Polarization in broad emission lines of active galactic nuclei

Shablovinskaya, Elena; Savić, Đorđe

doi:10.1002/asna.20210089

Cited by 4 publications

(3 citation statements)

References 70 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To better understand the CL nature of NGC 3516, we go on to consider the spectro-polarimetric observations of a number of AGNs, where equatorial scattering in the inner part of the dusty torus is expected (see e.g., Smith et al 2005;Popović et al 2022). The reverberation in the polarised broad lines, on the other hand, indicates that the scattering equatorial region is most likely coincident with the dust sublimation region, which is smaller than the estimated inner dusty torus radius (see e.g., Mrk 6 in Shablovinskaya et al 2020).…”

Section: Role Of Dust and Accretion In The CL Mechanismmentioning

confidence: 99%

Long-term optical spectral monitoring of a changing-look active galactic nucleus NGC 3516

Ilić¹,

Burenkov²,

Álvarez³

2023

A&A

Self Cite

View full text Add to dashboard Cite

Context. We analyze the broad Hβ line profile variability of a “changing look” active galactic nucleus (CL-AGN) NGC 3516 over an extensive period of 25 years (from 1996 to 2021). The observed change in the broad line profile may indicate a change in the geometry of the broad line region (BLR). The main objective is to follow and understand the change in the BLR over a long period as well as its connection to the CL mechanism. Aims. Using spectral line profiles, we aim to explore changes in the kinematics and dimensions of the BLR in NGC 3516. We consider two possible scenarios: the changes in the broad-line emission are either caused by a decrease of ionisation continuum emission or by the BLR obscuration by outer dusty regions. With this investigation, we aim to clarify the CL mechanism of this AGN. Methods. We analyzed the spectral band around the Hβ line as well as the broad Hβ line parameters and how they change over time. We modelled the broad-line profiles, assuming that there is an emission from the accretion disc superposed with emission from a surrounding region that is outside the disc. Results. We find that in the type 1 activity phase occurring when the strong broad emission lines are observed, the BLR is very complex. There is a clear disc-like BLR that contributes to the broad line wings and an additional intermediate line region (ILR) that contributes to the line core. In the high-activity phase, the ILR emission is close to the center of the line, although in some cases, it is slightly shifted to the red. In the low-activity phase (i.e. type 2 phase), the ILR component has a significant shift to the blue, indicating an outflow. Conclusions. We propose that the changing-look mechanism in NGC 3516 is rather connected with the intrinsic effects than with an outer obscuring region. It may still be possible that the dust plays an important role in the low-activity phase when it is coming from within the BLR, leading to a dusty BLR. In this way, it would cause a decrease in the ionisation and recombination rates.

show abstract

Section: Role Of Dust and Accretion In The CL Mechanismmentioning

confidence: 99%

Long-term optical spectral monitoring of a changing-look active galactic nucleus NGC 3516

Ilić¹,

Burenkov²,

Álvarez³

2023

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…The amount of such outflows is difficult to estimate, but it has been argued that energy and momentum lead to massive outflows that can be even optically thick for electron scattering (King 2010). The polarization level is rather low, from a fraction of a percent to a few percent (see e.g., Capetti et al 2021;Popović et al 2022, for most recent extensive measurements). Such a polarization level is consistent with the optical depth of scatterers on the order of 1, as it largely depends on the viewing angle (Lira et al 2020).…”

Section: Calculation Of Line Profilementioning

confidence: 99%

Radiation pressure on dust explaining the low ionized broad emission lines in active galactic nuclei

Naddaf

2022

A&A

View full text Add to dashboard Cite

Context. Broad emission lines are the most characteristic features in the spectra of galaxies with an active galactic nucleus (AGN). They mostly show either single-peaked or double-peaked profiles and originate from a complex dynamics of the likely discrete clouds moving in a spatially extended region known as the broad line region (BLR). Aims. In this paper, we present a large grid of results, which is used to test the model based on calculations of the spectral line generic profiles. Methods. We followed a non-hydrodynamical single-cloud approach to BLR dynamics based on a radiatively dust-driven model. We previously showed in detail that the 2.5D version of the model could provide us with the 3D geometry of the BLR. Results. We show that the shape of profiles not only depends on the accretion rate of the source, the black hole mass, and the viewing angle, but it is most significantly affected by the adopted dust-to-gas mass ratio regulating the strength of the radiation pressure. We also show that the model can aptly explain the low ionized broad emission lines of the mean spectrum of quasars, such as MgII and Hβ. Conclusions. The radiatively dust-driving mechanism can appropriately account for the low-ionized part of BLR of AGNs.

show abstract

“…Irwin et al 1989;Sluse et al 2011;Guerras et al 2013), polarization of broad emission-lines (e.g. Savić et al 2018Savić et al , 2021Capetti et al 2021;Popović et al 2022), singleepoch virial estimates (e.g. Vestergaard 2002;McLure & Jarvis 2002;McLure & Dunlop 2004;Greene & Ho 2005;, accretion disc fitting (e.g.…”

Section: Introductionmentioning

confidence: 99%

Characterising SMSS J2157--3602, the most luminous known quasar, with accretion disc models

Lai¹,

Wolf²,

Onken³

et al. 2023

Preprint

View full text Add to dashboard Cite

We develop an accretion disc (AD) fitting method, utilising thin and slim disc models and Bayesian inference with the Markov-Chain Monte-Carlo approach, testing it on the most luminous known quasar, SMSS J215728.21-360215.1, at redshift 𝑧 = 4.692. With a spectral energy distribution constructed from near-infrared spectra and broadband photometry, the AD models find a black hole mass of log(𝑀 AD /𝑀 ) = 10.31 +0.17 −0.14 with an anisotropy-corrected bolometric luminosity of log (𝐿 bol /erg s −1 ) = 47.87 ± 0.10, and derive an Eddington ratio of 0.29 +0.11 −0.10 as well as a radiative efficiency of 0.09 +0.05 −0.03 . Using the near-infrared spectra, we estimate the single-epoch virial black hole mass estimate to be log(𝑀 SE /𝑀 ) = 10.33 ± 0.08, with a monochromatic luminosity at 3000Å of log (𝐿 (3000Å)/erg s −1 ) = 47.66 ± 0.01. As an independent approach, AD fitting has the potential to complement the single-epoch virial mass method in obtaining stronger constraints on properties of massive quasar black holes across a wide range of redshifts.

show abstract

Polarization in broad emission lines of active galactic nuclei

Cited by 4 publications

References 70 publications

Long-term optical spectral monitoring of a changing-look active galactic nucleus NGC 3516

Long-term optical spectral monitoring of a changing-look active galactic nucleus NGC 3516

Radiation pressure on dust explaining the low ionized broad emission lines in active galactic nuclei

Characterising SMSS J2157--3602, the most luminous known quasar, with accretion disc models

Contact Info

Product

Resources

About