The galaxy continuum in the spectrum of Cygnus A

It is pointed out that high-dispersion, long-exposure spectral scans have recently been obtained in an attempt to detect in the nucleus the Mg I b 5175-A absorption feature, which is the best signal of a galaxy in this situation. Even though difficult to see because it is between fairly strong forbidden N I 5199-A and weak forbidden Fe VII 5159-A emission lines, the Mg I feature is definitely present in the nucleus of Cyg A. Its equivalent width is about 2.3 A. If the underlying galaxy possesses an absorption-line spectrum similar to a giant elliptical, this would correspond to about 0.4 of the optical continuum near 5175 A coming from the galaxy, and 0.6 from the featureless continuum of the active nucleus. Whereas late-type spirals have weaker Mg I b absorption, other features, such as Fe II 5269 A, then have a comparable strength. These features are not seen in Cyg A nucleus scans. Measurements of a few additional emission-line strengths in the near infrared spectrum of Cyg A are presented.