Astronomy and Astrophysics – Astrophysics
Scientific paper
2003-06-26
Astron.Astrophys.411:109-122,2003
Astronomy and Astrophysics
Astrophysics
15 pages, 15 figures, accepted for publication in A&A. Version with higher-resolution color figures can be found at http://w
Scientific paper
10.1051/0004-6361:20031297
We present a power spectrum analysis of interferometric 21 cm observations of the Ursa Major high-latitude cirrus, obtained with the Dominion Radio Astrophysical Observatory (DRAO) of Penticton (Canada). These high-resolution data reveal the intricate structure of the diffuse Galactic HI, at angular scales from 1 arcminute to 3 degrees. A filtering method based on a wavelet decomposition was used to enhance the signal-to-noise ratio of the data. The power spectra of the integrated emission and of the centroid velocity fields were used to deduce the three-dimensional (3D) spectral index of the density and velocity fields of the HI cirrus. The spectral index is similar for the 3D density and velocity fields with a value of -3.6\pm0.2. Using the Leiden/Dwingeloo observations, this analysis was extended to the whole North Celestial Loop (which includes the Ursa Major cirrus), showing that the scaling laws prevail from 0.1 to 25 pc. The centroid velocity and integrated emission fields show moderate correlation, with a maximum cross-correlation value of 0.44.
Boulanger Francois
Falgarone Edith
Joncas Gilles
Miville-Deschênes Marc-Antoine
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