Magnetically driven accretion disc winds: the role of gas thermodynamics and comparison to ultra-fast outflows

Wang, Weixiao; Bu, De-Fu; Yuan, Feng

doi:10.1093/mnras/stac1348

Cited by 9 publications

(3 citation statements)

References 44 publications

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“…Nuclear winds are intimately related to mass accretion through the conservation of angular momentum, and they are likely magnetically driven in most cases (e.g., Reynolds 2012). More recently, Wang et al (2022) performed MHD simulations of winds from thin accretion disks. The authors suggested that events resembling observed UFOs can certainly be generated within about 600r S .…”

Section: Magnetohydrodynamic Disk-wind Scenariomentioning

confidence: 99%

Dynamical complexity in microscale disk-wind systems

Fiore,

Gaspari,

Luminari

et al. 2024

A&A

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Powerful winds at accretion-disk scales have been observed in the past 20 years in many active galactic nuclei (AGN). These are the so-called ultrafast outflows (UFOs). Outflows are intimately related to mass accretion through the conservation of angular momentum, and they are therefore a key ingredient of most accretion disk models around black holes (BHs). At the same time, nuclear winds and outflows can provide the feedback that regulates the joint BH and galaxy growth. We reconsidered UFO observations in the framework of disk-wind scenarios, both magnetohydrodynamic disk winds and radiatively driven winds. We studied the statistical properties of observed UFOs from the literature and derived the distribution functions of the ratio $ of the mass-outflow and -inflow rates and the ratio $ of the mass-outflow and the Eddington accretion rates. We studied the links between $ and $ and the Eddington ratio $ L_ bol L_ Edd $. We derived the typical wind-activity history in our sources by assuming that it can be statistically described by population functions. We find that the distribution functions of $ and $ can be described as power laws above some thresholds, suggesting that there may be many wind subevents for each major wind event in each AGN activity cycle, which is a fractal behavior. We then introduced a simple cellular automaton to investigate how the dynamical properties of an idealized disk-wind system change following the introduction of simple feedback rules. We find that without feedback, the system is overcritical. Conversely, when feedback is present, regardless of whether it is magnetic or radiation driven, the system can be driven toward a self-organized critical state. Our results corroborate the hypothesis that AGN feedback is a necessary key ingredient in disk-wind systems, and following this, in shaping the coevolution of galaxies and supermassive BHs.

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Section: Magnetohydrodynamic Disk-wind Scenariomentioning

confidence: 99%

Dynamical complexity in microscale disk-wind systems

Fiore,

Gaspari,

Luminari

et al. 2024

A&A

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“…Although there have been numerous theoretical studies on the wind launched from a thin disc (e.g. Wang, Bu & Yuan 2022 ), since the observational data is very abundant, we directly use the statistical results of the mass flux and velocity of wind as a function of L bol (Gofford et al 2015 ). Following Yuan et al ( 2018 ), the mass flux and velocity of the wind from cold mode can be described as In equation ( 6), we set 10 5 km s −1 as an upper limit of the wind since observations indicate that the velocity of the wind will be saturated at this value.…”

Section: Agn Physicsmentioning

confidence: 99%

Active galactic nuclei feedback in an elliptical galaxy (III): the impacts and fate of cosmological inflow

Zhu

Yuan

et al. 2023

Monthly Notices of the Royal Astronomical Society

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The cosmological inflow of a galaxy is speculated to be able to enter the galaxy and enhance the star formation rate (SFR) and black hole accretion rate (BHAR). In this paper, by performing high-resolution hydrodynamic simulations in the framework of MACER, we investigate the fate of the inflow and its impacts on the evolution of a massive elliptical galaxy. The inflow properties are adopted from the cosmological simulation IllustrisTNG. We find that the inflow gas hardly enters but is blocked beyond ∼20 kpc from the central galaxy and becomes part of the circumgalactic medium (CGM). The gas pressure gradient, mainly contributed by the thermalized stellar wind and subdominant contributed by the energy input from the AGN, balances gravity and prevents the inflow from entering the galaxy. The SFR and BHAR are almost not affected by the normal inflow. However, if the rate of cosmological inflow were increased by a factor of 3, a small fraction of the inflow would enter the galaxy and contribute about 10% of the gas in the galaxy. In this case, the gas density in the galaxy would increase by a factor of $\gtrsim $ 20. This increase is not because of the additional gas supply by the inflow but due to the increase of gas density and pressure in the CGM caused by the inflow. Consequently, the SFR and BHAR would increase by a factor of ∼5 and ∼1000, respectively. Finally, AGN feedback can perturb the motion of the inflow and heat the CGM through its intermittent outbursts.

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“…Highly blueshifted absorption lines are frequently detected in the UV and X-ray spectra of AGNs (e.g., Tombesi et al 2010;Serafinelli et al 2019), indicating the presence of high-velocity winds/outflows in these systems. These outflows, particularly ultrafast ones, are presumed to originate in the inner regions of accretion disks and could be powered by the magnetic field (e.g., Wang et al 2022). Recent observations have also validated the existence of outflows in CL-AGNs, such as MrK590 (Gupta et al 2015) and NGC1566 .…”

Section: Introductionmentioning

confidence: 95%

Magnetized Accretion Disks with Outflows for Changing-look AGNs

Wu,

2023

ApJ

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Changing-look active galactic nuclei (CL-AGNs) challenge the standard accretion theory, owing to their rapid variability. Recent numerical simulations have shown that, for the sub-Eddington accretion case, the disk is magnetic pressure–dominated, thermally stable, and geometrically thicker than the standard disk. In addition, outflows were found in the simulations. Observationally, high blueshifted velocities absorption lines indicate that outflows exist in AGNs. In this work, based on the simulation results, we investigate the magnetic pressure–dominated disk, and find that the accretion timescale is significantly shorter than that of the standard thin disk. However, such a timescale is still longer than that of the CL-AGNs. Moreover, if the role of outflows is taken into account, then the accretion timescale can be shortened even further. By the detailed comparison of the theoretical accretion timescale with the observations, we propose that the magnetic pressure–dominated disk incorporating outflows can be responsible for the rapid variability of CL-AGNs.

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Magnetically driven accretion disc winds: the role of gas thermodynamics and comparison to ultra-fast outflows

Cited by 9 publications

References 44 publications

Dynamical complexity in microscale disk-wind systems

Dynamical complexity in microscale disk-wind systems

Active galactic nuclei feedback in an elliptical galaxy (III): the impacts and fate of cosmological inflow

Magnetized Accretion Disks with Outflows for Changing-look AGNs

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