Martin HoudeWestern Science

Characterizing Magnetized Turbulence in Molecular Clouds and Galaxies

In recent publications (Hildebrand et al. 2009, ApJ, 696, 567; Houde et al. 2009, ApJ, 706, 1504;Houde et al. 2011, ApJ, 733, 109) my collaborators and I have introduced a new technique for the observational characterization of magnetized turbulence in molecular clouds. Information about the turbulent content of magnetic fields is contained within, and can be obtained from, polarization data measurements (e.g., maps of polarization from dust continuum emission). For example, in Houde et al. (2009) we showed how to determine the turbulence correlation length in molecular clouds, which is, in fact, a measure of the width of the magnetized turbulent power spectrum. In Houde et al. (2011) we recently pushed our analysis even further by using high-resolution SMA interferometry polarization maps to directly determine the magnetized turbulent power spectrum of three star-forming regions. We were successful in modelling the inertial range with a Kolmogorov-like power law and determining the high spatial frequency cut-off presumably due to turbulent ambipolar diffusion. Finally, we successfully applied this technique to VLA/Effelsberg polarized synchrotron data of M51 (Houde et al. 2013, ApJ, 766, 49) to, among other things, measure the anisotropy of the magnetized turbulence in this galaxy.


Polarized Flux for M51

Fig. 3. Polarized flux at λ6.2cm for M51. There are three regions that can be independently used (or combined) for a dispersion analysis: the spiral arms in the northeast and southwest, and the center of the galaxy. These regions are contained within the corresponding three red parallelograms in the figure. The map is centred at right ascension (J2000) = 11h29m52.4s, declination (J2000) = 47°11′43.5″, and the contours are drawn at 20%-80% (10% increments) of the peak polarized flux density (173 μJy beam-1).