Anomalous Motion of Ionized Gas in the Sickle (G0.18−0.04) near the Galactic Center

We present VLA measurements of H92alpha radio recombination line emissionfrom an unusual HII region G0.18--0.04, the ``Sickle'', with spatial andspectral resolutions of 27" times 24".9 and 14 km/s, respectively. Theseobservations detected two new kinematic components of ionized gas whosevelocities differ greatly from the +25 km/s molecular cloud surrounding theSickle. One component is highly red-shifted with peak velocity of about +150km/s and the other is a blue-shifted velocity feature peaking near -35 km/s.Neither of these high-velocity features have molecular counterparts. Theblue-shifted feature is forbidden in the sense of Galactic rotation andcoincides with the prominent nonthermal filaments crossing the Sickle, thussuggesting that they are physically associated with each other. The resultspresented here are interpreted in terms of ionized gas being accelerated awayfrom the surface of the cloud associated with the Sickle region, either by themagnetic field associated with the nonthermal filaments or by the stellar windsfrom the hot helium stars near G0.18--0.04.Comment: 8 pages, LaTeX/aaspp4.sty, 3 ps figs, 1 gif (fig 4), to appear in ApJ Let