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1. Dust dynamics in AGN winds: a new mechanism for multiwavelength AGN variability

   https://doi.org/10.1093/mnras/stad2460  

   Soliman, Nadine_H; Hopkins, Philip_F (August 2023, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT Partial dust obscuration in active galactic nuclei (AGNs) has been proposed as a potential explanation for some cases of AGN variability. The dust–gas mixture present in AGN tori is accelerated by radiation pressure, leading to the launching of an AGN wind. Dust under these conditions has been shown to be unstable to a generic class of fast-growing resonant drag instabilities (RDIs). In this work, we present the first numerical simulations of radiation-driven outflows that explicitly include dust dynamics in conditions resembling AGN winds. We investigate the implications of RDIs on the torus morphology, AGN variability, and the ability of radiation to effectively launch a wind. We find that the RDIs rapidly develop, reaching saturation at times much shorter than the global time-scales of the outflows, resulting in the formation of filamentary structure on box-size scales with strong dust clumping and super-Alfvénic velocity dispersions. The instabilities lead to fluctuations in dust opacity and gas column density of 10–20  per cent when integrated along mock observed lines of sight to the quasar accretion disc. These fluctuations occur over year to decade time-scales and exhibit a red-noise power spectrum commonly observed for AGNs. Additionally, we find that the radiation effectively couples with the dust–gas mixture, launching highly supersonic winds that entrain 70–90  per cent of the gas, with a factor of ≲3 photon momentum loss relative to the predicted multiple-scattering momentum loading rate. Therefore, our findings suggest that RDIs play an important role in driving the clumpy nature of AGN tori and generating AGN variability consistent with observations. 

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2. Mapping AGN winds: A connection between radio-mode AGNs and the AGN feedback cycle

   https://doi.org/10.1051/0004-6361/202451738  

   Albán, M; Wylezalek, D; Comerford, J M; Greene, J E; Riffel, R A (November 2024, Astronomy & Astrophysics)

   We present a kinematic analysis based on the large integral field spectroscopy (IFS) dataset of SDSS-IV MaNGA (Sloan Digital Sky Survey/Mapping Nearby Galaxies at Apache Point Observatory; ∼10 000 galaxies). We have compiled a diverse sample of 594 unique active galactic nuclei (AGNs), identified through a variety of independent selection techniques, encompassing radio (1.4 GHz) observations, optical emission-line diagnostics (BPT), broad Balmer emission lines, mid-infrared colors, and hard X-ray emission. We investigated how ionized gas kinematics behave in these different AGN populations through stacked radial profiles of the [O III] 5007 emission-line width across each AGN population. We contrasted AGN populations against each other (and non-AGN galaxies) by matching samples by stellar mass, [O III] 5007 luminosity, morphology, and redshift. We find similar kinematics between AGNs selected by BPT diagnostics compared to broad-line-selected AGNs. We also identify a population of non-AGNs with similar radial profiles as AGNs, indicative of the presence of remnant outflows (or fossil outflows) of past AGN activity. We find that purely radio-selected AGNs display enhanced ionized gas line widths across all radii. This suggests that our radio-selection technique is sensitive to a population in which AGN-driven kinematic perturbations have been active for longer durations (potentially due to recurrent activity) than in purely optically selected AGNs. This connection between radio activity and extended ionized gas outflow signatures is consistent with recent evidence that suggests radio emission (expected to be diffuse) originated due to shocks from outflows. We conclude that different selection techniques can trace different AGN populations not only in terms of energetics but also in terms of AGN evolutionary stages. Our results are important in the context of the AGN duty cycle and highlight integral field unit data’s potential to deepen our knowledge of AGNs and galaxy evolution. 

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3. Markarian 590: the AGN awakens

   https://doi.org/10.1093/mnrasl/slaf027  

   Palit, Biswaraj; Śniegowska, Marzena; Markowitz, Alex; Różańska, Agata; Farah, Joseph; Howell, D Andrew (March 2025, Monthly Notices of the Royal Astronomical Society: Letters)

   ABSTRACT Changing-look active galactic nucleus Mkn 590 recently underwent a sudden ‘re-ignition’, marked by substantial increases in optical/ultravilolet (UV) and X-ray continuum flux since last couple of years. Swift-XRT observations revealed the re-emergence of a soft X-ray excess as the source transitioned from a low-flux state in July 2023 to a significantly higher flux state in October 2024. This evolution was in response to an order-of-magnitude increase in extreme-UV continuum emission, detected by Swift-UVOT. Follow-up optical spectra from FLOYDS/Faulkes confirmed the enhancement of dynamically broadened Balmer lines, He ii emission, and Fe ii complex. As the Eddington fraction increased by a factor of $$\sim$$20 over the last 20 months, we found clear evidence of formation of a warm corona, strongly linked to the cold accretion disc underneath. Based on our multiwavelength study on recent data, we propose that Mkn 590 is currently becoming a Seyfert-1.2, similar to its state in 1990s. 

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4. AGN-Driven Outflows in Dwarf Galaxies

   https://doi.org/10.3847/1538-4357/ab4197  

   Manzano-King, Christina M.; Canalizo, Gabriela; Sales, Laura V. (October 2019, The Astrophysical Journal)
5. BAT AGN Spectroscopic Survey – XIII. The nature of the most luminous obscured AGN in the low-redshift universe

   https://doi.org/10.1093/mnras/stz2309  

   Bär, Rudolf E; Trakhtenbrot, Benny; Oh, Kyuseok; Koss, Michael J; Wong, O Ivy; Ricci, Claudio; Schawinski, Kevin; Weigel, Anna K; Sartori, Lia F; Ichikawa, Kohei; et al (November 2019, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT We present a multiwavelength analysis of 28 of the most luminous low-redshift narrow-line, ultra-hard X-ray-selected active galactic nuclei (AGN) drawn from the 70-month Swift/BAT all-sky survey, with bolometric luminosities of $$\log (L_{\rm bol} /{\rm erg\, s}^{-1}) \gtrsim 45.25$$. The broad goal of our study is to determine whether these objects have any distinctive properties, potentially setting them aside from lower luminosity obscured AGN in the local Universe. Our analysis relies on the first data release of the BAT AGN Spectroscopic Survey (BASS/DR1) and on dedicated observations with the VLT, Palomar, and Keck observatories. We find that the vast majority of our sources agree with commonly used AGN selection criteria which are based on emission line ratios and on mid-infrared colours. Our AGN are pre-dominantly hosted in massive galaxies (9.8 ≲ log (M*/M⊙) ≲ 11.7); based on visual inspection of archival optical images, they appear to be mostly ellipticals. Otherwise, they do not have distinctive properties. Their radio luminosities, determined from publicly available survey data, show a large spread of almost four orders of magnitude – much broader than what is found for lower X-ray luminosity obscured AGN in BASS. Moreover, our sample shows no preferred combination of black hole masses (MBH) and/or Eddington ratio (λEdd), covering 7.5 ≲ log (MBH/M⊙) ≲ 10.3 and 0.01 ≲ λEdd ≲ 1. Based on the distribution of our sources in the λEdd−NH plane, we conclude that our sample is consistent with a scenario where the amount of obscuring material along the line of sight is determined by radiation pressure exerted by the AGN on the dusty circumnuclear gas. 

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