The HiiRegion Sharpless 269. I. Morphological Study of the Radial Velocity, Velocity Dispersion, and Density Fields

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Abstract
We present [S II] λλ6716.5, 6730.8 radial velocity, velocity dispersion, and density field maps of the H II region Sharpless 269 obtained using a scanning Fabry-Perot interferometer. The radial velocity field shows a clear bipolar morphology probably related to the dust/molecular lane bisecting the H II region. The mean LSR velocity (VLSR) extracted from the data is 16.45 ± 0.03 km s-1 (1 σ = 2.77 ± 0.02 km s-1), blueshifted by 1.3 km s-1 from the associated molecular cloud. The mean velocity dispersion given by subtraction of the instrumental and thermal Doppler broadenings from the FWHM of the line profiles is 16.43 ± 0.10 km s-1 (1 σ = 10.40 ± 0.07 km s-1). Line width analysis yields an east-west gradient caused by the proximity of molecular material and the outflow from a young stellar object in the western part of the nebula. The electron density field has a mainly uniform distribution but for a localized increase positionally associated with the young stellar object mentioned above. The mean density is found to be 290 ± 2 cm-3, while the maximum of the density distribution is centered near 200 cm-3. Overall, the results are in good agreement with an expansion scenario for the ionized gas except for the density field which fails to exhibit the predicted exponential drop from the exciting star to the edge of the H II region.