Pictor A: Discovery of Strong Balmer Line Variations

Previous abstract Next abstract

Session 11 -- Luminous AGN and QSOs
Display presentation, Monday, 30, 1994, 9:20-6:30

[11.03] Pictor A: Discovery of Strong Balmer Line Variations

Paolo Marziani, Jack W. Sulentic, William C. Keel (U. Alabama), Toma\v{z} Zwitter (U. Ljubljana/U. Padova), Massimo Calvani (Padova Obs.)

We have detected strong changes in Balmer line flux and profile shape for the Broad Line Radio Galaxy Pictor A (0518--458). Comparison of spectra obtained in 1983 and 1993 reveal that strong broad line component has appeared with FWHM$\sim$400 \AA. The Balmer lines observed in 1993 are reminiscent of the rare kind (extremely broad profiles with shifted ``humps'') observed in Arp 102B, 3C390.3 and a handful of other BLRGs. Earlier observations of Pic A show much narrower and weaker broad line emission, with a centrally peaked profile and with monotonically falling line wings.

The emission line profile widths and redshift are consistent with emission from an inclined relativistic accretion disk but the relative strength of the red and blue ``humps'' are not. Considerable excess flux is observed on the red side of the profiles. It might be possible to reconcile the observations with a disk model if we assume that a ``hot spot'' co-rotating with the disk contributes to the line emission.

The rarity of Pic A--like profiles however suggests that the radial velocity spread is maximized if the orientation is such that the gas is predominantly moving along the line of sight. We show that a system of outflowing clouds (possibly a double shell) in a bi-conical geometry can reproduce the profile and the profile variations.

Monday program listing