Optical surface features and morphologic properties of the Orion Nebula |
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| Authors: | Karl Wurm Mario Perinotto |
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| Institution: | (1) Asiago Astrophysical Observatory, Italy |
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| Abstract: | In the field partsH, K, L andM of the Orion Nebula, indicated in Figure 2, no obvious differences do appear in the monochromatic photographs obtained in H +Nii], Oii], the visual continuum and the range of the Balmer continuum. A different situation we meet in the rest of the field, where one observes two types of featuresA andB, distinguished in Figure 1 by solid and dashed bordering lines respectively. Relative to the conditions in the H+Nii] pictures, the typeA areas gain in intensity in the photographs taken in the visual continuum. the emission in the forbidden Oii] lines at  3727 Å is correlated with H+Nii], the emission in the range of the Balmer continuum with the visual continuum. According to these properties theA-areas must have a particularly high percentage of scattered star light.Most of the areas with identical monochromatic features show a high deficiency of cluster stars correlated with a low surface brightnesss and a reduced gas density. This is explained by an opaqueness of the emission strata in the direction in the line of sight and a position of the same nearer to the observer than the extension of the cluster. There appear surface structures at large distances from the Trapezium which show a correlation between the intensity of scattered star light and the intensity of the emission of the higher ions (Oiii], Neiii]). This observation is considered as a proof that  canals through the nebular cloud complex allow in some directions the exciting radiation to reach large distances from the star without having suffered an appreciable absorption or scattering. |
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