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Artykuły w czasopismach na temat „AGN-Driven Turbulence”
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Brüggen, M., i E. Scannapieco. "AGN-driven Turbulence in Galaxy Clusters". EAS Publications Series 44 (2010): 63–68. http://dx.doi.org/10.1051/eas/1044011.
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Wittor, D., i M. Gaspari. "Dissecting the turbulent weather driven by mechanical AGN feedback". Monthly Notices of the Royal Astronomical Society 498, nr 4 (10.09.2020): 4983–5002. http://dx.doi.org/10.1093/mnras/staa2747.
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ABSTRACT Turbulence in the intracluster, intragroup, and circumgalactic medium plays a crucial role in the self-regulated feeding and feedback loop of central supermassive black holes. We dissect the 3D turbulent ‘weather’ in a high-resolution Eulerian simulation of active galactic nucleus (AGN) feedback, shown to be consistent with multiple multiwavelength observables of massive galaxies. We carry out post-processing simulations of Lagrangian tracers to track the evolution of enstrophy, a proxy of turbulence, and its related sinks and sources. This allows us to isolate in depth the physical processes that determine the evolution of turbulence during the recurring strong and weak AGN feedback events, which repeat self-similarly over the Gyr evolution. We find that the evolution of enstrophy/turbulence in the gaseous halo is highly dynamic and variable over small temporal and spatial scales, similar to the chaotic weather processes on Earth. We observe major correlations between the enstrophy amplification and recurrent AGN activity, especially via its kinetic power. While advective and baroclinc motions are always subdominant, stretching motions are the key sources of the amplification of enstrophy, in particular along the jet/cocoon, while rarefactions decrease it throughout the bulk of the volume. This natural self-regulation is able to preserve, as ensemble, the typically observed subsonic turbulence during cosmic time, superposed by recurrent spikes via impulsive anisotropic AGN features (wide outflows, bubbles, cocoon shocks). This study facilitates the preparation and interpretation of the thermo-kinematical observations enabled by new revolutionary X-ray integral field unit telescopes, such as XRISM and Athena.
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Hu, Haojie, Yu Qiu, Marie-Lou Gendron-Marsolais, Tamara Bogdanović, Julie Hlavacek-Larrondo, Luis C. Ho, Kohei Inayoshi i Brian R. McNamara. "Signature of Supersonic Turbulence in Galaxy Clusters Revealed by AGN-driven Hα Filaments". Astrophysical Journal Letters 929, nr 2 (1.04.2022): L30. http://dx.doi.org/10.3847/2041-8213/ac6601.
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Abstract The hot intracluster medium (ICM) is thought to be quiescent with low observed velocity dispersions. Surface brightness fluctuations of the ICM also suggest that its turbulence is subsonic with a Kolmogorov scaling relation, indicating that the viscosity is suppressed and the kinetic energy cascades to small scales unscathed. However, recent observations of the cold gas filaments in galaxy clusters find that the scaling relations are steeper than that of the hot plasma, signaling kinetic energy losses and the presence of supersonic flows. In this work we use high-resolution simulations to explore the turbulent velocity structure of the cold filaments at the cores of galaxy clusters. Our results indicate that supersonic turbulent structures can be “frozen” in the cold gas that cools and fragments out of a fast, ∼107 K outflow driven by the central active galactic nucleus (AGN), when the radiative cooling time is shorter than the dynamical sound-crossing time. After the cold gas formation, however, the slope of the velocity structure function (VSF) flattens significantly over short, ∼10 Myr timescales. The lack of flattened VSF in observations of Hα filaments indicates that the Hα-emitting phase is short-lived for the cold gas in galaxy clusters. On the other hand, the ubiquity of supersonic turbulence revealed by observed filaments strongly suggests that supersonic outflows are an integral part of AGN–ICM interaction, and that AGN activity plays a crucial role at driving turbulence in galaxy clusters.
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Hu, Haojie, Yu Qiu, Marie-Lou Gendron-Marsolais, Tamara Bogdanović, Julie Hlavacek-Larrondo, Luis C. Ho, Kohei Inayoshi i Brian R. McNamara. "Signature of Supersonic Turbulence in Galaxy Clusters Revealed by AGN-driven Hα Filaments". Astrophysical Journal Letters 929, nr 2 (1.04.2022): L30. http://dx.doi.org/10.3847/2041-8213/ac6601.
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Abstract The hot intracluster medium (ICM) is thought to be quiescent with low observed velocity dispersions. Surface brightness fluctuations of the ICM also suggest that its turbulence is subsonic with a Kolmogorov scaling relation, indicating that the viscosity is suppressed and the kinetic energy cascades to small scales unscathed. However, recent observations of the cold gas filaments in galaxy clusters find that the scaling relations are steeper than that of the hot plasma, signaling kinetic energy losses and the presence of supersonic flows. In this work we use high-resolution simulations to explore the turbulent velocity structure of the cold filaments at the cores of galaxy clusters. Our results indicate that supersonic turbulent structures can be “frozen” in the cold gas that cools and fragments out of a fast, ∼107 K outflow driven by the central active galactic nucleus (AGN), when the radiative cooling time is shorter than the dynamical sound-crossing time. After the cold gas formation, however, the slope of the velocity structure function (VSF) flattens significantly over short, ∼10 Myr timescales. The lack of flattened VSF in observations of Hα filaments indicates that the Hα-emitting phase is short-lived for the cold gas in galaxy clusters. On the other hand, the ubiquity of supersonic turbulence revealed by observed filaments strongly suggests that supersonic outflows are an integral part of AGN–ICM interaction, and that AGN activity plays a crucial role at driving turbulence in galaxy clusters.
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Scannapieco, Evan, i Marcus Brüggen. "Subgrid Modeling of AGN‐driven Turbulence in Galaxy Clusters". Astrophysical Journal 686, nr 2 (20.10.2008): 927–47. http://dx.doi.org/10.1086/591228.
