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Galactic Foreground cleaning in gamma-rays

The workshop held on June 23, 2010, focused on the complexities of cleaning galactic foregrounds in gamma-ray data, particularly in relation to Cosmic Microwave Background (CMB) observations. Led by prominent researchers, including Alessandro Cuoco from the Oskar Klein Center, the session explored the contamination of WMAP data by galactic signals. Participants discussed various template fitting techniques for synchrotron, free-free, and dust emissions, emphasizing the challenges faced in accurately subtracting these foregrounds. The implications of the WMAP Haze were also analyzed in the context of foreground removal strategies.

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Galactic Foreground cleaning in gamma-rays

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  1. Galactic Foreground cleaning in gamma-rays Anisotropy Workshop, June 23th 2010 Alessandro Cuoco, Oskar Klein Center, Stockholm University

  2. The Microwave sky • In addition to CMB photons, WMAP data is “contaminated” by a number of galactic foregrounds that must be accurately subtracted • The WMAP frequency range is well suited to minimize the impact of foregrounds • Substantial challenges are involved in identifying and removing foregrounds

  3. Template fitting

  4. Synchrotron: Template: C.G.T. Haslam et al., A&A 100 (1981) 209. Synchrotron + Freefree: Template: D.P. Finkbeiner, ApJS 146 (2003) 407. Free-free + Dust:Template: D.P. Finkbeineret al., ApJ 524 (1999) 867. T & S Dust WMAP + TOTAL CMB CMB: Gold et al., arXiV:1001.4555.

  5. The “WMAP Haze” D. P. Finkbeiner, Astrophys. J. 614 (2004) 186 G. Dobler and D. P. Finkbeiner, arXiv:0712.1038 [astro-ph]. After known foregrounds are subtracted, an excess appears in the residual maps within the inner ~20 around the Galactic Center

  6. WMAP Team foreground analysis and the Haze The fit procedure used for the haze extraction is quite important, and using more degrees of freedom to model the foregrounds as performed by the WMAP team fails in finding the feature. They still find an hardening of the synchrotron emission in the Haze region, though. Map of the synchrotron spectral indexes in a pixel by pixel fit procedure by WMAP Synchrotron spectral indexes averaged along constant longitudes stripes by WMAP WMAP Collaboration (B. Gold et al.) 2008 [arXiv:astro-ph/0803.0715]. D.T. Cumberbatch,, arXiv:0902.0039 [astro-ph].

  7. The Gamma Sky • Galactic Contribution from: • Pion Decay • Inverse Compton • Electron Bremsstrahlung Galprop Foregrounds Model: Moskalenko et al.

  8. Morphology of the gamma-sky components

  9. A Fermi Haze? Dobler, Finkbeiner et al. 2009

  10. Further directions: Multi-template fitting using gas rings?

  11. More directions: Planck dust map(s) as gas templates

  12. Lot of work to do…

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