Ultraviolet Broad Absorption Features and the Spectral Energy Distribution of the Quasar PG 1351+64
Abstract
We present a moderate-resolution (~20 km s-1) spectrum of the mini-broad absorption line quasar (QSO) PG 1351+64 between 915 and 1180 Å, obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE). Additional low-resolution spectra at longer wavelengths were also obtained with the Hubble Space Telescope (HST) and ground-based telescopes. Broad absorption is present on the blue wings of C III λ977, Lyβ, O VI λλ1032, 1038, Lyα, N V λλ1238, 1242, Si IV λλ1393, 1402, and C IV λλ1548, 1550. The absorption profile can be fitted with five components at velocities of ~-780, -1049, -1629, -1833, and -3054 km s-1 with respect to the emission-line redshift of z=0.088. All the absorption components cover a large fraction of the continuum source, as well as the broad-line region. The O VI emission feature is very weak, and the O VI/Lyα flux ratio is 0.08, one of the lowest among low-redshift active galaxies and QSOs. The UV continuum shows a significant change in slope near 1050 Å in the rest frame. The steeper continuum shortward of the Lyman limit extrapolates well to the observed weak X-ray flux level. The absorbers' properties are similar to those of high-redshift broad absorption line QSOs. The derived total column density of the UV absorbers is on the order of 1021 cm-2, unlikely to produce significant opacity above 1 keV in the X-ray. Unless there is a separate, high-ionization X-ray absorber, the QSO's weak X-ray flux may be intrinsic. The ionization level of the absorbing components is comparable to that anticipated in the broad-line region; therefore, the absorbers may be related to broad-line clouds along the line of sight. Based on observations made for the Guaranteed Time Team by the NASA-CNES-CSA FUSE mission, operated by the Johns Hopkins University under NASA contract NAS 5-32985, and observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities of Research in Astronomy, Inc., under NASA contract NAS 5-26555.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2001
- DOI:
- 10.1086/323437
- arXiv:
- arXiv:astro-ph/0107536
- Bibcode:
- 2001ApJ...562..152Z
- Keywords:
-
- Galaxies: Active;
- Galaxies: Quasars: Absorption Lines;
- quasars: individual (PG 1351+64);
- Ultraviolet: Galaxies;
- Astrophysics
- E-Print:
- 23 pages, Latex, 5 figures