AN H-1 ABSORPTION-LINE STUDY OF THE NONTHERMAL SHELL NEAR THE GALACTIC-CENTER, G3591-05 AND SEVERAL NEARBY UNUSUAL RADIO FEATURES

We present lambda21 cm spectral line observations, made with the C/D configuration of the VLA, of a remarkable Galactic center field containing: (1) G359.1 - 0.5, a complete nonthermal radio shell, (2) G359.2 - 0.8 (the "Mouse"), a nonthermal radio continuum feature with a cometary morphology, and (3) G359.1 - 0.2 (the "Snake"), a nonthermal object with a linear filamentary structure. Both G359.2 - 0.8 and G359.1 - 0.2 have been considered by some to be associated with the radio shell. The observations reveal that the nonthermal shell is surrounded by and is associated with atomic gas having large negative velocities (approximately -75 to -190 km s-1 ). Both the spatial distribution and velocity of the atomic gas are consistent with a previously reported complete ring of molecular material surrounding the nonthermal shell. Because of its apparent association with high velocity material, G359.1 - 0.5 is likely to be located at the distance of the Galactic center. The Snake also appears to be located near the Galactic center since both the 3 kpc arm and the -135 km s-1 feature (which is thought to be located within a few hundred parsecs of, and foreground to, the Galactic center) are clearly seen in absorption against this radio continuum source. The Mouse, however, appears to be a local object (d less-than-or-equal-to 5.5 kpc) since neither of the H I features are seen in absorption against this source. Also revealed by this observation is a strong local radio continuum source (G3 59.28 - 0.26), located about 8' from the edge of G359.1 - 0.5, with an apparent bow shock structure.