Faint HI 21-cm Emission Line Wings at Forbidden-Velocities

Abstract

We present the results of a search for faint HI 21-cm emission line wings at velocities forbidden by Galactic rotation in the Galactic plane using the Leiden/Dwingeloo HI Survey data and the HI Southern Galactic Plane Survey data. These ``forbidden-velocity wings (FVWs)'' appear as protruding excessive emission in comparison with their surroundings in limited (< 2 deg) spatial regions over velocity extent more than ~20 km/s in large-scale (l-v) diagrams. Their high-velocities imply that there should be some dynamical phenomena associated. We have identified 87 FVWs. We present their catalog, and discuss their distribution and statistical properties. We found that 85% of FVWs are not coincident with known supernova remnants (SNRs), galaxies, or high-velocity clouds. Their natures are currently unknown. We suspect that many of them are fast-moving HI shells and filaments associated with the oldest SNRs that are essentially invisible except via their HI line emission. We discuss other possible origins.

arXiv comment41 pages, 14 figures, to be published in apjs

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Cited by in corpus (9)

• Gaseous Galaxy Halos
• The H.E.S.S. Galactic plane survey
• GASKAP -- The Galactic ASKAP Survey
• Radiative Supernova Remnants and Supernova Feedback
• An Old Supernova Remnant within an HII Complex at l {\approx} 173{\circ}: FVW 172.8+1.5
• VLBI search for the radio counterpart of HESS J1943+213
• A High-Velocity Cloud Impact Forming a Supershell in the Milky Way
• Broad-velocity-width Molecular Features in the Galactic Plane
• Cosmic Rays and Non-thermal Emission Induced by Accretion of Cool Gas onto the Galactic Disk