A Structure for Quasars

By M. Elvis. 2000

633 citations recorded by the source corpus.

This paper proposes a simple, empirically derived, unifying structure for the inner regions of quasars. This structure is constructed to explain the broad absorption line regions (BALRs) and the narrow "associated" ultraviolet and X-ray "ionized" absorbers (NALs) and is also found to explain the broad emission line regions (BELRs) and several scattering features, including a substantial fraction of the broad X-ray Fe-K emission line and the biconical extended narrow emission line region (ENLR) structures seen on large kiloparsec scales in Seyfert images. The model proposes that a funnel-shaped thin shell outflow creates all of these features. The wind arises vertically from a narrow range of radii on a disk at BELR velocities. Radiation force then accelerates the flow radially, so that it bends outward to a cone angle of ~60° and has a divergence angle of ~6°, to give a covering factor of ~10%. When the central continuum is viewed from the side, through this wind, narrow high-ionization "associated" ultraviolet absorption lines and the X-ray "ionized absorbers" are seen, as in many low-luminosity active galactic nuclei (AGNs). When viewed end-on, the full range of velocities is seen in absorption with a large total column density, giving rise to the broad absorption line systems seen in a minority of quasars, the BAL QSOs. The wind is both warm (~106 K) and highly ionized. This warm highly ionized medium (WHIM) has a density of ~109 cm-3, putting it in pressure equilibrium with the BELR clouds; the BELR is then a cool phase embedded in the overall outflow, avoiding cloud destruction through shear. The wind has the correct ionization parameter and filling factor for this. The high- and low-ionization zones of the BELR correspond to the cylindrical and conical regions of the wind, since the former is exposed to the full continuum while the latter receives only the continuum filtered by the former. The warm wind is significantly Thomson thick along the radial flow direction, producing the polarized optical continuum found in BALs, but is only partially ionized, creating a broad fluorescent 6.4 keV Fe-K emission line and greater than 10 keV Compton hump. The conical shell outflow can produce a biconical matter-bounded NELR. Luminosity-dependent changes in the structure, reducing the cylindrical part of the flow or increasing the mean angle to the disk axis and decreasing the wind opening angle, may explain the UV and X-ray Baldwin effects and the greater prevalence of obscuration in low-luminosity AGNs.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/80018d93ba27b6a8ed2b00b2360ca719f1bb3f3d

