Scattered Nuclear Continuum and Broad H\alpha in Cygnus A

Session 51 - Active Galactic Nuclei & Quasars.
Oral session, Thursday, June 12
North Main Hall A,

[51.07] Scattered Nuclear Continuum and Broad H\alpha in Cygnus A

H. D. Tran (UCO/Lick Obs.), P. M. Ogle, M. H. Cohen (Caltech), J. S. Miller (UCO/Lick Obs.), R. A. E. Fosbury (ST-ECF/ESO), R. W. Goodrich (Keck Obs.)

We have discovered scattered broad Balmer emission lines in the spectrum of Cygnus A, using the Keck II telescope. Broad H\alpha appears in polarized flux from components on either side of the nucleus, and to a lesser extent in the nucleus. The full-width at half-maximum of broad H\alpha is 26,000 km s^-1, comparable to the widest emission lines seen in broad-line radio galaxies. Scattered AGN light provides a significant contribution to the total flux at 3800 Årest) of the western component, where the polarization rises to 16%. The spatially integrated flux of Cygnus A at 5500 Åcan be decomposed into an elliptical galaxy fraction (F_g=0.70), a highly polarized blue component (FC1=0.15), a less polarized red component (FC=0.09), and a contribution from the nebular continuum (0.06). Imaging polarimetry shows a double fan of polarization vectors with circular symmetry which corresponds to the ionization cone seen in HST images. Our results are consistent with scattering of light from a hidden quasar of modest luminosity by an extended, dusty narrow-line region.

Program listing for Thursday