Astronomy and Astrophysics – Astronomy
Scientific paper
Oct 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993apj...416..536s&link_type=abstract
Astrophysical Journal v.416, p.536
Astronomy and Astrophysics
Astronomy
33
Galaxies: Quasars: General, Galaxies: Individual Ngc Number: Ngc 5548, Galaxies: Seyfert, Ultraviolet: Galaxies
Scientific paper
This is the second in a series of papers examining variable absorption components in the broad emission lines of Seyfert 1 galaxies. In an IUE survey of a complete sample of CfA Seyfert galaxies, we find that at least 12% and perhaps as many as 27% of the objects show evidence of intrinsic absorption in C IV 1549. In this paper, we use data from an 8 month lUE campaign on NGC 5548 to study the C IV absorption component. From the observed fluxes and C IV ionization conditions, we infer that the C IV absorption occurs within (14 pc)r6-1/2 of the nucleus. The C IV absorption feature is blueshifted by ˜1200 km s-1 from the systemic velocity of the galaxy and varies on a timescale of 4 days or less, indicating that ne ≥ 5 × 105 cm-3 from recombination-response arguments. The C IV absorption equivalent width strongly anticorrelates with continuum flux at 1570 Å.
The broad-line region must be at least partially covered by the absorbing region, and the central wavelength of the broad-line region corresponds to that of the maximum absorption. Standard broad-line clouds cannot account for the absorption feature, and the absorbing material must be optically thin and dispersed in velocity space. We propose a relationship between broad absorption line (BAL) QSOs and Seyfert 1 galaxies with absorption, and we suggest that the latter may be a low-luminosity, low-redshift manifestation of the BAL phenomenon in quasars. The high frequency of occurrence may represent a statistical effect of outflow viewing angle on the sky.
Sachs Elise R.
Shull Michael J.
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