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Wang, C., M. Ruszkowski, C. Pfrommer, S. Peng Oh i H.-Y. K. Yang. "Non-Kolmogorov turbulence in multiphase intracluster medium driven by cold gas precipitation and AGN jets". Monthly Notices of the Royal Astronomical Society 504, nr 1 (8.04.2021): 898–909. http://dx.doi.org/10.1093/mnras/stab966.
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ABSTRACT Active galactic nuclei (AGNs) feedback is responsible for maintaining plasma in global thermal balance in extended haloes of elliptical galaxies and galaxy clusters. Local thermal instability in the hot gas leads to the formation of precipitating cold gas clouds that feed the central supermassive black holes, thus heating the hot gas and maintaining global thermal equilibrium. We perform 3D magnetohydrodynamical (MHD) simulations of self-regulated AGNs feedback in a Perseus-like galaxy cluster with the aim of understanding the impact of the feedback physics on the turbulence properties of the hot and cold phases of the intracluster medium (ICM). We find that, in general, the cold phase velocity structure function (VSF) is steeper than the prediction from Kolmogorov’s theory. We attribute the physical origin of the steeper slope of the cold phase VSF to the driving of turbulent motions primarily by the gravitational acceleration acting on the ballistic clouds. We demonstrate that, in the pure hydrodynamical case, the precipitating cold filaments may be the dominant agent driving turbulence in the hot ICM. The arguments in favour of this hypothesis are that: (i) the cold phase mass dominates over hot gas mass in the inner cool core; (ii) hot and cold gas velocities are spatially correlated; (iii) both the cold and hot phase velocity distributions are radially biased. We show that, in the MHD case, the turbulence in the ambient hot medium (excluding the jet cone regions) can also be driven by the AGN jets. The driving is then facilitated by enhanced coupling due to magnetic fields of the ambient gas and the AGN jets. In the MHD case, turbulence may thus be driven by a combination of AGN jet stirring and filament motions. We conclude that future observations, including those from high spatial and spectral resolution X-ray missions, may help to constrain self-regulated AGN feedback by quantifying the multitemperature VSF in the ICM.
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Guillard, P., F. Boulanger, M. D. Lehnert, G. Pineau des Forêts, F. Combes, E. Falgarone i J. Bernard-Salas. "Exceptional AGN-driven turbulence inhibits star formation in the 3C 326N radio galaxy". Astronomy & Astrophysics 574 (20.01.2015): A32. http://dx.doi.org/10.1051/0004-6361/201423612.
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Prasad, Deovrat, Prateek Sharma i Arif Babul. "Cool-core Clusters: The Role of BCG, Star Formation, and AGN-driven Turbulence". Astrophysical Journal 863, nr 1 (9.08.2018): 62. http://dx.doi.org/10.3847/1538-4357/aacce8.
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Olivares, V., Y. Su, W. Forman, M. Gaspari, F. Andrade-Santos, P. Salome, P. Nulsen, A. Edge, F. Combes i C. Jones. "X-Ray Cavity Dynamics and Their Role in the Gas Precipitation in Planck Sunyaev–Zeldovich (SZ) Selected Clusters". Astrophysical Journal 954, nr 1 (22.08.2023): 56. http://dx.doi.org/10.3847/1538-4357/ace359.
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Abstract We study active galactic nucleus (AGN) feedback in nearby (z < 0.35) galaxy clusters from the Planck Sunyaev–Zeldovich sample using Chandra observations. This nearly unbiased mass-selected sample includes both relaxed and disturbed clusters and may reflect the entire AGN feedback cycle. We find that relaxed clusters better follow the one-to-one relation of cavity power versus cooling luminosity, while disturbed clusters display higher cavity power for a given cooling luminosity, likely reflecting a difference in cooling and feedback efficiency. Disturbed clusters are also found to contain asymmetric cavities when compared to relaxed clusters, hinting toward the influence of the intracluster medium (ICM) “weather” on the distribution and morphology of the cavities. Disturbed clusters do not have fewer cavities than relaxed clusters, suggesting that cavities are difficult to disrupt. Thus, multiple cavities are a natural outcome of recurrent AGN outbursts. As in previous studies, we confirm that clusters with short central cooling times, t cool, and low central entropy values, K 0, contain warm ionized (10,000 K) or cold molecular (<100 K) gas, consistent with ICM cooling and a precipitation/chaotic cold accretion scenario. We analyzed archival Multi-Unit Spectroscopic Explorer observations that are available for 18 clusters. In 11/18 of the cases, the projected optical line emission filaments appear to be located beneath or around the cavity rims, indicating that AGN feedback plays an important role in forming the warm filaments by likely enhancing turbulence or uplift. In the remaining cases (7/18), the clusters either lack cavities or their association of filaments with cavities is vague, suggesting alternative turbulence-driven mechanisms (sloshing/mergers) or physical time delays are involved.
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Chen, Yi-Xian, Yan-Fei Jiang, Jeremy Goodman i Eve C. Ostriker. "3D Radiation Hydrodynamic Simulations of Gravitational Instability in AGN Accretion Disks: Effects of Radiation Pressure". Astrophysical Journal 948, nr 2 (1.05.2023): 120. http://dx.doi.org/10.3847/1538-4357/acc023.
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Abstract We perform 3D radiation hydrodynamic local shearing-box simulations to study the outcome of gravitational instability (GI) in optically thick active galactic nuclei (AGNs) accretion disks. GI develops when the Toomre parameter Q T ≲ 1, and may lead to turbulent heating that balances radiative cooling. However, when radiative cooling is too efficient, the disk may undergo runaway gravitational fragmentation. In the fully gas-pressure-dominated case, we confirm the classical result that such a thermal balance holds when the Shakura–Sunyaev viscosity parameter (α) due to the gravitationally driven turbulence is ≲0.2, corresponding to dimensionless cooling times Ωt cool ≳ 5. As the fraction of support by radiation pressure increases, the disk becomes more prone to fragmentation, with a reduced (increased) critical value of α (Ωt cool). The effect is already significant when the radiation pressure exceeds 10% of the gas pressure, while fully radiation-pressure-dominated disks fragment at t cool ≲ 50 Ω−1. The latter translates to a maximum turbulence level α ≲ 0.02, comparable to that generated by magnetorotational instability. Our results suggest that gravitationally unstable (Q T ∼ 1) outer regions of AGN disks with significant radiation pressure (likely for high/near-Eddington accretion rates) should always fragment into stars, and perhaps black holes.
