Power Spectrum of the Density of Cold Atomic Gas in the Galaxy toward Cassiopeia A and Cygnus A
A. A. Deshpande, K. S. Dwarakanath, W. M. Goss;
ApJ, 2000, 543, 227
ABSTRACT:We have obtained the power spectral description of the density and opacity fluctuations of the cold H I gas in the Galaxy toward Cas A and Cygnus
A.
We have employed a method of deconvolution, based on CLEAN, to estimate
the true power spectrum of optical depth of cold H I gas from the observed
distribution, taking into account the finite extent of the background source and the
incomplete sampling of optical depth over the extent of the source.
We
investigate the nature of the underlying spectrum of density fluctuations in the
cold H I gas which would be consistent with that of the observed H I optical
depth fluctuations.
These power spectra for the Perseus arm toward Cas A and
for the outer arm toward Cygnus A have a slope of 2.75+/-0.25 (3 σ
error).
The slope in the case of the Local arm toward Cygnus A is 2.5 and is
significantly shallower in comparison.
The linear scales probed here range from
0.01 to 3 pc.
We discuss the implications of our results, the
non-Kolmogorov nature of the spectrum, and the observed H I opacity variations on small
transverse scales.
KEYWORDS: ism: structure, methods: data analysis, radio lines: ism, techniques: image processing, techniques: interferometric, turbulence
PERSOKEY:statistical analysis, h_i, 21 cm, ,
CODE: deshpande2000