspective on the study of the Galactic interstellar medium and on the component separation exercise.
Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/6c27b37164011e1510679dc073519f4f7715a26d
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Citations in the corpus
- AN IMPRINT OF MOLECULAR CLOUD MAGNETIZATION IN THE MORPHOLOGY OF THE DUST POLARIZED EMISSION (2013, unknown): “…ON M5S 3H8, Canada 4 Institut d’Astrophysique Spatiale CNRS, Université ParisSud, bâtiment 121, 91405, Orsay, France 5 Department of Physics, University of Toronto, 60 St. George Street, Toronto, ON M5S 1A7, Canada sion (Beuermann et al. 1985; Miville-Deschênes et al. 2008; Jaffe et al. 2010).”
- Planck 2018 results (2018, methodology): “The pixel-dependent spectral index is derived from an analysis of WMAP data by Miville-Deschênes et al. (2008).”
- Planck intermediate results. XXII. Frequency dependence of thermal emission from Galactic dust in intensity and polarization (2014, methodology): “The derived mean βs of the dust-correlated synchrotron emission is consistent with the spectral index of 408-MHz-correlated synchrotron emission obtained using WMAP data (Miville-Deschênes et al. 2008; Dickinson et al. 2009; Gold et al. 2011; Ghosh et al. 2012), and the spectral index of the polariz”
- The interstellar cosmic-ray electron spectrum from synchrotron radiation and direct measurements. (2011, methodology): “10 Miville-Deschênes et al. (2008) used the 408 MHz maps uncorrected for zero offset (Miville-Deschênes, priv. comm.), so we use the same maps for consistency when applying their index maps.”
- Galactic synchrotron emission with cosmic ray propagation models (2013, methodology): “The Miville-Deschênes et al. (2008) total synchrotron maps are used to compare our model to the total synchrotron.”
- The pre-launch Planck Sky Model: a model of sky emission at submillimetre to centimetre wavelengths (2012, methodology): “…on the sky (set to –3.0 by default); 2. the spectral index map of Giardino et al. (2002) obtained us- ing a combination of 408, 1420 and 2326 MHz data; 3. the spectral index map provided by model 4 of Miville-Deschênes et al. (2008) obtained using a combination of the 408 MHz and WMAP 23 GHz data.”
- Planck intermediate results. XIX. An overview of the polarized thermal emission from Galactic dust (2014, methodology): “Figure 7 shows the distribution of p as a function of the polarization geometrical efficiency factor gd, in particular the polarization fraction computed for the bi-symmetrical spiral model of the magnetic field on large scales from Miville-Deschênes et al. (2008).”