Candidates of Hα Emitting Regions in the Magellanic Stream IV Cloud
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From H alpha narrowband observations, we identified three H alpha emitting regions in the direction of Magellanic Stream IV (MS IV). They consist of three parallel filaments of 2 arcmin width and 6-30 arcmin length at 12 arcmin intervals. Their mean surface brightness (SB) is similar to 2 x 10(-18) erg s(-1) cm(-2) arcsec(-2). Because of their low SB, the regions were not detected in previous Ha surveys. In the HI map, the position of the filaments overlap MS, suggesting that they are parts of the MS, but there also exists a local HI structure. If the filaments are associated with the MS, the sizes are 30 pc x 100-500 pc. The filaments lie at the leading edge of a downstream cloud, which supports shock heating and its propagation (shock cascade) model for the ionizing source. If they are local objects, on the other hand, Fossil Stromgren Trails of more than two stars is a possible interpretation, and the sizes would be 0.1 pc x 0.3-1.5 pc at 180 pc distance. The positional information of the H alpha filaments presented in this Letter enables future spectroscopic observations to clarify their nature.
- Astrophysical Journal Letters
Astrophysical Journal Letters 749(1), L2, 2012
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