Magnetic acceleration of broad emission-line clouds in active galactic nuclei

Emmering, Robert T.; Blandford, R. D.; Shlosman, Isaac

doi:10.1086/170955

Cited by 293 publications

(314 citation statements)

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“…A potential mechanism is described by Emmering et al (1992) in the context of MHD winds. As a wind or cloud forms, the material initially contains a high amount of dust, which is a good coolant via IR thermal emission.…”

Section: The Origin Of the Absorbermentioning

confidence: 99%

A variable-density absorption event in NGC 3227 mapped withSuzakuandSwift

Markowitz

Krauß

Miniutti

et al. 2015

A&A

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Context. The morphology of the circumnuclear gas accreting onto supermassive black holes in Seyfert galaxies remains a topic of much debate. As the innermost regions of active galactic nuclei (AGN) are spatially unresolved, X-ray spectroscopy, and in particular line-of-sight absorption variability, is a key diagnostic to map out the distribution of gas. Aims. Observations of variable X-ray absorption in multiple Seyferts and over a wide range of timescales indicate the presence of clumps/clouds of gas within the circumnuclear material. Eclipse events by clumps transiting the line of sight allow us to explore the properties of the clumps over a wide range of radial distances from the optical/UV broad line region (BLR) to beyond the dust sublimation radius. Time-resolved absorption events have been extremely rare so far, but suggest a range of density profiles across Seyferts. We resolve a weeks-long absorption event in the Seyfert NGC 3227. Methods. We examine six Suzaku and 12 Swift observations from a 2008 campaign spanning five weeks. We use a model accounting for the complex spectral interplay of three absorbers with different levels of ionization. We perform time-resolved spectroscopy to discern the absorption variability behavior. We also examine the IR to X-ray spectral energy distribution (SED) to test for reddening by dust. Results. The 2008 absorption event is due to moderately-ionized (log ξ ∼ 1.2-1.4) gas covering 90% of the line of sight. We resolve the density profile to be highly irregular, in contrast to a previous symmetric and centrally-peaked event mapped with RXTE in the same object. The UV data do not show significant reddening, suggesting that the cloud is dust-free. Conclusions. The 2008 campaign has revealed a transit by a filamentary, moderately-ionized cloud of variable density that is likely located in the BLR, and possibly part of a disk wind.

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Section: The Origin Of the Absorbermentioning

confidence: 99%

A variable-density absorption event in NGC 3227 mapped withSuzakuandSwift

Markowitz

Krauß

Miniutti

et al. 2015

A&A

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show abstract

“…The outflow can transport energy, momentum, mass, heavy elements from the accretion disc and/or the vicinity of central region to the host galaxy and IGM, which regulate the efficiency of accretion onto the central supermassive black hole (e.g., Emmering et al 1992;Konigl & Kartje 1994), and influence the evolution of the host galaxy and surrounding environment (e.g., Tremonti et al 2007;Cattaneo et al 2009;Yuan & Narayan 2014;Ishibashi & Fabian 2014). Intrinsic absorption lines, including BALs, mini-BALs and NALs, are often utilized to study properties of the quasar outflow.…”

Section: Introductionmentioning

confidence: 99%

Narrow absorption lines with two observations from the Sloan Digital Sky Survey

Chen¹,

Gu²,

Chen³

et al. 2015

Monthly Notices of the Royal Astronomical Society

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We assemble 3524 quasars from Sloan Digital Sky Survey (SDSS) with repeated observations to search for variations of narrow C IVλλ1548, 1551 and Mg IIλλ2796, 2803 absorption doublets in spectral regions shortward of 7000Å at the observed frame, which corresponds to time-scales of about 150 ∼ 2643 days at quasar rest frame. In these quasar spectra, we detect 3580 C IV absorption systems with z abs = 1.5188 ∼ 3.5212, and 1809 Mg II absorption systems with z abs = 0.3948 ∼ 1.7167. In term of the absorber velocity (β) distribution at quasar rest frame, we find a substantial number of C IV absorbers with β < 0.06, which might be connected to the absorptions of quasar outflows. The outflow absorptions peak at υ ≈ 2000 km s −1 and drop rapidly below the peak value. Among 3580 C IV absorption systems, 52 systems (∼ 1.5%) show obvious variations in equivalent widths at the absorber rest frame (W r ): 16 enhanced, 16 emerged, 12 weaken, and 8 disappeared systems, respectively. We find that changes in W r λ1548 are neither related to time-scales of the two SDSS observations, nor to absorber velocities at the quasar rest frame. Variable absorptions in low-ionization species are important to constraint the physical conditions of absorbing gas. There are two variable Mg II absorption systems measured from SDSS spectra detected by Hacker et al. However, in our Mg II absorption sample, we find that neither shows variable absorption with confident levels of > 4σ for λ2796 lines and > 3σ for λ2803 lines.

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“…This would indicate outflows/winds as the loci of dust reprocessing AGN radiation into MIR. Such outflows might be powered magnetically as suggested by Emmering et al (1992), Königl & Kartje (1994) and Elitzur & Shlosman (2006). The elongated geometry of dusty obscurers is also supported by the fact that scattering cones in quasars are much narrower than predicted by torus models (Obied et al 2016).…”

Section: Discussionmentioning

confidence: 67%

Covering factors of the dusty obscurers in radio-loud and radio-quiet quasars

Gupta

Sikora

Nalewajko

2016

Mon. Not. R. Astron. Soc.

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We compare covering factors of circumnuclear dusty obscurers in radio-loud and radio-quiet quasars. The radio-loud quasars are represented by a sample of FR II quasars obtained by cross-matching a catalog of the FR II radio sources selected by van Velzen et al. with the SDSS DR7 catalog of quasars. Covering factors of FR II quasars are compared with covering factors of the radio-quiet quasars matched with them in redshift, black hole mass, and Eddingtonratio. We found that covering factors, proxied by the infrared-to-bolometric luminosity ratio, are on average slightly smaller in FR II quasars than in radio-quiet quasars, however, this difference is statistically significant only for the highest Eddington ratios. For both samples, no statistically significant dependence of a median covering factor on Eddington ratio, black hole mass, nor redshift can be claimed.

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Magnetic acceleration of broad emission-line clouds in active galactic nuclei

Cited by 293 publications

References 0 publications

A variable-density absorption event in NGC 3227 mapped withSuzakuandSwift

A variable-density absorption event in NGC 3227 mapped withSuzakuandSwift

Narrow absorption lines with two observations from the Sloan Digital Sky Survey

Covering factors of the dusty obscurers in radio-loud and radio-quiet quasars

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