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Heinrich, Andrew M., Yi-Hao Chen, Sebastian Heinz, Irina Zhuravleva i Eugene Churazov. "Constraining black hole feedback in galaxy clusters from X-ray power spectra". Monthly Notices of the Royal Astronomical Society 505, nr 3 (31.05.2021): 4646–54. http://dx.doi.org/10.1093/mnras/stab1557.
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ABSTRACT Jets launched by the supermassive black holes in the centres of cool-core clusters are the most likely heat source to solve the cooling flow problem. One way for this heating to occur is through generation of a turbulent cascade by jet-inflated bubbles. Measurements of the X-ray intensity power spectra show evidence of this cascade in different regions of the cluster, constraining the role of driving mechanisms. We analyse feedback simulations of the Perseus cluster to constrain the effect of the jet activity on the intensity fluctuations and kinematics of the cluster atmosphere. We find that, within the inner 60 kpc, the power spectra of the predicted surface brightness fluctuations are broadly consistent with those measured by Chandra and that even a single episode of jet activity can generate a long-lasting imprint on the intensity fluctuations in the innermost region of the cluster. Active galactic nucleus (AGN)-driven motions within the same region approach the values reported by Hitomi during and right after the AGN episode. However, the line-of-sight velocity dispersion excited by the jet in simulations underpredicts the Hitomi measurement. This indicates that driving a volume-filling sustained level of turbulence requires several episodes of jet activity, and/or additional processes drive turbulence outside the 60-kpc sphere. This also suggests that sharp edges of the bubbles in the innermost region of the cluster contribute substantially to the intensity of fluctuations, consistent with the Perseus observations in the inner 30-kpc region. We discuss new diagnostics to decompose annular power spectra to constrain past episodes of jet activity.
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Bambic, Christopher J., Brian J. Morsony i Christopher S. Reynolds. "Suppression of AGN-driven Turbulence by Magnetic Fields in a Magnetohydrodynamic Model of the Intracluster Medium". Astrophysical Journal 857, nr 2 (17.04.2018): 84. http://dx.doi.org/10.3847/1538-4357/aab558.
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Kretschmer, Michael, i Romain Teyssier. "Forming early-type galaxies without AGN feedback: a combination of merger-driven outflows and inefficient star formation". Monthly Notices of the Royal Astronomical Society 492, nr 1 (12.12.2019): 1385–98. http://dx.doi.org/10.1093/mnras/stz3495.
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ABSTRACT Regulating the available gas mass inside galaxies proceeds through a delicate balance between inflows and outflows, but also through the internal depletion of gas due to star formation. At the same time, stellar feedback is the internal engine that powers the strong outflows. Since star formation and stellar feedback are both small-scale phenomena, we need a realistic and predictive subgrid model for both. We describe the implementation of supernova momentum feedback and star formation based on the turbulence of the gas in the ramses code. For star formation, we adopt the so-called multifreefall model. The resulting star formation efficiencies can be significantly smaller or bigger than the traditionally chosen value of $1\, {\rm per\, cent}$. We apply these new numerical models to a prototype cosmological simulation of a massive halo that features a major merger which results in the formation of an early-type galaxy without using AGN feedback. We find that the feedback model provides the first-order mechanism for regulating the stellar and baryonic content in our simulated galaxy. At high redshift, the merger event pushes gas to large densities and large turbulent velocity dispersions, such that efficiencies come close to $10\, {\rm per\, cent}$, resulting in large star formation rate (SFR). We find small molecular gas depletion time during the starburst, in perfect agreement with observations. Furthermore, at late times, the galaxy becomes quiescent with efficiencies significantly smaller than $1\, {\rm per\, cent}$, resulting in small SFR and long molecular gas depletion time.
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Liao, Mai, Junxian Wang, Wenyong Kang i Minhua Zhou. "Exploring the connection between ultraviolet/optical variations and radio emission in radio-quiet quasars: clues about the origin of radio emission". Monthly Notices of the Royal Astronomical Society 512, nr 1 (15.03.2022): 296–303. http://dx.doi.org/10.1093/mnras/stac266.
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ABSTRACT Radio emission in radio-quiet quasars (RQQs) has long been a mystery and its physical origin remains unclear. In previous work, we have found that quasars that are more variable in ultraviolet (UV)/optical have stronger X-ray emission, indicating a link between disc turbulence and X-ray corona heating. In this work, for the first time, we investigate the relation between UV/optical variability and the radio emission in RQQs selected from the Sloan Digital Sky Survey Stripe 82 survey and the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey. We median stack the FIRST images and detect clear signals from RQQs in the co-added images of individually radio non-detected sources. Controlling the effects of other parameters, including redshift, black hole mass, bolometric luminosity and Eddington ratio, we find more variable RQQs, which are known to be relatively brighter in X-ray, and show tentatively weaker radio emission, contrary to the linear X-ray/radio correlation if the radio emission is from, or driven by, the corona. This discovery also suggests that if the radio emission in RQQs is driven by AGN activity (such as a weak jet), the underlying driving process is independent of the disc turbulence, which drives UV/optical variability and probably also corona heating. Alternatively, the radio emission could be a result of star formation in the host galaxies.
