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Dust polarization expectations The PILOT experiment

Dust polarization at long wavelengths. J.-Ph. Bernard CESR Toulouse. Dust polarization expectations The PILOT experiment. J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26 th 2006. Dust Polarization. ° Measured in absorption in the visible. Matthewson & Ford 1970.

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Dust polarization expectations The PILOT experiment

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  1. Dust polarization at long wavelengths J.-Ph. Bernard CESR Toulouse • Dust polarization expectations • The PILOT experiment J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006

  2. Dust Polarization ° Measured in absorption in the visible Matthewson & Ford 1970 ° Measured in emission in the FIR/mm (ground, Archeops, Boomerang) 850 mm OMC-3 in Orion A J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006

  3. Lessons from extinction UV extinction IR extinction UV rise (PAH) is not polarized Bump (VSG) is not polarized - Visible extinction (BG) is polarized- 10 mm absorption feature is polarized- 3.4 mm ice feature is polarized So, small (Carbonaceous) grain emission is not expected to be polarized while large (Silicate) grains is. J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006 Desert et al 1990

  4. Complications ... Model by Finkbeiner, Davis, Schlegel (FDS) mm excess: - FIRAS data show b=1.7near the Galactic plane- WMAP data show that this extends down to l>2-3 mm warm dust (graphite ?) cold dust (silicate ?) T1=9.6 K, b1=1.5T2=16.4 K, b2=2.6 100 mm 1 mm 10 mm J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006

  5. Complications ... Model by Finkbeiner, Davis, Schlegel (FDS) mm excess: - FIRAS data show b=1.7near the Galactic plane- WMAP data show that this extends down to l>2-3 mm warm dust (graphite ?) cold dust (silicate ?) T1=9.6 K, b1=1.5T2=16.4 K, b2=2.6 Would imply a polarizationdegree highly variable with wavelength X-foreground = magnetic dipoleemission from vibrating dust X-foreground =spinning small dust J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006

  6. Alternative Models Meny et al. in prep. Two-Level Systems In principle, such models predict no large change of polarization with wavelength J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006

  7. FDS TLS Alternative Models DCD+TLS Model DCD TLS: resonant TLS: hoping Best fit: J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006

  8. FIR/submm Observations ? Dust polarization certainly varies with l in some (dense to very dense) objects ... From Vaillancourt et al. J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006

  9. FIR/submm Observations ? From Vaillancourt et al. ... but the observed variations match none of the models.Indeed, they could be entirely due to confusion on line-of-sight, so ..We have no clue if it varies in the diffuse ISM J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006

  10. TLS Res. DCD TLS Hoping Planck: polarized Planck: unpolarized FIR/submm Planck Planck will be very sensitive to the shape of the dust emissivity and therefore, should allow to select a dust model Dust Temperature is an important parameter. For B-pol, we may consider measuringit (with B-pol itself, or otherwise) in order to understand dust foreground. Predictions of TLS model with dust Temperature J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006

  11. Planck sensitivity to dust polar For a resolution of 15' 0.5 mag From Pelkonen et al. J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006

  12. Planck: polarized Planck: unpolarized FIR/submm Planck Planck should allow to detect l-variations of the dust polarization(at 3-s every 1° below Av=0.5 mag). Detecting more precisely smaller variations toward more diffuse clouds may require using a polarized instrument at higher frequency like PILOT J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006

  13. PILOT vs Planck l-coverage Planck: polarized Planck: unpolarized PILOT J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006

  14. Conclusion (Dust polarization) • Today, we don't really know if dust polarization will vary with l in the sub-mm, and if yes, how ... • So, it is difficult to devise how well we will be able to subtract it from CMB channels for B-pol (and even Planck, actually ...). • WMAP has only one dust-dominated channel (90GHz). We could compare it to Archeops polarization at 353 GHz to start constraining variations. • Planck (and PILOT) should answer the question ... but actual life could be significantly more complicated than described here. • ° Other open questions: + Is there l-variations appart from dust distribution ? + Is there a contribution from spinning dust ? + Is there a contribution from HVCs ? + Is there a contribution from ZL ? J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006

  15. The END • PILOT will attempt at measuring the linear polarization from dust emission in our Galaxy to very high accuracy levels at high frequencies • The goal is to understand the physics of dust polarization, to ultimately help with component separation for B-pol • PILOT is a test-bed for the use of compact multiplexed bolometer arrays for polarization measurements • PILOT is funded by CNES. Detailed definition is ending and realization of the instrument is starting. • First flight expected in end-2008 (Kiruna) PILOT PILOT is the pilot fish Future CMB-pol mission ? http://pilot.cesr.fr J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006

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