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Optical images in true colours of the cirrus field obtained with MegaCam on the CFHT. Image credits: MATLAS collaboration, Pierre-Alain Duc.
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Combined power spectrum : black is Planck radiance, red is WISE and blue is MegaCam. The units of the y axis are arbitrary; each power spectrum was scaled in order to match the others. For each power spectrum, we show data points corresponding to scales larger than the beam and where the power is above the noise component. The data points shown here are noise subtracted and divided by the beam function. The best fit gives P(k) ~ k^(2.9±0.1). Figure from Miville-Deschênes et al. 2016.
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One advantage of the high angular resolution provided by the CFHT data is to eventually reach the angular scale at which turbulent energy dissipates. Understanding the exact process by which kinetic energy is dissipated and heats gas is essential. It is key in the formation of dense structures that lead to the formation of stars. For instance, recent studies based on Herschel observations of molecular clouds have revealed the presence of filaments with widths of 0.1 pc that seem constant whatever their mass. This observational fact has been attributed to the energy dissipation process, namely ambipolar diffusion (friction between neutrals and ions). The present study shows that the dissipation scale in the interstellar medium is smaller than 0.01 pc which brings important constraints on the exact process resposible for this dissipation.
These results emphasize the fact that scattered light from cirrus, an important source of pollution for deep imaging destined to mapping diffuse structures around massive galaxies, is carrying potentially precious information about the nature of the physical processes involved in the evolution of matter in our own galaxy.