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Citations in the corpus

Accretion disk wind in the AGN broad-line region: Spectroscopically resolved line profile variations in Mrk 110 ? (2003, background): “Other authors published further indications for a disk-like configuration of the broad-line region in AGN based on theoretical models or observational data (Bottorff et al. 1997; Collin-Souffrin et al. 1988; Elvis 2000; K¨onigl & Kartje 1994).”
A strong redshift dependence of the broad absorption line quasar fraction (2010, background): “In some models the BAL phenomenon arises from preferred viewing angles towards the central regions and the demographics of BALQSOs among the quasar population may also help constrain the parameters of unified models (e.g. Elvis 2000).”
UNIFICATION OF LUMINOUS TYPE 1 QUASARS THROUGH C iv EMISSION (2010, background): “We emphasize that the rapid growth (and general acceptance) of the disk-wind model (e.g., Murray et al. 1995; Elvis 2000; Proga et al. 2000) postdates much of the work on the BELR (including Boroson & Green 1992).”
Unification of X-ray winds in Seyfert galaxies: from ultra-fast outflows to warm absorbers (2012, background): “At these locations, dust would be present at the disc surface and it could be uplifted and become embedded in the outflow, explaining its presence in some WA observations (Königl & Kartje 1994; Elvis 2000; Kazanas et al. 2012).”
A Cosmological Framework for the Co-Evolution of Quasars, Supermassive Black Holes, and Elliptical Galaxies. II. Formation of Red Ellipticals (2007, background): “…to quasars see highly energetic (kseveral 103 km s 1) broad absorption line (BAL) outflows, and it is likely that all bright quasars exhibit some such BALs (although they may not be visible owing to geometric effects; Reichard et al. 2003; Elvis 2000; Gallagher et al. 2006; Priddey et al. 2007).”
Warm Absorbers in Active Galactic Nuclei: A Multitemperature Wind (2001, background): “…suggestions include evaporation o† ““ bloated stars ÏÏ in the BLR (Netzer 1996), gas, evaporated o† the torus obscuring the nucleus, that becomes the scattering gas seen in type 2 Seyfert galaxies (Krolik & Kriss 1995), and a wind driven o† the accretion disk (Elvis 2000 ; Bottor† et al. 2000).”
X-shooter reveals powerful outflows in z ∼ 1.5 X-ray selected obscured quasi-stellar objects (2014, background): “…et al. 2010; Rupke & Veilleux 2011; Villar-Martín et al. 2011; Rodríguez-Zaurín et al. 2013; Zhang et al. 2011; Westmoquette et al. 2012; Rupke & Veilleux 2013; Harrison et al. 2014; McElroy et al. 2014; see also Elvis 2000 for a discussion on the ubiquitous presence of winds in the AGN structure).”
Systematic effects in measurement of black hole masses by emission-line reverberation of active galactic nuclei: Eddington ratio and inclination (2006, background): “In this model, the broad emission lines are emitted from the base of the disk winds (see also Elvis 2000).”
AGN wind scaling relations and the co-evolution of black holes and galaxies (2017, background): “Although wind observations are very common in AGN (see Elvis 2000; Veilleux et al. 2005; and Fabian 2012, for reviews), most studies concern ionised gas and uncertain spatial scales.”
Evidence for ultra-fast outflows in radio-quiet AGNs - I. Detection and statistical incidence of Fe K-shell absorption lines (2010, background): “However, we warn again that these velocities are actually only lower limits, because they depend onthe unknown inclination angle of the outflows with respect to the line of sight (e.g. Elvis 2000).”
Biases in Virial Black Hole Masses: An SDSS Perspective (2007, background): “Such disk-wind models are compelling for a variety of reasons, particularly their success in explaining the properties of broad absorption line quasars (e.g., Murray et al. 1995; Proga et al. 2000; Elvis 2000).”
The Blast Wave Model for AGN Feedback: Effects on AGN Obscuration (2008, methodology): “As for the outflow geometry, our model also applies to segments of spherical shells expanding outwards, generated by winds driven by a spherically symmetric AGN radiation field; these segments may not uniformly cover the central source, as in the conical distribution of Elvis (2000).”
DISCOVERY OF ULTRA-FAST OUTFLOWS IN A SAMPLE OF BROAD-LINE RADIO GALAXIES OBSERVED WITH SUZAKU (2010, background): “In other words, they depend on whether we are actually looking directly down to the outflowing stream or intercepting only part of it (e.g., Elvis 2000).”
The Effect of Radiation Pressure on Virial Black Hole Mass Estimates and the Case of Narrow-Line Seyfert 1 Galaxies (2008, methodology): “…upon observational evidence for outflows in the BLR, alternative models have been proposed in which part of the BLR is in the form of a disk wind (e.g. Murray & Chiang 1995; Chiang & Murray 1996; Elvis 2000; Collin & Huré 2001; Proga et al. 2000; Proga 2007; Everett 2005 and references therein).”
The Intrinsic Fraction of Broad Absorption Line Quasars (2008, methodology): “This fits in well with unified models, in which orientation is the major factor determining the observational appearance of AGN (e.g. Elvis 2000).”
Imaging bright-spots in the accretion flow near the black hole horizon of Sgr A* (2005, background): “The case is further complicated by the existence of alternative interpretations (see e.g. Elvis 2000; You et al. 2003).”
Simultaneous X-ray and UV spectroscopy of the Seyfert galaxy NGC 5548 - II. Physical conditions in the X-ray absorber (2005, background): “The model by Elvis (2000) prefers a localized stream, however there are some problems with modeling 5 different localized outflows as radiation pressure would merge them with time (Proga, private communication).”
Completion of a Survey and Detailed Study of Double-peaked Emission Lines in Radio-loud Active Galactic Nuclei (2003, background): “This idea is by no means new; it was suggested, for example, by Murray et al. (1995) to explain broad-absorption line quasars and by Elvis (2000) to explain the absorption features observed in the X-ray spectra of quasars.”