Astronomy and Astrophysics – Astronomy
Scientific paper
Oct 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994aj....108.1178s&link_type=abstract
The Astronomical Journal, vol. 108, no. 4, p. 1178-1185
Astronomy and Astrophysics
Astronomy
9
Absorption Spectra, Active Galactic Nuclei, Astronomical Models, Emission Spectra, Line Spectra, Quasars, Seyfert Galaxies, Stellar Luminosity, Stellar Spectra, Ultraviolet Astronomy, Ultraviolet Spectra, Astronomical Spectroscopy, Carbon, Hubble Space Telescope, Lyman Alpha Radiation, Nitrogen, Silicon, Spectrographs, Ultraviolet Spectroscopy
Scientific paper
Hubble Space Telescope (HST) Faint Object Spectrograph (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 Ly-alpha (but not in Mg II) similar to those seen at high redshift in the broad-absorption-line (BAL) quasi-stellar objects (QSOs). Several features of the absorptions in PG 1351+64, including variability seen in archival International Ultraviolet Explorer (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 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) approximately = (3 x 1041 erg/s)/sq. h75, requires a cloud emission measure ne2Vc approximately = (1 x 1064/cc)/sq. h75 at T approximately = 30,000 K. We believe the Mg II lines are produced by 50-90 km/s shocks driven into dense (approximately 106/cc, pre-shock) clouds by the ram pressure of a 0.1 solar mass/yr wind leaving the nucleus at velocity 4000 km/s. The detection of satellite lines in Mg II, the detection of the blue-shifted cloud in H-alpha and H-beta and the nondetection of this cloud in C IV restricts the cloud shocks to velocities vc less than or = 90 km/s and requires a cloud/wind density contrast greater than or = 103. In this model, the emitting clouds are located at distances of Reff approximately = 1018-19 cm from the nucleus and are entrained and shock-accelerated to approximately 4000 km/s. 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 active galactic nuclei (AGN).
Granados Arno F.
Sachs Elise R.
Shull Michael
Stocke John T.
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