2001/05/17 by A. B. Peck, G. B. Taylor
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #astro-ph
paper · pdf · doi:10.1086/321699
13 pages, 2 b/w figures, 2 color figures, figure quality degraded in the interests of space. To appear in ApJ Letters
arxiv created 2001/05/17 · openalex publication_date 2001/06/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
A number of extragalactic radio sources that exhibit symmetric jets on parsec scales have now been found to have neutral hydrogen absorption at or near the systemic velocities of their host galaxies. Understanding the spatial distribution and kinematics of the H I detected toward the central parsecs of these sources provides an important test of unified schemes for active galactic nuclei. We present results of Global VLBI Network observations of the redshifted 21 cm H I line toward the compact symmetric object 1946+708 ( z = 0.101). We find significant structure in the gas on parsec scales. The peak column density of the H I ( N ~ 3 × 10 23 cm -2 [ T s /(8000 K)]) occurs near the center of activity of the source, as does the highest velocity dispersion (FWHM ≃ 350-400 km s -1 ). There is also good evidence for a torus of ionized gas with column density 7 × 10 22 cm -2 . The jets in 1946+708 exhibit bidirectional motion measurable on timescales of a few years. The resulting unique information about the geometry of the continuum source greatly assists in the interpretation of the gas distribution, which is strongly suggestive of a circumnuclear torus of neutral atomic and ionized material with one or more additional compact clumps of gas along the line of sight to the approaching jet.