Planck results challenge dust models and alignment mechanisms ========= Planck 2018 Results XII & others ========= Vincent Guillet (IAS Orsay, LUPM Montpellier) on behalf the Planck collaboration Collaborators: F. Levrier (ENS/LRA), F. Boulanger (ENS/LRA) P. Martin (CITA), L. Fanciullo (ASIAA), A. Jones (IAS), M.-A. Miville-Deschênes (CEA/SAp), L. Verstraete (IAS), G. Green (Stanford University), N. Ysard (IAS), M. Alves (Radboud University) Cosmic Dust & Magnetism - 30 Oct. 2018 1 V. Guillet - Planck results challenge dust models and alignment mechanisms
OUTLINE 1. Dust polarization at high Galactic latitude 2. Magnetic field versus grain alignment è Origin for the variations of the polarization fraction p ? 3. A dust model for translucent lines of sight 4. New constraints for high latitude diffuse dust è Combining Planck and starlight data at high Galactic latitude 5. Conclusions & questions Cosmic Dust & Magnetism - 30 Oct. 2018 2 V. Guillet - Planck results challenge dust models and alignment mechanisms
OUTLINE 1. Dust polarization at high Galactic latitude 2. Magnetic field versus grain alignment è Origin for the variations of the polarization fraction p ? 3. A dust model for translucent lines of sight 4. New constraints for high latitude diffuse dust è Combining Planck and starlight data at high Galactic latitude 5. Conclusions & questions Cosmic Dust & Magnetism - 30 Oct. 2018 3 V. Guillet - Planck results challenge dust models and alignment mechanisms
Polarization fraction as seen from the Galactic poles What is new since Planck 2015 results ? Polarization at high latitude and low N H (< 10 20 cm -2 ) SOUTHERN HEMISPHERE NORTHERN HEMISPHERE p = P/I 353 GHz 80 arcmin 0.0 20.0 p [%] Cosmic Dust & Magnetism - 30 Oct. 2018 4 V. Guillet - Planck results challenge dust models and alignment mechanisms
Planck full-sky maps at 353 GHz (850 µm) Planck full-sky maps with reduced systematics PR3-2018: http://pla.esac.esa.int/pla/ Q 353 Q 2 + U 2 P = Polarized intensity P 353 is biased by noise Smoothing (Planck XIX 2015) Debiasing using full covariance U 353 maps (Plaszczynski +2014) GNILC Intensity map Polarization fraction p = P 353 /I 353 Generalized Internal Linear Combination (Remazeilles+2011) I 353 CIB : key issue at high latitude Fluctuations removed by GNILC Galactic offset : 0.0181 MJy sr −1 ± 0.0115 MJy sr −1 Cosmic Dust & Magnetism - 30 Oct. 2018 5 V. Guillet - Planck results challenge dust models and alignment mechanisms
Maximal value for the polarization fraction p = P / I at 353 GHz At FWHM = 80 arcmin of resolution, we have ~ 2.10 5 pixels Low Offset Fidicuial Offset High offset + 3.5 % p max = 22.4 − 1.4 p / E(B-V) < 9% (Serkowski+1975) ? (99.9 th percentile) Cosmic Dust & Magnetism - 30 Oct. 2018 6 V. Guillet - Planck results challenge dust models and alignment mechanisms
Systematic drop of the polarization fraction p with N H Planck 2015 results 95 th percentile | b | > 5° A drop long observed and Intensity offsets discussed in starlight polarization (optical, NIR): • Hiltner (1956) Running • Serkowski+1975 mean • Vrba+1981 • Jones (1989) • Goodman+1992 • Whittet+1994 • Gerakines+1995 • Fosalba+2002 • Andersson+2007 • Whittet+2008 • Alves+2014 … • (derived from τ 353 ) Cosmic Dust & Magnetism - 30 Oct. 2018 7 V. Guillet - Planck results challenge dust models and alignment mechanisms
OUTLINE 1. Dust polarization at high Galactic latitude 2. Magnetic field versus grain alignment è Origin for the variations of the polarization fraction p ? 3. A dust model for translucent lines of sight 4. New constraints for high latitude diffuse dust è Combining Planck and starlight data at high Galactic latitude 5. Conclusions & questions Cosmic Dust & Magnetism - 30 Oct. 2018 8 V. Guillet - Planck results challenge dust models and alignment mechanisms
How to disentangle between alignment and depolarization ? In emission (Rayleigh approximation when a << λ ) : Magnetic field p = p max RF cos 2 γ inclination (Planck Int. Results 2015 XX) Magnetic field disorder (line of sight, beam) Grain shape Grain alignment & composition (Rayleigh reduction factor) Polarization fraction in Ophiuchus Angle structure function S (Planck Int. Results 2015 XIX) (Planck Int. Results 2015 XIX) Cosmic Dust & Magnetism - 30 Oct. 2018 9 V. Guillet - Planck results challenge dust models and alignment mechanisms
Anticorrelation of S with p also observed at high latitude SOUTHERN HEMISPHERE NORTHERN HEMISPHERE 160 arcmin Cosmic Dust & Magnetism - 30 Oct. 2018 10 V. Guillet - Planck results challenge dust models and alignment mechanisms
Inverse correlation of S with p Heiles (1996) Planck 2018 Results. XII Hatano+2013 160 arcmin Planck Int. Results 2015 XIX BlastPOL : Fissel+2016 S and p are anticorrelated Planck 2018 Results XII p = C te S × p <S x p> shows less variations with the column density • the latitude • the longitude • than < p> alone. Cosmic Dust & Magnetism - 30 Oct. 2018 11 V. Guillet - Planck results challenge dust models and alignment mechanisms
Recommend
More recommend
