The role of the magnetic field in the formation of structure in molecular clouds Juan Diego Soler Institute d’Astrophysique Spatiale (France) on behalf of the Planck collaboration IAU General Assembly. FM5: The Legacy of Planck. August 11-13, 2015

Dust polarized emission and the magnetic field

Polarized fraction Hall, 1949 Hiltner, 1949 Davis & Greenstein, 1951 Hoang & Lazarian, 2007

Planck 2015 results. I. Overview of products and results Column density and magnetic field orientation

• NH derived from dust optical depth - Planck Collaboration XI. • B⊥ estimated from Planck 353 GHz polarization. • Texture obtained with line integral convolution - Cabral & Leedom 1993. Magnetic field and polarization statistics

• Angle dispersion Planck intermediate results. XIX • Polarized fraction Planck intermediate results. XX • Power spectrum Planck intermediate results. XXX • Geometric modelling 353 GHz Planck intermediate results. XXXIII Polarization angle Planck intermediate results. XXXIV • Relative orientation Planck intermediate results. XXXII Planck intermediate results. XXXV • Relation to E- and B-modes Planck intermediate results. XXXVIII

http://planckandthemagneticfield.info 353 GHz Polarized flux Observations Simulations

Relative orientation

• Magnetic field • Turbulence • Gravity Column density and magnetic field orientation

Ophiuchus Cepheus Aquila Rift Lupus Taurus Chamaeleon-Musca Orion IC5146 Perseus CrA

• NH derived from dust optical depth - Planck Collaboration XI. • B⊥ estimated from Planck 353 GHz polarization. • Texture obtained with line integral convolution - Cabral & Leedom 1993. Lupus

Ophiuchus Relative Orientations

Soler et al, 2013 Soler et al, 2013 Soler et al, 2013 Soler et al, 2013 Histogram of Relative Orientations

Weak magnetic field Strong magnetic field

Simulations of MHD turbulence by P. Hennebelle HRO: Soler et al, 2013 HistogramWeak magnetic field of Strong magnetic field Relative Orientations Weak field β = 100.0 3D Equipartition β = 1.0 Strong field β = 0.1 ! !

Soler et al, 2013 Weak field β = 100.0 2D Equipartition β = 1.0 Strong field β = 0.1 ! !

N

-90.0 0.0 90.0 Soler et al, 2013 Histogram of Relative Orientations Taurus region! • NH from dust optical depth • B⊥ from Planck 353 GHz pol.

16 deg (40 pc @ d=140 pc)

10’ FWHM (0.4 pc @ d=140 pc) Planck intermediate results. XXXV Histogram of Relative Orientations Taurus region! • Perpendicular • Parallel

Planck intermediate results. XXXV Planck intermediate results. XXXV Histogram of Relative Orientations

Planck intermediate results. XXXV Histogram of Relative Orientations

Planck intermediate results. XXXV

Histogram of Relative Orientations

All sky after selection

Planck intermediate results. XXXII arXiv:1411.2271 A&A accepted Histogram of Relative Orientations

Weak field! Equipartition! Strong field! MAGNETIC

EB

EB ≥ Ek

E Ek

GRAVITATIONAL KINETIC

Planck intermediate results. XXXV Magnetic fields in molecular cloud formation

What have we learned? MAGNETIC • Magnetic field at least in equipartition with turbulence. DCF EB HRO • Magnetic field comparable to gravity? EB ≥ Eg? EB ≥ Ek

B⊥

Eg Ek

GRAVITATIONAL KINETIC

Eg ≈ Ek Virialized structure Planck intermediate results. XXXV Magnetic fields in molecular cloud formation

Davis-Chandrasekhar-Fermi MAGNETIC

DCF EB HRO

? EB ≥ Ek • Transverse Alfvén waves • Magnetic field frozen into the gas.

Eg Ek

Davis, L., 1951 GRAVITATIONAL KINETIC Chandrasekhar, S. & Fermi, E., 1953 Eg ≈ Ek Hildebrand, R. et al., 2009 Houde, M., 2009 Virialized structure

Planck intermediate results. XXXV Magnetic fields and cloud formation

• Density structures and B • Flows occur mainly along B. stretched in the same direction.

EB ≤ Ek EB > Ek ! Planck intermediate results. XXXII Inutsuka, S., 2015 Hennebelle, P., 2013 Nakamura F. & Li, Z., 2008 Banerjee, R., 2009 Matthaeus, W. et al, 2008 @Planck polarization observations provide an unprecedented data set for the study of the magnetic field in molecular clouds #PlanckRocks

In 10 nearby MCs, high-NH structures mostly perpendicular to the field. May have formed by #ConvergingFlows or #GravitationalCollapse along the field

Comparison with sims of @MHDturbulence shows that this trend is only possible if the turbulence is trans-Alfvénic or sub- Alfvénic #MagneticFieldMatters

Planck intermediate results. XXXV Corresponding author: Juan D. Soler (IAS, France) arXiv:1502.04123 A&A accepted Open questions

Are we mostly looking at the integrated magnetic field morphology or the effect of dust grain alignment? #OneBigQuestion

What is the structure of the magnetic field on scales below the size of the Planck beam? @StarlightPolarization @BLASTPol

How is the dust grain alignment efficiency in different regions of a molecular cloud? #PolarizationSpectralIndex @BLASTPol

Soler et al, 2015 in preparation Zoom in Vela C region

IN PREPARATION Planck 850 micron BLASTPol 500 micron at 10’ at 2’

http://blastexperiment.info/

Fissel, L. and BLASTPol collaboration, 2015 in preparation Soler, J.D. and BLASTPol collaboration, 2015 in preparation Thanks!

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