Satellite Emission Features in Two Seyfert Galaxies: New Evidence That Radio- Quiet AGN Possess Subrelativistic Winds

Abstract

HST/FOS spectra are presented for three bright Seyfert galaxies including one (PG 1351+64) which possesses blue-displaced absorption features in C IV, Si IV, N V, and Lyα (but not in Mg Il) similar to those seen at high redshift in the broad-absorption-line (BAL) QSOs. Several features of the absorptions in PG 1351+64, including variability seen in archival IUE data, confirm their similarity to the BAL clouds rather than to the "associated absorber" phenomenon which they superficially resemble. In PG 1351+64 "satellite" emission lines (called herein E1 and E2) have been detected nearly symmetrically placed at +/-4000 km s^-1^ around the Mg II emission line; this velocity is just larger than the most blue-displaced of the BALs, suggesting that these two phenomena are related. The satellite line luminosity, L(E1)~(3 x 10^41^ erg s^- 1^)h_75_^-2^, requires a cloud emission measure n_e_^2^ V_c_~(1 x 10^64^ cm^-3^) h_75_^-2^ at T = 30 000 K. We believe the Mg II lines are produced by 50-90 km s^-1^ shocks driven into dense (~10^6^ cm^-3^, pre- shock) clouds by the ram pressure of a 0.1. M_sun_ yr^-1^ wind leaving the nucleus at velocity 4000 km s^-1^. The detection of satellite lines in Mg II, the detection of the blue-shifted cloud in Hα and Hβ and the nondetection of this cloud in C IV restricts the cloud shocks to velocities v_c_ <= 90 km s^-1^ and requires a cloud/wind density contrast >= 10^3^. In this model, the emitting clouds are located at distances of R_eff_ ~ 10^18-19^ cm from the nucleus and are entrained and shock- accelerated to -4000 km s^-1^. The possible detection of similar "satellite" emission features in the non-BAL Seyfert, Ton 951, suggests that the subrelativistic wind that accelerates BAL clouds is a physical feature of many radio-quiet AGN.