Spiral arms in broad-line regions of active galactic nuclei

Wang, J.-M.; Du, Pu; Songsheng, Yu-Yang; Li, Y.-R.

doi:10.1051/0004-6361/202142989

Cited by 8 publications

(2 citation statements)

References 126 publications

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“…Note that in the first term ρ 0 corresponds to the surface mass density of the gas, which is much smaller then the stellar one, so that the corresponding rotational velocity has a smaller value than the stellar one, but still it has a finite contribution to the intensity of the rotational velocity of the galactic disk. As far as the accretion disks are concerned, the proposed solution gives a better alternative for the analysis of BLR dynamics, unlike the linear density wave theory (Wang et al 2022;Du & Wang 2023), since the linear structure would be blown up (due to dispersive effects) even before it could be caught up by observer, while the solitary structure can persist even several days, depending on the central mass and distance. However, in order to apply the proposed solution in the accretion disk it is necessary to implement the finite thickness affect (Vukcevic 2014), formation of the solitary vorticies (Vukcevic 2019), and magnetic and radiative dissipation effects.…”

Section: Discussionmentioning

confidence: 99%

Nonlinear Density Wave Theory in a Gaseous Disk

Vukcevic

2023

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A nonlinear solution for the gaseous component of a galactic disk has been derived self-consistently using fluid description and reductive perturbation theory. We show that gas follows a spiral pattern, similarly to the stellar component; but the spirals are slightly separated due to different relevant parameters, as observations suggest. This analytical solution provides an additional contribution to a better understanding of rotation velocity curves of spiral galaxies. Since the proposed approach, and consequently solution, can be used in various astrophysical dynamical systems, we keep as general as possible a form of the calculus. We underline differences between the stellar and gaseous cases, and we apply this solution roughly on the gaseous disk component dynamics pointing out the importance of the nonlinear approach.

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Section: Discussionmentioning

confidence: 99%

Nonlinear Density Wave Theory in a Gaseous Disk

Vukcevic

2023

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“…Gilbert et al (1999), Storchi-Bergmann et al (2003), Schimoia et al (2012), andStorchi-Bergmann et al (2017) assumed an analytical form for the spiral arms and explained the double-peaked profiles of the broad emission lines in AGNs, but similarly did not include any dynamical physics. As the first paper of this series, Wang et al (2022) used notions of density wave theory of spiral galaxies (e.g., Lin & Shu 1964, 1966Lin et al 1969), which applies to self-gravitating disks (Goldreich & Tremaine 1979), to investigate BLRs for the first time (hereafter Paper I). Paper I explores the possibility of density waves in BLRs through discussing their physical conditions, and focuses on the simplest cases of tight-winding arms with short wavelengths and small pitch angles (adopting the formalism of the tight-winding approximation).…”

Section: Introductionmentioning

confidence: 99%

Spiral arms in broad-line regions of active galactic nuclei

Wang

2023

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There is growing evidence that broad-line regions (BLRs) in active galactic nuclei (AGNs) have regular substructures, such as spiral arms. This is supported by the fact that the radii of BLRs measured by reverberation mapping (RM) observations are generally consistent with the self-gravitating regions of accretion disks. We showed in Paper I that the spiral arms excited by the gravitational instabilities in these regions may exist in some disk-like BLRs. Here, in the second paper of the series, we investigate the loosely wound spiral arms excited by gravitational instabilities in disk-like BLRs and present their observational characteristics. We solve the governing integro-differential equation by a matrix scheme. The emission-line profiles, velocity-delay maps, and velocity-resolved lags of the BLR spiral arms are calculated. We find that the spiral arms can explain some of the phenomena seen in observations: (1) different asymmetries in the emission-line profiles in the mean and rms spectra; (2) complex subfeatures (incomplete ellipse) in some velocity-delay maps, for example that of NGC 5548; and (3) the short timescales of the asymmetry changes in emission-line profiles (rms spectra). These features are attractive for modeling the observed line profiles and the properties of reverberation, and for revealing the details of the BLR geometry and kinematics.

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The transient event in NGC 1566 from 2017 to 2019

Ochmann,

Kollatschny,

Probst

et al. 2024

A&A

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is a local face-on Seyfert galaxy and is known for exhibiting recurrent outbursts that are accompanied by changes in spectral type. The most recent transient event occurred from 2017 to 2019 and was reported to be accompanied by a change in Seyfert classification from Seyfert 1.8 to Seyfert 1.2. We aim to study the transient event in detail by analyzing the variations in the optical broad-line profiles. In particular, we intend to determine the structure and kinematics of the broad-line region. We analyzed data from an optical spectroscopic variability campaign of taken with the 9.2\,m Southern African Large Telescope (SALT) between July 2018 and October 2019 triggered by the detection of hard X-ray emission in June 2018. We supplemented this data set with optical to near-infrared (NIR) spectroscopic archival data taken by VLT/MUSE in September 2015 and October 2017, and investigated the emission from different line species during the event. exhibits pronounced spectral changes during the transient event. We observe the emergence and fading of a strong power-law-like blue continuum as well as strong variations in the Balmer He i and He ii lines and the coronal lines Fe vii Fe X and Fe XI . Moreover, we detect broad double-peaked emission line profiles of O i and the Ca ii triplet. This is the first time that genuine double-peaked O i and Ca ii emission in AGN is reported in the literature. All broad lines show a clear redward asymmetry with respect to their central wavelength and we find indications for a significant blueward drift of the total line profiles during the transient event. The profiles and the FWHM of the Balmer lines remain largely constant during all observations. We show that the double-peaked emission line profiles are well approximated by emission from a low-inclination, relativistic eccentric accretion disk, and that single-peaked profiles can be obtained by broadening due to scale-height-dependent turbulence. Small-scale features in the O i and Ca ii lines suggest the presence of inhomogeneities in the broad-line region. We conclude that the broad-line region in is dominated by the kinematics of a relativistic eccentric accretion disk. The broad-line region can be modeled to be vertically stratified with respect to scale-height turbulence with O i and Ca ii being emitted close to the disk in a region with high (column) density, while the Balmer and helium lines are emitted at greater scale height above the disk. The observed blueward drift might be attributed to a low-optical-depth wind launched during the transient event. Except for this wind, the observed kinematics of the broad-line region remain largely unchanged during the transient event.

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Spiral arms in broad-line regions of active galactic nuclei

Cited by 8 publications

References 126 publications

Nonlinear Density Wave Theory in a Gaseous Disk

Nonlinear Density Wave Theory in a Gaseous Disk

Spiral arms in broad-line regions of active galactic nuclei

The transient event in NGC 1566 from 2017 to 2019

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