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Bourne, Martin A., Debora Sijacki i Ewald Puchwein. "AGN jet feedback on a moving mesh: lobe energetics and X-ray properties in a realistic cluster environment". Monthly Notices of the Royal Astronomical Society 490, nr 1 (26.09.2019): 343–49. http://dx.doi.org/10.1093/mnras/stz2604.
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ABSTRACT Jet feedback from active galactic nuclei (AGN) harboured by brightest cluster galaxies is expected to play a fundamental role in regulating cooling in the intracluster medium (ICM). While observations and theory suggest energy within jet lobes balances ICM radiative losses, the modus operandi of energy communication with the ICM remains unclear. We present simulations of very high resolution AGN-driven jets launching in a live, cosmological galaxy cluster, within the moving mesh code arepo. As the jet propagates through the ICM the majority of its energy, which is initially in the kinetic form, thermalizes quickly through internal shocks and inflates lobes of very hot gas. The jets effectively heat the cluster core, with PdV work and weather-aided mixing being the main channels of energy transfer from the lobes to the ICM, while strong shocks and turbulence are subdominant. We additionally present detailed mock X-ray maps at different stages of evolution, revealing clear cavities surrounded by X-ray bright rims, with lobes being detectable for up to ∼108 yr even when magnetic draping is ineffective. We find bulk motions in the cluster can significantly affect lobe propagation, offsetting them from the jet direction and imparting bulk velocities that can dominate over the buoyantly rising motion.
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Nesvadba, N. P. H., C. De Breuck, M. D. Lehnert, P. N. Best i C. Collet. "The SINFONI survey of powerful radio galaxies at z ~ 2: Jet-driven AGN feedback during the Quasar Era". Astronomy & Astrophysics 599 (marzec 2017): A123. http://dx.doi.org/10.1051/0004-6361/201528040.
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We present VLT/SINFONI imaging spectroscopy of the rest-frame optical emission lines of warm ionized gas in 33 powerful radio galaxies at redshifts z ≳ 2, which are excellent sites to study the interplay of rapidly accreting active galactic nuclei and the interstellar medium of the host galaxy in the very late formation stages of massive galaxies. Our targets span two orders of magnitude in radio size (2−400 kpc) and kinetic jet energy (a few 1046– almost 1048 erg s-1). All sources have complex gas kinematics with broad line widths up to ~1300 km s-1. About half have bipolar velocity fields with offsets up to 1500 km s-1 and are consistent with global back-to-back outflows. The others have complex velocity distributions, often with multiple abrupt velocity jumps far from the nucleus of the galaxy, and are not associated with a major merger in any obvious way. We present several empirical constraints that show why gas kinematics and radio jets seem to be physically related in all galaxies of the sample. The kinetic energy in the gas from large scale bulk and local outflow or turbulent motion corresponds to a few 10-3 to 10-2 of the kinetic energy output of the radio jet. In galaxies with radio jet power ≳ 1047 erg s-1, the kinetic energy in global back-to-back outflows dominates the total energy budget of the gas, suggesting that bulk motion of outflowing gas encompasses the global interstellar medium. This might be facilitated by the strong gas turbulence, as suggested by recent analytical work. We compare our findings with recent hydrodynamic simulations, and discuss the potential consequences for the subsequent evolution of massive galaxies at high redshift. Compared with recent models of metal enrichment in high-z AGN hosts, we find that the gas-phase metallicities in our galaxies are lower than in most low-z AGN, but nonetheless solar or even super-solar, suggesting that the ISM we see in these galaxies is very similar to the gas from which massive low-redshift galaxies formed most of their stars. This further highlights that we are seeing these galaxies near the end of their active formation phase.
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de Gouveia Dal Pino, E. M., D. Falceta-Gonçalves, J. S. Gallagher, C. Melioli, A. D'Ercole i F. Brighenti. "The role of SN-driven turbulence on the formation of outflows, inflows and cooling flows: from Galaxies to Clusters of Galaxies". Proceedings of the International Astronomical Union 5, H15 (listopad 2009): 452–53. http://dx.doi.org/10.1017/s1743921310010240.
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AbstractStar forming galaxies often exhibit hot halos with structures that resemble chimneys and fountains extending for several kpc above the galaxy. Observations indicate that they are probably produced by supernovae (SNe) which blow superbubbles that carve holes in the disk. Through these holes, high speed material is injected and expands buoyantly up to a maximum height and then returns to the disk pulled by the galaxy gravity. This circulating gas in a fountain tends to condense out forming high-velocity clouds and filaments. Starburst galaxies also show evidence that the spectacular winds that arise from their disk are fed by SNe explosions. Similarly, at galaxy cluster scales, most massive clusters exhibit rich filamentary structure of ionized gas which is distributed all around the central galaxy. We discuss here the role that SNe bubbles play in driving outflows and filamentary structures both at galaxy and galaxy-cluster scales. With the help of HD and MHD numerical simulations, we show in particular that SN-driven turbulence may play a key role at helping a central AGN halting and ”isotropize” the cooling flow in the central regions of a galaxy cluster.
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Scoville, Nick, Andreas Faisst, John Weaver, Sune Toft, Henry J. McCracken, Olivier Ilbert, Tanio Diaz-Santos i in. "Cosmic Evolution of Gas and Star Formation *". Astrophysical Journal 943, nr 2 (27.01.2023): 82. http://dx.doi.org/10.3847/1538-4357/aca1bc.
