The case for inflow of the broad-line region of active galactic nuclei

Abstract

The high-ionization lines of the broad-line region (BLR) of thermal active galactic nuclei (AGNs) show blueshifts of a few hundred km/s to several thousand km/sec with respect to the low-ionization lines. This has long been thought to be due to the high-ionization lines of the BLR arising in a wind of which the far side of the outflow is blocked from our view by the accretion disc. Evidence for and against the disc-wind model is discussed. The biggest problem for the model is that velocity-resolved reverberation mapping repeatedly fails to show the expected kinematic signature of outflow of the BLR. The disc-wind model also cannot readily reproduce the red side of the line profiles of high-ionization lines. The rapidly falling density in an outflow makes it difficult to obtain high equivalent widths. We point out a number of major problems with associating the BLR with the outflows producing broad absorption lines. An explanation which avoids all these problems and satisfies the constraints of both the line profiles and velocity-resolved reverberation-mapping is a model in which the blueshifting is due to scattering off material spiraling inwards with an inflow velocity of half the velocity of the blueshifting. We discuss how recent reverberation mapping results are consistent with the scattering-plus-inflow model but do not support a disc-wind model. We propose that the anti-correlation of the apparent redshifting of H$\beta$ with the blueshifting of CIV is a consequence of contamination of the red wings of H$\beta$ by the broad wings of [O III].

15 pages, 15 figures. To appear in special issue of Astrophysics and Space Science, "Spectral Line Shapes in Astrophysics"

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Cited by in corpus (10)

• The Sloan Digital Sky Survey Reverberation Mapping Project: Velocity Shifts of Quasar Emission Lines
• Space Telescope and Optical Reverberation Mapping Project. V. Optical Spectroscopic Campaign and Emission-Line Analysis for NGC 5548
• Testing AGN outflow and accretion models with CIV and HeII emission line demographics in z=2 quasars
• Partial dust obscuration in active galactic nuclei as a cause of broad-line profile and lag variability, and apparent accretion disc inhomogeneities
• Test of the Formation mechanism of the Broad Line Region in Active Galactic Nuclei
• A disc wind model for blueshifts in quasar broad emission lines
• Using the Properties of Broad Absorption Line Quasars to Illuminate Quasar Structure
• A comparative study of the physical properties for a representative sample of Narrow and Broad-line Seyfert galaxies
• X-ray selected broad absorption line quasars in SDSS-V: BALs and non-BALs span the same range of X-ray properties
• The detections of inflowing gas from narrow absorption lines at the parsec scale