1999AJ....118.1461T -
Astron. J., 118, 1461-1467 (1999/October-0)
Optical and near-infrared spectroscopy of Cygnus A.
THORNTON R.J.J., STOCKTON A. and RIDGWAY S.E.
Abstract (from CDS):
We present optical and near-infrared spectroscopy of the luminous radio galaxy Cygnus A (3C 405). Optical (∼6700-9300 Å) observations were obtained of the central region, including the region where most emission lines are strongest, about 1".5 northwest of the nucleus. However, high-ionization lines ([Ar XI] and [Fe XI]), as well as an unidentified feature at ∼7608 Å, are stronger in the continuum-dominated southeast component. We detect the near-infrared Ca triplet in absorption, and we use it to obtain a new determination of the redshift and velocity dispersion of the stellar component of Cygnus A. The infrared (∼1.9-2.5 µm) spectrum of the nucleus shows emission from [Si VI], [S XI], and possibly [Si XI]. A number of molecular hydrogen transitions were also detected; their ratios favor X-ray heating from the nuclear source over other possible origins (e.g., shocks) as the most likely excitation mechanism. We see no evidence for broad-line wings on the Paα line profile, confirming that the broad-line region in Cygnus A remains heavily obscured at 2 µm.
Abstract Copyright:
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Journal keyword(s):
Galaxies: Active - galaxies: individual (Cygnus A) - Infrared Radiation
Simbad objects:
3
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