H I Absorption toward the Nucleus of the Radio Galaxy PKS 2322–123 in A2597

We present sensitive, high-resolution Very Long Baseline Array observations of the central 0.″3 of PKS 2322-123 at 1.3 and 5 GHz. These observations reveal straight and symmetric jets emerging from both sides of an inverted spectrum core. The 21 cm line of atomic hydrogen is detected in absorption against the core and eastern jet with substantial opacities, but it is not seen toward the equally strong western jet. Both a narrow (110 km s-1 FWHM) and a very broad (735 km s-1 FWHM) line are seen, although the very broad line is seen only against the core. Both lines are redshifted (~220±100 km s-1) with respect to the systemic velocity. The most likely explanation for the observed H I kinematics are an atomic torus centered on the nucleus with considerable turbulence and inward streaming motions. The scale height of this torus is less than 20 pc. Although rare in flux-limited samples of compact radio sources, symmetric parsec-scale structure appears nearly ubiquitous among radio galaxies with H I absorption, probably because they are viewed more nearly edge-on through the torus.

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