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Abstract Atacama Large Millimeter/submillimeter Array (ALMA) observations of the long-wavelength dust continuum are used to estimate the gas masses in a sample of 708 star-forming galaxies at z = 0.3−4.5. We determine the dependence of gas masses and star formation efficiencies (SFEs; SFR per unit gas mass) on redshift (z), M *, and star formation rate (SFR) relative to the main sequence (MS). We find that 70% of the increase in SFRs of the MS is due to the increased gas masses at earlier epochs, while 30% is due to increased efficiency of star formation (SF). For galaxies above the MS this is reversed—with 70% of the increased SFR relative to the MS being due to elevated SFEs. Thus, the major evolution of star formation activity at early epochs is driven by increased gas masses, while the starburst activity taking galaxies above the MS is due to enhanced triggering of star formation (likely due to galactic merging). The interstellar gas peaks at z = 2 and dominates the stellar mass down to z = 1.2. Accretion rates needed to maintain continuity of the MS evolution reach >100 M ⊙ yr−1 at z > 2. The galactic gas contents are likely the driving determinant for both the rise in SF and AGN activity from z = 5 to their peak at z = 2 and subsequent fall at lower z. We suggest that for self-gravitating clouds with supersonic turbulence, cloud collisions and the filamentary structure of the clouds regulate the star formation activity.
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Gammie, Charles F. "Nonlinear Outcome of Gravitational Instability in Optically Thick Disks". International Astronomical Union Colloquium 163 (1997): 704. http://dx.doi.org/10.1017/s0252921100043530.
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AbstractIn the outer parts of disks in active galactic nuclei and around young stellar objects (YSOs) the internal sources of heat may be too weak to prevent gravitational instability. We are thus motivated to examine the nonlinear outcome of gravitational instability in an optically thick disk. We use height-integrated, two-dimensional numerical simulations that include pressure (the gas has a polytropic equation of state), self-gravity, and cooling. The cooling function is calculated using a one-zone model and is characterized by a single dimensionless parameter τcool, which is the ratio of the cooling time to the orbital period. The simulations are done in the context of a local model of the disk (the “shearing sheet”). We also include the possibility of an effective “viscosity” characterized by a dimensionless parameter α.We find that the gravitational instability in thin, Keplerian disks leads to sustained angular momentum transport that is essentially local in character. Instability drives Q toward 1.7, and provides an angular momentum flux αeff ≃ 0.4/τcool. The disk breaks up when the cooling time is shorter than the dynamical time, which is equivalent to saying that αeff < 1. We conclude that gravitational instability can raise the angular momentum transport rate in the outer parts of AGN and YSO disks (although YSO disks may be too thick for our local approach to be strictly applicable). This can occur over a factor of a few in radius. The gravitationally dominated region is bounded on the inside by that radius where other heating processes (e.g. MHD turbulence driven by the Balbus-Hawley instability) make Q > 1. It is bounded on the outside by that radius where the cooling time is shorter than the dynamical time, or the disk is optically thin so that the equation of state is soft. At larger radius the disk will be clumpy.
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Wittor, D., i M. Gaspari. "Erratum: Dissecting the turbulent weather driven by mechanical AGN feedback". Monthly Notices of the Royal Astronomical Society 502, nr 4 (7.03.2021): 5854–55. http://dx.doi.org/10.1093/mnras/stab454.
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Wada, Keiichi. "Radiation-driven Feedback to the ISM around AGNs". Proceedings of the International Astronomical Union 8, S292 (sierpień 2012): 357–62. http://dx.doi.org/10.1017/s1743921313001695.
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AbstractAlthough the “donut-like” obscuring molecular torus is often postulated to explain the type-1 and -2 dichotomy in AGNs, its physical origin is still unclear. We propose a plausible mechanism to explain the formation of the geometrically and optically thick torus, i.e. radiation-driven fountain. Using 3-D hydrodynamic simulations including radiative feedback from the central source, taking into account the X-ray heating and radiation pressure on the gas, we found that a vertical circulation of gas is generated in the central few to tens parsecs. Interaction between the non-steady outflows and inflows causes the formation of a geometrically thick torus with internal turbulent motion. As a result, the AGN is obscured for a wide range of solid angles. In a quasi-steady state, the opening angles for the column density toward a black hole < 1023 cm−2 are approximately ± 30° and ± 50° for AGNs with 10% and 1% Eddington luminosity, respectively. Mass inflows through the torus coexist with the outflow and internal turbulent motion, although the average mass accretion rate to the central parsec region is about ten times smaller than the accretion rate required to maintain the assumed AGN luminosity. This implies that relatively luminous AGN activity is intrinsically intermittent or that there are other mechanisms, such as stellar energy feedback, that enhance the mass accretion to the center.
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Steinbring, Eric. "Direct Evidence for AGN-Driven Winds in a z = 1.5 Radio Galaxy". Proceedings of the International Astronomical Union 5, S267 (sierpień 2009): 407. http://dx.doi.org/10.1017/s1743921310006915.
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Feedback from AGN is a key component in most current models of galaxy formation and evolution. For the most massive galaxies, heating and removal of gas by the AGN could precipitate an abrupt quenching of star formation during a dramatic blow-out phase. The “smoking gun” for such a scenario would be direct evidence of powerful outflows associated with the jet. I present some preliminary results of a program to look for these in high-z radio galaxies (HzRGs). Recent observations of the z = 1.5 radio galaxy 3C 230 obtained with the NIFS integral-field spectrograph and Altair laser adaptive optics facility on Gemini North are shown. These reveal with unprecedented resolution the complex kinematics of this system in redshifted Hα and [N ii] emission. The bi-polar velocity field is aligned with the jet axis, with a kinematic center associated with the radio core itself, and turbulent edges approaching the galaxy's escape velocity. This suggests a gas mass of roughly 1011M⊙ has been propagating outwards for 107 to 108 years, corresponding to a mass loss of roughly 102–3M⊙ yr−1, based on its velocity and spatial extent. This is in good agreement with the energetics and typical ages of radio jets, and likely heralds the onset of the “red and dead” stage for this HzRG.
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Vidal-García, A., E. Falgarone, F. Arrigoni Battaia, B. Godard, R. J. Ivison, M. A. Zwaan, C. Herrera i in. "Where infall meets outflows: turbulent dissipation probed by CH+ and Lyα in the starburst/AGN galaxy group SMM J02399−0136 at z ∼ 2.8". Monthly Notices of the Royal Astronomical Society 506, nr 2 (27.05.2021): 2551–73. http://dx.doi.org/10.1093/mnras/stab1503.
