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

Gupta, M. K.; Sikora, Marek; Nalewajko, Krzysztof

doi:10.1093/mnras/stw1473

Cited by 10 publications

(7 citation statements)

References 65 publications

(74 reference statements)

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“…If that is true, one might expect that structure and physics of accretion flows in such objects may differ significantly from those in radio-weak AGNs. However their averaged SEDs (spectral energy distributions) in IR, optical and UV bands are very similar (Elvis et al 1994;de Vries et al 2006;Richards et al 2006;Shang et al 2011;Gupta et al 2016), and statistically significant differences are found only in X-ray bands. Specifically, RL quasars have been found to be X-ray-louder and to have harder X-ray spectra than RQ quasars (Zamorani et al 1981;Worrall et al 1987;Wilkes & Elvis 1987).…”

Section: Introductionmentioning

confidence: 61%

“…This choice can be justified by noting: (i) that the MIR emission in AGNs is dominated by dust heated by central engine (e.g. Mateos et al 2015;Hönig & Kishimoto 2017;Zhuang et al 2018); (ii) that the 'effective' covering factors of dusty "obscurers" (circumnuclear tori/winds), defined to be the fraction of the optical/UV radiation converted by dust to the IR radiation, are very similar in RL and RQ AGNs (Ma & Wang 2013;Gupta et al 2016;Hickox et al 2017) and (iii) that at λ > 10µm the AGN dusty obscur-ers are optically thin and radiate isotropically (e.g. Mateos et al 2015).…”

Section: The Bh Masses and Eddington Ratiosmentioning

confidence: 99%

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Comparison of hard X-ray spectra of luminous radio galaxies and their radio-quiet counterparts

Gupta

Sikora

Rusinek

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We study the differences in X-ray properties of luminous radio galaxies and their radio-quiet counterparts. In order to avoid biases associated with the dependence of X-ray properties on the black hole mass and Eddington ratio, the radio-loud and radioquiet objects are selected to cover similar ranges of these parameters. Our studies are based on the X-ray data from the Swift/BAT catalogue. We confirm previous results that radio galaxies are on average X-ray-louder than radio-quiet AGNs, but find that their spectral slopes are very similar. This suggests that in radio-loud and radio-quiet AGNs the hard X-rays are produced in the same region and by the same mechanism. We argue that this region can be associated with the hot, geometrically thick, central portion of the accretion flow, where production of hard X-rays is likely to be dominated by Comptonization of the optical/UV radiation of the truncated 'cold' accretion disc by hot electrons. The larger X-ray luminosities in radio-loud AGNs may result from larger radiative efficiencies of the innermost portions of the accretion flows around faster rotating black holes.

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Section: Introductionmentioning

confidence: 61%

Section: The Bh Masses and Eddington Ratiosmentioning

confidence: 99%

Comparison of hard X-ray spectra of luminous radio galaxies and their radio-quiet counterparts

Gupta

Sikora

Rusinek

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…A detailed study on the evolution of covering factor in radio-quiet and the radio-loud source was recently done by Gupta et al (2016). They had more number of sources than we have.…”

Section: Discussionmentioning

confidence: 99%

Viewing angle observations and effects of evolution with redshift, black hole mass, and Eddington ratio in quasar based cosmology

Prince,

Hryniewicz,

Panda

et al. 2021

Preprint

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This study is focused on the observational measurement of the viewing angle of individual quasars by modeling the broadband quasar spectrum ranging from the infra-red (IR) to soft X-ray band. Sources are selected from various published catalogs, and their broadband quasi-simultaneous spectral data points were collected and used to model. We started with COSMOS sample of type-1 sources which have broadband photometric points. To include more data points we cross-matched the COSMOS with the SDSS DR14 quasar catalog, and eventually we find 90 sources which have broadband data ranging from IR to soft X-ray. The broadband spectral energy distribution (SED) modeling is done in Xspec by using the optxagnf and the SKIRTOR models for the X-ray, UV, Optical, and IR regimes for each source. The whole sample is divided into four bins with respect to redshift, black hole (BH) mass, and Eddington ratio with an equal number of sources in each bin. The viewing angle is estimated in each bin, and its evolution with respect to redshift, BH mass, and Eddington ratio is examined. In result, we did not find any significant evolution of viewing angle with those parameters within the 95% confidence interval. We conclude that the use of quasars in cosmology to determine the expansion rate of the universe is therefore justified, and biases are not expected.

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“…It is known that the mid-IR spectra and IR-to-optical flux ratios are very similar in RL and RQ quasars (e.g., Shang et al 2011;Gupta et al 2016), and dust torus may also be present in most RL quasars if not all. We conjecture that, the hot gas feeding the black hole co-exists with the dust clumps in a region beyond the circularization radius, and the dynamics of the hot gas is not altered significantly by the motion of the dust clumps in the torus.…”

Section: Discussionmentioning

confidence: 99%

On the Radio Dichotomy of Active Galactic Nuclei

Cao

2016

ApJ

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It is still a mystery why only a small fraction of active galactic nuclei (AGNs) contain relativistic jets. A strong magnetic field is a necessary ingredient for jet formation, however, the advection of the external field in a geometrically thin disk is inefficient. Gas with a small angular velocity may fall from the Bondi radius R B nearly freely to the circularization radius R c , and a thin accretion disk is formed within R c . We suggest that the external magnetic field is substantially enhanced in this region, and the magnetic field at R c can be sufficiently strong to drive outflows from the disk if the angular velocity of the gas is low at R B . The magnetic field is efficiently dragged in the disk, because most angular momentum of the disk is removed by the outflows that lead to a significantly high radial velocity. The strong magnetic field formed in this way may accelerate jets in the region near the black hole, either by the Blandford-Payne or/and Blandford-Znajek mechanisms. We suggest that the radio dichotomy of AGNs predominantly originates from the angular velocity of the circumnuclear gas. An AGN will appear as a radio-loud (RL) one if the angular velocity of the circumnuclear gas is lower than a critical value at the Bondi radius, otherwise, it will appear as a radio-quiet (RQ) AGN. This is supported by the observations that RL nuclei are invariably hosted by core galaxies. Our model suggests that the mass growth of the black holes in RL quasars is much faster than that in RQ quasars with the same luminosity, which is consistent with the fact that the massive black holes in RL quasars are systematically a few times heavier than those in their RQ counterparts.

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

Cited by 10 publications

References 65 publications

Comparison of hard X-ray spectra of luminous radio galaxies and their radio-quiet counterparts

Comparison of hard X-ray spectra of luminous radio galaxies and their radio-quiet counterparts

Viewing angle observations and effects of evolution with redshift, black hole mass, and Eddington ratio in quasar based cosmology

On the Radio Dichotomy of Active Galactic Nuclei

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