Faint HI 21-cm Emission Line Wings at Forbidden-Velocities - AstrophysicsReport as inadecuate

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Abstract: We present the results of a search for faint HI 21-cm emission line wings atvelocities forbidden by Galactic rotation in the Galactic plane using theLeiden-Dwingeloo HI Survey data and the HI Southern Galactic Plane Survey data.These ``forbidden-velocity wings (FVWs)- appear as protruding excessiveemission in comparison with their surroundings in limited (< 2 deg) spatialregions over velocity extent more than ~20 km-s in large-scale (l-v) diagrams.Their high-velocities imply that there should be some dynamical phenomenaassociated. We have identified 87 FVWs. We present their catalog, and discusstheir distribution and statistical properties. We found that 85% of FVWs arenot coincident with known supernova remnants (SNRs), galaxies, or high-velocityclouds. Their natures are currently unknown. We suspect that many of them arefast-moving HI shells and filaments associated with the oldest SNRs that areessentially invisible except via their HI line emission. We discuss otherpossible origins.

Author: Ji-hyun Kang, Bon-Chul Koo

Source: https://arxiv.org/

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