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The Link Between the Hidden Broad Line Region and the Accretion Rate in Seyfert 2 Galaxies
Cosmology and Nongalactic Astrophysics · Submitted 25 Jan 2012
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim In the following, we will present evidence that accretion rate is also a key parameter for the presence of Hidden Broad Line Regions in Seyfert 2 galaxies.
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The abstract, sentence by sentence
In the past few years more and more pieces of evidence have been presented for a revision of the widely accepted Unified Model of Active Galactic Nuclei. A model based solely on orientation cannot explain all the observed phenomenology. In the following, we will present evidence that accretion rate is also a key parameter for the presence of Hidden Broad Line Regions in Seyfert 2 galaxies. Our sample consists of 21 sources with polarized Hidden Broad Lines and 18 sources without Hidden Broad Lines. We use stellar velocity dispersions from several studies on the CaII and Mg b triplets in Seyfert 2 galaxies, to estimate the mass of the central black holes via the Mbh-{\sigma}\ast relation. The ratio between the bolometric luminosity, derived from the intrinsic (i.e. unabsorbed) X-ray luminosity, and the Eddington luminosity is a measure of the rate at which matter accretes onto the central supermassive black hole. A separation between Compton-thin HBLR and non-HBLR sources is clear, both in accretion rate (log Lbol/LEdd = -1.9) and in luminosity (log Lbol = 43.90). When, properly luminosity-corrected, Compton-thick sources are included, the separation between HBLR and non-HBLR is less sharp but no HBLR source falls below the Eddington ratio threshold. We speculate that non-HBLR Compton-thick sources with accretion rate higher than the threshold, do possess a BLR, but something, probably related to their heavy absorption, is preventing us from observing it even in polarized light. Our results for Compton-thin sources support theoretical expectations. In a model presented by Nicastro (2000), the presence of broad emission lines is intrinsically connected with disk instabilities occuring in proximity of a transition radius, which is a function of the accretion rate, becoming smaller than the innermost stable orbit for very low accretion rates and therefore luminosities.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | In the past few years more and more pieces of evidence have been presented for a revision of the widely accepted Unified Model of Active Galactic Nuclei. | background 1.00 | 0.04 | 0.02 | asserted 0.98 |
| s1 | A model based solely on orientation cannot explain all the observed phenomenology. | background 0.76 | 0.07 | 0.04 | asserted 1.00 |
| s2 | In the following, we will present evidence that accretion rate is also a key parameter for the presence of Hidden Broad Line Regions in Seyfert 2 galaxies. | contribution 0.96 | 0.33 | 0.70 | asserted 0.81 |
| s3 | Our sample consists of 21 sources with polarized Hidden Broad Lines and 18 sources without Hidden Broad Lines. | method 0.85 | 0.79 | 0.02 | asserted 0.96 |
| s4 | We use stellar velocity dispersions from several studies on the CaII and Mg b triplets in Seyfert 2 galaxies, to estimate the mass of the central black holes via the Mbh-{\sigma}\ast relation. | method 1.00 | 0.73 | 0.02 | asserted 0.99 |
| s5 | The ratio between the bolometric luminosity, derived from the intrinsic (i.e. unabsorbed) X-ray luminosity, and the Eddington luminosity is a measure of the rate at which matter accretes onto the central supermassive black hole. | method 0.87 | 0.19 | 0.03 | asserted 1.00 |
| s6 | A separation between Compton-thin HBLR and non-HBLR sources is clear, both in accretion rate (log Lbol/LEdd = -1.9) and in luminosity (log Lbol = 43.90). | result 1.00 | 0.90 | 0.44 | asserted 1.00 |
| s7 | When, properly luminosity-corrected, Compton-thick sources are included, the separation between HBLR and non-HBLR is less sharp but no HBLR source falls below the Eddington ratio threshold. | result 0.98 | 0.88 | 0.19 | asserted 0.99 |
| s8 | We speculate that non-HBLR Compton-thick sources with accretion rate higher than the threshold, do possess a BLR, but something, probably related to their heavy absorption, is preventing us from observing it even in polarized light. | interpretation 1.00 | 0.31 | 0.12 | speculative 1.00 |
| s9 | Our results for Compton-thin sources support theoretical expectations. | interpretation 0.89 | 0.76 | 0.09 | asserted 0.89 |
| s10 | In a model presented by Nicastro (2000), the presence of broad emission lines is intrinsically connected with disk instabilities occuring in proximity of a transition radius, which is a function of the accretion rate, becoming smaller than the innermost stable orbit for very low accretion rates and therefore luminosities. | interpretation 0.60 | 0.04 | 0.07 | asserted 0.87 |
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The paper
Original abstract
In the past few years more and more pieces of evidence have been presented for a revision of the widely accepted Unified Model of Active Galactic Nuclei. A model based solely on orientation cannot explain all the observed phenomenology. In the following, we will present evidence that accretion rate is also a key parameter for the presence of Hidden Broad Line Regions in Seyfert 2 galaxies. Our sample consists of 21 sources with polarized Hidden Broad Lines and 18 sources without Hidden Broad Lines. We use stellar velocity dispersions from several studies on the CaII and Mg b triplets in Seyfert 2 galaxies, to estimate the mass of the central black holes via the Mbh-{\sigma}\ast relation. The ratio between the bolometric luminosity, derived from the intrinsic (i.e. unabsorbed) X-ray luminosity, and the Eddington luminosity is a measure of the rate at which matter accretes onto the central supermassive black hole. A separation between Compton-thin HBLR and non-HBLR sources is clear, both in accretion rate (log Lbol/LEdd = -1.9) and in luminosity (log Lbol = 43.90). When, properly luminosity-corrected, Compton-thick sources are included, the separation between HBLR and non-HBLR is less sharp but no HBLR source falls below the Eddington ratio threshold. We speculate that non-HBLR Compton-thick sources with accretion rate higher than the threshold, do possess a BLR, but something, probably related to their heavy absorption, is preventing us from observing it even in polarized light. Our results for Compton-thin sources support theoretical expectations. In a model presented by Nicastro (2000), the presence of broad emission lines is intrinsically connected with disk instabilities occuring in proximity of a transition radius, which is a function of the accretion rate, becoming smaller than the innermost stable orbit for very low accretion rates and therefore luminosities.