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ABSTRACT We present a comparative analysis of the $\rm CH^+$(1–0) and Lyα lines, observed with the Atacama Large Millimeter Array and Keck telescope, respectively, in the field of the submillimetre-selected galaxy SMM J02399−0136 at z ∼ 2.8, which comprises a heavily obscured starburst galaxy and a broad absorption line quasar, immersed in a large Lyα nebula. This comparison highlights the critical role played by turbulence in channelling the energy across gas phases and scales, splitting the energy trail between hot/thermal and cool/turbulent phases in the circumgalactic medium (CGM). The unique chemical and spectroscopic properties of $\rm CH^+$ are used to infer the existence of a massive (∼3.5 × 1010 M⊙), highly turbulent reservoir of diffuse molecular gas of radius ∼20 kpc coinciding with the core of the Lyα nebula. The whole cool and cold CGM is shown to be inflowing towards the galaxies at a velocity ∼ 400 km s−1. Several kpc-scale shocks are detected tentatively in $\rm CH^+$ emission. Their linewidth and specific location in space and velocity with respect to the high-velocity Lyα emission suggest that they lie at the interface of the inflowing CGM and the high-velocity outflowing gas. They signpost the feeding of CGM turbulence by active galactic nuclei- and stellar-driven outflows. The mass and energy budgets of the CGM require net mass accretion at a rate commensurate with the star formation rate. From this similarity, we infer that the merger-driven burst of star formation and black-hole growth are ultimately fuelled by large-scale gas accretion.
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Talbot, Rosie Y., Martin A. Bourne i Debora Sijacki. "Blandford–Znajek jets in galaxy formation simulations: method and implementation". Monthly Notices of the Royal Astronomical Society 504, nr 3 (26.03.2021): 3619–50. http://dx.doi.org/10.1093/mnras/stab804.
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ABSTRACT Jets launched by active galactic nuclei (AGN) are believed to play a significant role in shaping the properties of galaxies and provide an energetically viable mechanism through which galaxies can become quenched. Here, we present a novel AGN feedback model, which we have incorporated into the arepo code, that evolves the black hole mass and spin as the accretion flow proceeds through a thin α-disc that we self-consistently couple to a Blandford–Znajek jet. We apply our model to the central region of a typical radio-loud Seyfert galaxy embedded in a hot circumgalactic medium (CGM). We find that jets launched into high-pressure environments thermalize efficiently due to the formation of recollimation shocks and the vigorous instabilities that these shocks excite increase the efficiency of the mixing of CGM and jet material. The beams of more overpressured jets, however, are not as readily disrupted by instabilities so the majority of the momentum flux at the jet base is retained out to the head, where the jet terminates in a reverse shock. All jets entrain a significant amount of cold circumnuclear disc material that, while energetically insignificant, dominates the lobe mass together with the hot, entrained CGM material. The jet power evolves significantly due to effective self-regulation by the black hole, fed by secularly driven, intermittent mass flows. The direction of jets launched directly into the circumnuclear disc changes considerably due to effective Bardeen–Petterson torquing. Interestingly, these jets obliterate the innermost regions of the disc and drive large-scale, multiphase, turbulent, bipolar outflows.
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Frias Castillo, Marta, Matus Rybak, Jacqueline Hodge, Paul van der Werf, Dominik A. Riechers, Daniel Vieira, Gabriela Calistro Rivera i in. "Kiloparsec-scale Imaging of the CO(1-0)-traced Cold Molecular Gas Reservoir in a z ∼ 3.4 Submillimeter Galaxy". Astrophysical Journal 930, nr 1 (1.05.2022): 35. http://dx.doi.org/10.3847/1538-4357/ac6105.
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Abstract We present a high-resolution study of the cold molecular gas as traced by CO(1-0) in the unlensed z ∼ 3.4 submillimeter galaxy SMM J13120+4242, using multiconfiguration observations with the Karl G. Jansky Very Large Array (JVLA). The gas reservoir, imaged on 0.″39 (∼3 kpc) scales, is resolved into two components separated by ∼11 kpc with a total extent of 16 ± 3 kpc. Despite the large spatial extent of the reservoir, the observations show a CO(1-0) FWHM linewidth of only 267 ± 64 km s−1. We derive a revised line luminosity of L CO ( 1 − 0 ) ′ = (10 ± 3) × 1010 K km s−1 pc2 and a molecular gas mass of M gas = (13 ± 3)× 1010 (α CO/1) M ⊙. Despite the presence of a velocity gradient (consistent with previous resolved CO(6-5) imaging), the CO(1-0) imaging shows evidence for significant turbulent motions that are preventing the gas from fully settling into a disk. The system likely represents a merger in an advanced stage. Although the dynamical mass is highly uncertain, we use it to place an upper limit on the CO-to-H2 mass conversion factor α CO of 1.4. We revisit the SED fitting, finding that this galaxy lies on the very massive end of the main sequence at z = 3.4. Based on the low gas fraction, short gas depletion time, and evidence for a central AGN, we propose that SMM J13120 is in a rapid transitional phase between a merger-driven starburst and an unobscured quasar. The case of SMM J13120 highlights how mergers may drive important physical changes in galaxies without pushing them off the main sequence.
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Faerman, Yakov, Viraj Pandya, Rachel S. Somerville i Amiel Sternberg. "Exploring the Milky Way Circumgalactic Medium in a Cosmological Context with a Semianalytic Model". Astrophysical Journal 928, nr 1 (1.03.2022): 37. http://dx.doi.org/10.3847/1538-4357/ac4ca6.
