The role of the magnetic field in the formation of structure in molecular clouds

Transcription

1 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

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3 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

4 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.

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

6 Observations Simulations Relative orientation Magnetic field Turbulence Gravity

7 Column density and magnetic field orientation Ophiuchus Cepheus Aquila Rift Taurus Lupus Chamaeleon-Musca IC5146 Orion 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.

8 Lupus Ophiuchus

9 Relative Orientations Soler et al, 2013

10 Soler et al, 2013

11 Soler et al, 2013

12 Soler et al, 2013

13 Histogram of Relative Orientations Weak magnetic field Strong magnetic field Simulations of MHD turbulence by P. Hennebelle HRO: Soler et al, 2013

14 Weak magnetic field Histogram of Strong magnetic field Relative Orientations

15 3D Weak field β = Equipartition β = 1.0 Strong field β = 0.1!! Soler et al, 2013

16 2D Weak field β = Equipartition β = 1.0 Strong field β = 0.1!! N Soler et al, 2013

17 Histogram of Relative Orientations Taurus region! NH from dust optical depth B from Planck 353 GHz pol. 16 deg (40 d=140 pc) 10 FWHM (0.4 d=140 pc) Planck intermediate results. XXXV

18 Histogram of Relative Orientations Taurus region! Perpendicular Parallel Planck intermediate results. XXXV

19 Planck intermediate results. XXXV

20 Histogram of Relative Orientations Planck intermediate results. XXXV

21 Histogram of Relative Orientations Planck intermediate results. XXXV

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23 Histogram of Relative Orientations All sky after selection Planck intermediate results. XXXII arxiv: A&A accepted

24 Histogram of Relative Orientations Weak field! Equipartition! Strong field! MAGNETIC EB EB Ek E Ek GRAVITATIONAL KINETIC Planck intermediate results. XXXV

25 Magnetic fields in molecular cloud formation What have we learned? Magnetic field at least in equipartition with turbulence. Magnetic field comparable to gravity? DCF EB Eg? MAGNETIC EB HRO EB Ek B Eg Ek GRAVITATIONAL KINETIC Planck intermediate results. XXXV Eg Ek Virialized structure

26 Magnetic fields in molecular cloud formation Davis-Chandrasekhar-Fermi MAGNETIC DCF EB HRO Transverse Alfvén waves Magnetic field frozen into the gas.? EB Ek Eg Ek Davis, L., 1951 Chandrasekhar, S. & Fermi, E., 1953 Hildebrand, R. et al., 2009 Houde, M., 2009 GRAVITATIONAL Eg Ek Virialized structure KINETIC Planck intermediate results. XXXV

27 Magnetic fields and cloud formation Density structures and B stretched in the same direction. Flows occur mainly along B. EB Ek! Planck intermediate results. XXXII Hennebelle, P., 2013 Banerjee, R., 2009 Matthaeus, W. et al, 2008 EB > Ek Inutsuka, S., 2015 Nakamura F. & Li, Z., 2008

28 @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 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: A&A accepted

29 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 How is the dust grain alignment efficiency in different regions of a molecular cloud? Soler et al, 2015 in preparation

30 Zoom in Vela C region Planck 850 micron at 10 BLASTPol 500 micron at 2 IN PREPARATION Fissel, L. and BLASTPol collaboration, 2015 in preparation Soler, J.D. and BLASTPol collaboration, 2015 in preparation

31 Thanks! Visit