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CFHT Fabry-Perot 2D spectroscopy in Hα of the ejected Wolf-Rayet ring nebula M1-67: universal multifractal analysis and turbulent status

Published online by Cambridge University Press:  26 May 2016

Yves Grosdidier
Affiliation:
Ernest Rutherford Physics Building, McGill University, 3600 rue University, Montréal, QC H3A 2T8, Canada
Anthony F.J. Moffat
Affiliation:
Département de physique, Université de Montréal, C.P. 6128, succ. Centre-Ville, Montréal, QC H3C3J7, Canada
Sébastien Blais-Ouellette
Affiliation:
Département de physique, Université de Montréal, C.P. 6128, succ. Centre-Ville, Montréal, QC H3C3J7, Canada
Gilles Joncas
Affiliation:
Département de physique, Université Laval, Sainte-Foy, QC G1K 7P4, Canada
Agnès Acker
Affiliation:
Observatoire Astronomique de Strasbourg, UMR 7550, 11 rue de l'Université, F-67000 Strasbourg, la France

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Using CFHT-sis Fabry-Perot interferograms of the Wolf-Rayet ring nebula M1-67, we present an investigation of the statistical properties of fluctuating gas motions using structure functions (SFs) traced by Hα emission-line centroid velocities. We consider the SFs 〈|Δv(r)|p〉 of order p, i.e., the spatially averaged moments of order p of the spatial velocity increments at projected spatial scale r of M1-67's velocity field: we test for (i) SF scaling, 〈|Δv(r)|p〉 ∝ rζ(p), and (ii) nonlinearity of the observed scaling exponents ζ(p)s, as expected for intermittent flows. We find that there is a clear correlation at scales 0.02-0.22 pc between the mean quadratic differences of radial velocities and distance over the surface of M1-67. The first and second order SFs are found to scale as 〈|Δv(r)|〉 ∝ r0.5 and 〈|Δv(r)|2〉 ∝ r0.9 (Grosdidier et al. 2001). The former scaling law strongly suggests that supersonic turbulence is at play in M1-67, on the other hand, the latter scaling law agrees very well with Larson-type laws for velocity turbulence. Additionally, we can discuss the nature of the turbulence in terms of Universal Multifractals (UM), a continuous-scale limit of multiplicative cascades (Schertzer & Lovejoy 1987) and derive the level of intermittency in the nebula.

Type
Part 4. Feedback from Massive Stars
Copyright
Copyright © Astronomical Society of the Pacific 2003 

References

Grosdidier, Y., Moffat, A.F.J., Blais-Quellette, S., et al. 2001, ApJ 562, 753.Google Scholar
Grosdidier, Y., et al. 2002, in: Dopita, M., Kwok, S. & Sutherland, R.S. (eds.) Planetary Nebulae: Their Evolution and Role in the Universe, Proc. IAU Symp. No. 209 (San Francisco: ASP), in press.Google Scholar
Schertzer, D., Lovejoy, S. 1987, J. Geophys. Res. 92, 9693.Google Scholar