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Abstract We combine the Santa Cruz semianalytic model (SAM) for galaxy formation and evolution with the circumgalactic medium (CGM) model presented in Faerman et al. to explore the CGM properties of L * galaxies. We use the SAM to generate a sample of galaxies with halo masses similar to the Milky Way (MW) halo, M vir ≈ 1012 M ⊙, and find that the CGM mass and mean metallicity in the sample are correlated. We use the CGM masses and metallicities of the SAM galaxies as inputs for the FSM20 model and vary the amount of nonthermal support. The density profiles in our models can be approximated by power-law functions with slopes in the range of 0.75 < a n < 1.25, with higher nonthermal pressure resulting in flatter distributions. We explore how the gas pressure, dispersion measure, O VI–O VIII column densities, and cooling rates behave with the gas distribution and total mass. We show that for CGM masses below ∼3 × 1010 M ⊙ photoionization has a significant effect on the column densities of O VI and O VIII. The combination of different MW CGM observations favors models with similar fractions in thermal pressure, magnetic fields/cosmic rays, and turbulent support and with M CGM ∼ (3–10) × 1010 M ⊙. The MW O VI column requires t cool/t dyn ∼ 4, independent of the gas distribution. The AGN jet-driven heating rates in the SAM are enough to offset the CGM cooling, although exact balance is not required in star-forming galaxies. We provide predictions for the column densities of additional metal ions—N V, Ne VIII, and Mg X.
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Bogovalov, Sergey. "Physics of “Cold” Disk Accretion onto Black Holes Driven by Magnetized Winds". Galaxies 7, nr 1 (14.01.2019): 18. http://dx.doi.org/10.3390/galaxies7010018.
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Disk accretion onto black holes is accompanied by collimated outflows (jets). In active galactic nuclei (AGN), the kinetic energy flux of the jet (jet power or kinetic luminosity) may exceed the bolometric luminosity of the disk by a few orders of magnitude. This may be explained in the framework of the so called “cold” disk accretion. In this regime of accretion, the disk is radiatively inefficient because practically all the energy released at the accretion is carried out by the magnetized wind. This wind also provides efficient loss of the angular momentum by the matter in the disk. In this review, the physics of the accretion driven by the wind is considered from first principles. It is shown that the magnetized wind can efficiently carry out angular momentum and energy of the matter of the disk. The conditions when this process dominates conventional loss of the angular momentum due to turbulent viscosity are discussed. The “cold” accretion occurs when the viscous stresses in the disk can be neglected in comparison with impact of the wind on the accretion. Two problems crucial for survival of the model of “cold” accretion are considered. The first one is existence of the magnetohydrodynamical solutions for disk accretion purely due to the angular momentum loss by the wind. Another problem is the ability of the model to reproduce observations which demonstrate existence of the sources with kinetic power of jets 2–3 orders of magnitude exceeding the bolometric luminosity of disks. The solutions of the problem in similar prescriptions and numerical solutions without such an assumption are discussed. Calculations of the “unavoidable” radiation from the “cold” disk and the ratio of the jet power of the SMBH to the bolometric luminosity of the accretion disk around a super massive black hole are given in the framework of the Shakura and Sunyaev paradigm of an optically thick α -disk. The exploration of the Fundamental Plane of Black Holes allows us to obtain semi empirical equations that determine the bolometric luminosity and the ratio of the luminosities as functions of the black hole mass and accretion rate.
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Yokosawa, M. "Dynamical Evolution of Accretion Flow onto a Black Hole". Symposium - International Astronomical Union 188 (1998): 455–56. http://dx.doi.org/10.1017/s0074180900116006.
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Active galactic nuclei(AGN) produce many type of active phenomena, powerful X-ray emission, UV hump, narrow beam ejection, gamma-ray emission. Energy of these phenomena is thought to be brought out binding energy between a black hole and surrounding matter. What condition around a black hole produces many type of active phenomena? We investigated dynamical evolution of accretion flow onto a black hole by using a general-relativistic, hydrodynamic code which contains a viscosity based on the alpha-model. We find three types of flow's pattern, depending on thickness of accretion disk. In a case of the thin disk with a thickness less than the radius of the event horizon at the vicinity of a marginally stable orbit, the accreting flow through a surface of the marginally stable orbit becomes thinner due to additional cooling caused by a general-relativistic Roche-lobe overflow and horizontal advection of heat. An accretion disk with a middle thickness, 2rh≤h≤ 3rh, divides into two flows: the upper region of the accreting flow expands into the atmosphere of the black hole, and the inner region of the flow becomes thinner, smoothly accreting onto the black hole. The expansion of the flow generates a dynamically violent structure around the event horizon. The kinetic energy of the violent motion becomes equivalent to the thermal energy of the accreting disk. The shock heating due to violent motion produces a thermally driven wind which flows through the atmosphere above the accretion disk. A very thick disk, 4rh≤h,forms a narrow beam whose energy is largely supplied from hot region generated by shock wave. The accretion flowing through the thick disk,h≥ 2rh, cannot only form a single, laminar flow falling into the black hole, but also produces turbulent-like structure above the event horizon. The middle disk may possibly emit the X-ray radiation observed in active galactic nuclei. The thin disk may produce UV hump of Seyfert galaxy. Thick disk may produce a jet observed in radio galaxy. The thickness of the disk is determined by accretion rate, such ashκ κes/cṁf(r) κ 10rhṁf(r), at the inner region of the disk where the radiation pressure dominates over the gas pressure. Here, Ṁ is the accretion rate and ṁ is the normarized one by the critical-mass flux of the Eddington limit. κesandcare the opacity by electron scattering and the velocity of light.f(r) is a function with a value of unity far from the hole.
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Wittor, Denis, i Massimo Gaspari. "Unraveling Baroclinicity in Black Hole Weather Storms". Monthly Notices of the Royal Astronomical Society: Letters, 27.02.2023. http://dx.doi.org/10.1093/mnrasl/slad028.