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References
How the literature uses it
What this paper does with the arXiv papers it cites
Papers whose main result relates to this one's
States the same result 2 papers
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In this paper I present evidence suggesting that the absence or presence of Hidden Broad Line Regions (HBLRs) in Seyfert 2 galaxies is regulated by the rate at which matter accretes onto a central supermassive black hole, in units of Eddington.
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In this paper we present evidence suggesting that the absence or presence of Hidden Broad Line Regions (HBLRs) in Seyfert 2 galaxies is regulated by the rate at which matter accretes onto a central supermassive black hole, in units of Eddington rate.
The Lack of BLR in Low Accretion Rate AGN as Evidence of their Origin in the Accretion Disk · 0.94
What it cites · 7 sentences without a confident label
Uses the method or tool of 1 paper
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For all sources of our sample, we searched the literature for [Oiii] FWHM measurements, and applied the [ref] relation to derive the stellar velocity dispersions.
A Comparison of Stellar and Gaseous Kinematics in the Nuclei of Active Galaxies · Comparison with other Works and Methodologies · 0.97
Uses data or values from 6 papers
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Our starting sample is mostly based on the spectropolarimetric surveys performed by [ref] on the Seyfert 2 galaxies included in the CfA [ref] and 12 $μ$m [ref] samples.
The Extended 12 Micron Galaxy Sample · The Sample · 0.93
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Stellar velocity dispersions ($σ_*$) were mainly taken from [ref] and [ref] .
An atlas of Calcium triplet spectra of active galaxies · The BH mass sub-selection · 1.00
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Columns: (a) Name of the object; (b) Instrument (AS: Chandra ACIS-S; PN: XMM-Newton EPIC pn; XIS: Suzaku XIS0+3) and obsid; (c) if Compton-thin, X if Compton-thick; (d) Stellar velocity dispersions; (e) Mass of the central BH in solar mass units; (f) Absorbing column density in $10^22$ cm$^-2$ units (g) Absorption corrected 2-10 keV luminosity; (h) Bolometric luminosity; (i) Accretion rate in Eddington units; (l) Extinction-corrected O [iii] ($λ 5007$ ) luminosity; (m) O [iv] ($λ25.89 μm$ ) luminosity (n) Reference for stellar velocity dispersions, HBLR (in order); References: (1) [ref] , (2) [ref] , (3) [ref] , (4) [ref] , (5) [ref] , (6) [ref] , (7) [ref] , (8) [ref] , (9 ) [ref] , (10) [ref] , (11) [ref] , (12) [ref] , (13) Other surveys
A Study of the Direct-Fitting Method for Measurement of Galaxy Velocity Dispersions · The Sample · 0.98
Compares with 1 paper
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Other authors investigated larger (but, in most cases inhomogeneous) samples to search for physical parameters responsible for the existence or absence of HBLRs in AGNs, and found often no clear indication for the existence of such a parameter [ref] .
The accretion ratios in Seyfert 2 galaxies with and without hidden broad-line regions · Comparison with other Works and Methodologies · 0.87
Cites as background 2 papers
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Different, alternative scenarios, to the intrinsic lack of a BLR, have already been proposed in the past [ref] .
The infrared luminosity of the torus and the visibility of scattered broad line emission in Seyfert 2 galaxies · Discussion · 0.94
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Different, alternative scenarios, to the intrinsic lack of a BLR, have already been proposed in the past [ref] .
On the Nature of Hidden Broad Line Regions in Seyfert 2 Galaxies · Discussion · 0.94
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