Astronomy and Astrophysics – Astronomy
Scientific paper
Nov 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995apj...454..316m&link_type=abstract
Astrophysical Journal v.454, p.316
Astronomy and Astrophysics
Astronomy
13
Turbulence
Scientific paper
A total of 12,695 Hα radial velocities were measured across the H II region Sh 170 using a Fabry-Perot camera. The mean VLSR of the ionized gas is - 50.10±0.08 km s-1 with a velocity dispersion of 8.70±0.05 km s-1. Sh 170 has a blueshift of 6.4 km s-1 with respect to the associated molecular cloud. The nebula is density bounded on all visible sides, indicating that the H II region is seen in front of the molecular cloud. The velocity field can be explained as an expansion of the ionized gas away from the molecular cloud toward the observer. A north-south velocity gradient of 1.4 km s-1 pc is also observed. The locus of the less negative velocity (VLSR ≍ -45 km s-1) coincides with the molecular cloud's position. Several kinematical and morphological aspects of Sh 170 are in good agreement with the "Champagne" phase model. Sh 170 has a ˜2 pc cavity devoid of ionized gas approximately centered on the ionizing star which can be explained by the action of a stellar wind. The large number of velocity measurements allowed a systematic analysis of velocity fluctuations in Sh 170. The relation between centroid velocity dispersion σc and scale l derived. The two-point autocorrelation (C) and structure (S) functions were used; these are reliable tools for the investigation of the statistical properties of fluctuating gas motions. It was found that velocity correlation occurs at scales smaller than 0.7 pc in Sh 170. The e-folding length of the autocorrelation function (the correlation length) is 0.03±0.02 pc, and a power-law relation between S and scale was obtained: S(τ) ∝ τ0.8±0.1. An interpretation of these results in terms of turbulence is presented.
Durand Daniel
Joncas Gilles
Miville-Deschênes Marc-Antoine
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