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Abstract In the intracluster, intragroup, and circumgalactic medium (ICM, IGrM, CGM), turbulence plays a vital role in the self-regulated feedback and feeding cycle of central supermassive black holes (SMBHs). Here we continue our systematic dissection of the turbulent ‘weather’ in high-resolution hydrodynamical simulations of feedback driven by active galactic nuclei (AGN). In non-barotropic and stratified atmospheres, baroclinicity is expected to generate fresh turbulence via misaligned gradients of density and pressure – such as in cyclonic storms on Earth. In this work, we dissect for the first time baroclinicity and its components in the astrophysical halo weather. Over the macro-scale galaxy cluster, baroclinicity tends to be dynamically subdominant for the enstrophy amplification. However, at and below the meso scale near the SMBH (r < 10 kpc; t < 20 Myr), baroclinicity is important to seed the initial enstrophy during active periods of AGN jet feedback. We find that baroclinicity shows stronger correlation with the density rather than pressure gradients. Despite the density-pressure gradient misalignment being often below 45○, their amplitudes boosted by mechanical AGN feedback are sufficient to enable key enstrophy/turbulence generation. Our study provides a novel step forward in understanding astrophysical atmospheres toward a unified BlackHoleWeather framework, akin to the complexity of Earth’s weather.
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Heinrich, Andrew Mark, Yi-Hao Chen, Sebastian Heinz, Irina Zhuravleva i Eugene Churazov. "Constraining simulated black hole feedback in the Perseus Cluster". Proceedings of the Wisconsin Space Conference 1, nr 1 (25.02.2022). http://dx.doi.org/10.17307/wsc.v1i1.342.
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Active galactic nuclei in galaxy clusters can produce tightly collimated jets that inject energy into the surrounding intracluster medium (ICM). This feedback process can offset cooling losses from X-ray radiation that otherwise would result in cooling flow structures. Jet-inflated bubbles can heat the cluster via a turbulent cascade. The density fluctuation spectrum inferred from X-ray maps of the cluster shows different levels and scales of turbulence in different regions of the clusters, and can be used to determine the contribution of different driving mechanisms. By applying observational power spectrum techniques to synthetic X-ray data from feedback simulations of the Perseus cluster, we find that the density fluctuation spectra produced by a single episode of jet activity are broadly consistent with analysis of Chandra observations inside 60 kpc. The velocity dispersion effected by the AGN approaches Hitomi's measurement of turbulence in Perseus during the AGN episode, but is underpredicted later in the simulation. A fully established volume-filling turbulent cascade therefore requres multiple periods of jet activity, along with turbulence driven by other processes outside of the inner 60 kpc core. This also suggests the X-ray fluctuations directly associated with the jet bubble substantially contribute to the overall density fluctuation spectrum.
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Kempski, Philipp, Eliot Quataert i Jonathan Squire. "A new buoyancy instability in galaxy clusters due to streaming cosmic rays". Monthly Notices of the Royal Astronomical Society, 22.06.2023. http://dx.doi.org/10.1093/mnras/stad1744.
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Abstract Active Galactic Nuclei (AGN) are believed to provide the energy that prevents runaway cooling of gas in the cores of galaxy clusters. However, how this energy is transported and thermalized throughout the Intracluster Medium (ICM) remains unclear. In recent work we showed that streaming cosmic rays (CRs) destabilise sound waves in dilute ICM plasmas. Here we show that CR streaming in the presence of gravity also destabilises a pressure-balanced wave. We term this new instability the CR buoyancy instability (CRBI). In stark contrast to standard results without CRs, the pressure-balanced mode is highly compressible at short wavelengths due to CR streaming. Maximal growth rates are of order (pc/pg)β1/2ωff, where pc/pg is the ratio of CR pressure to thermal gas pressure, β is the ratio of thermal to magnetic pressure and ωff is the free-fall frequency. The CRBI operates alongside buoyancy instabilities driven by background heat fluxes, i.e. the heat-flux-driven buoyancy instability (HBI) and the magneto-thermal instability (MTI). When the thermal mean free path lmfp is ≪ the gas scale height H, the HBI/MTI set the growth rate on large scales, while the CRBI sets the growth rate on small scales. Conversely, when lmfp ∼ H and (pc/pg)β1/2 ≳ 1, CRBI growth rates exceed HBI/MTI growth rates even on large scales. Our results suggest that CR-driven instabilities may be partially responsible for the sound waves/weak shocks and turbulence observed in galaxy clusters. CR-driven instabilities generated near radio bubbles may also play an important role redistributing AGN energy throughout clusters.
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Liska, M., C. Hesp, A. Tchekhovskoy, A. Ingram, M. van der Klis, S. B. Markoff i M. Van Moer. "Disc Tearing and Bardeen-Petterson Alignment in GRMHD Simulations of Highly Tilted Thin Accretion Discs". Monthly Notices of the Royal Astronomical Society, 20.03.2020. http://dx.doi.org/10.1093/mnras/staa099.
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Abstract Luminous active galactic nuclei (AGN) and X-Ray binaries (XRBs) often contain geometrically thin, radiatively cooled accretion discs. According to theory, these are – in many cases – initially highly misaligned with the black hole equator. In this work, we present the first general relativistic magnetohydrodynamic simulations of very thin (h/r∼0.015-0.05) accretion discs around rapidly spinning (a∼0.9) black holes and tilted by 45-65 degrees. We show that the inner regions of the discs with h/r≲0.03 align with the black hole equator, though out to smaller radii than predicted by analytic work. The inner aligned and outer misaligned disc regions are separated by a sharp break in tilt angle accompanied by a sharp drop in density. We find that frame-dragging by the spinning black hole overpowers the disc viscosity, which is self-consistently produced by magnetized turbulence, tearing the disc apart and forming a rapidly precessing inner sub-disc surrounded by a slowly precessing outer sub-disc. We find that the system produces a pair of relativistic jets for all initial tilt values. At small distances the black hole launched jets precess rapidly together with the inner sub-disc, whereas at large distances they partially align with the outer sub-disc and precess more slowly. If the tearing radius can be modeled accurately in future work, emission model independent measurements of black hole spin based on precession-driven quasi-periodic oscillations may become possible.