Polarization Gradient Study of Interstellar Medium Turbulence Using the Canadian Galactic Plane Survey

被引:5
作者
Herron, C. A. [1 ]
Geisbuesch, J. [2 ,6 ]
Landecker, T. L. [1 ,2 ]
Kothes, R. [2 ]
Gaensler, B. M. [1 ,3 ]
Lewis, G. F. [1 ]
McClure-Griffiths, N. M. [4 ]
Petroff, E. [1 ,5 ]
机构
[1] Univ Sydney, Sch Phys, Sydney Inst Astron, Sydney, NSW 2006, Australia
[2] Domin Radio Astrophys Observ, Herzberg Astron & Astrophys, Natl Res Council Canada, POB 248, Penticton, BC V2A 6J9, Canada
[3] Univ Toronto, Dunlap Inst Astron & Astrophys, 50 St George St, Toronto, ON M5S 3H4, Canada
[4] Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia
[5] ASTRON Netherlands Inst Radio Astron, Postbus 2, NL-7990 AA Dwingeloo, Netherlands
[6] Karlsruhe Inst Technol, POB 3640, D-76021 Karlsruhe, Germany
基金
澳大利亚研究理事会; 加拿大自然科学与工程研究理事会; 欧洲研究理事会;
关键词
ISM: magnetic fields; ISM: structure; magnetohydrodynamics (MHD); methods: data analysis; techniques: polarimetric; turbulence; CYGNUS X REGION; RADIO POLARIZATION; FARADAY-ROTATION; MAGNETIC-FIELDS; POWER SPECTRUM; INNER GALAXY; MILKY-WAY; 1420; MHZ; EMISSION; SKY;
D O I
10.3847/1538-4357/835/2/210
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We have investigated the magneto-ionic turbulence in the interstellar medium through spatial gradients of the complex radio polarization vector in the Canadian Galactic Plane Survey (CGPS). The CGPS data cover 1300 square degrees, over the range 53 degrees <= l <= 192 degrees, -3 degrees <= b <= 5 degrees, with an extension to b = 17 degrees.5 in the range 101 degrees <= l <= 116 degrees, and arcminute resolution at 1420 MHz. Previous studies found a correlation between the skewness and kurtosis of the polarization gradient and the Mach number of the turbulence, or assumed this correlation to deduce the Mach number of an observed turbulent region. We present polarization gradient images of the entire CGPS data set, and analyze the dependence of these images on angular resolution. The polarization gradients are filamentary, and the length of these filaments is largest toward the Galactic anti-center, with the smallest toward the inner Galaxy. This may imply that small-scale turbulence is stronger in the inner Galaxy, or that we observe more distant features at low Galactic longitudes. For every resolution studied, the skewness of the polarization gradient is influenced by the edges of bright polarization gradient regions, which are not related to the turbulence revealed by the polarization gradients. We also find that the skewness of the polarization gradient is sensitive to the size of the box used to calculate the skewness, but insensitive to Galactic longitude, implying that the skewness only probes the number and magnitude of the inhomogeneities within the box. We conclude that the skewness and kurtosis of the polarization gradient are not ideal statistics for probing natural magneto-ionic turbulence.
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页数:19
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