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Date and Time of the Query: 2019-06-19 T23:23:01 PDT
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2013NewA...19...89D Probing interstellar turbulence in spiral galaxies using H I power spectrum analysis Dutta, Prasun; Begum, Ayesha; Bharadwaj, Somnath; Chengalur, Jayaram N. Abstract. We estimate the H I intensity fluctuation power spectrum for a sample of 18 spiral galaxies chosen from THINGS. Our analysis spans a large range of length-scales from ~300 pc to ~16 kpc across the entire galaxy sample. We find that the power spectrum of each galaxy can be well fitted by a power law P_(U)=AU^{alpha}^, with an index {alpha} that varies from galaxy to galaxy. For some of the galaxies the scale-invariant power-law power spectrum extends to length-scales that are comparable to the size of the galaxy's disk. The distribution of {alpha} is strongly peaked with 50% of the values in the range {alpha}=-1.9 to 1.5, and a mean and standard deviation of -1.3 and 0.5 respectively. We find no significant correlation between {alpha} and the star formation rate, dynamical mass, H I mass or velocity dispersion of the galaxies.Several earlier studies that have measured the power spectrum within our galaxy on length-scales that are considerably smaller than 500 pc have found a power-law power spectrum with {alpha} in the range ~-2.8 to -2.5. We propose a picture where we interpret the values in the range ~-2.8 to -2.5 as arising from three dimensional (3D) turbulence in the interstellar medium (ISM) on length-scales smaller than the galaxy's scale-height, and we interpret the values in the range ~-1.9 to -1.5 measured in this paper as arising from two-dimensional ISM turbulence in the plane of the galaxy's disk. It however still remains a difficulty to explain the small galaxy to galaxy variations in the values of {alpha} measured here.
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