2025-09-30 オークリッジ国立研究所（ORNL）
Supermassive black holes constantly pump dust, gas and heat into their environments, creating accretion disks like this one. Simulations on ORNL’s Frontier supercomputer offer the clearest portrait yet of how galaxies regulate this energy over billions of years. Credit: Brian O’Shea, Michigan State
＜関連情報＞
- https://www.ornl.gov/news/frontier-simulations-pierce-mysteries-galactic-nuclei
- https://iopscience.iop.org/article/10.3847/1538-4357/adde45
- https://www.aanda.org/articles/aa/full_html/2025/06/aa54278-25/aa54278-25.html
- https://www.aanda.org/articles/aa/full_html/2024/11/aa51031-24/aa51031-24.html
銀河群および銀河団におけるSMBHフィードバックのXMAGNETエクサスケールMHDシミュレーション：概要と予備的な銀河団結果 The XMAGNET Exascale MHD Simulations of SMBH Feedback in Galaxy Groups and Clusters: Overview and Preliminary Cluster Results
Philipp Grete, Brian W. O’Shea, Forrest W. Glines, Deovrat Prasad, Benjamin D. Wibking, Martin Fournier, Marcus Brüggen, and G. Mark Voit
The Astrophysical Journal Published: 2025 July 21
DOI:10.3847/1538-4357/adde45
Abstract
We present initial results from extremely well-resolved 3D magnetohydrodynamical simulations of idealized galaxy clusters, conducted using the AthenaPK code on the Frontier exascale supercomputer. These simulations explore the self-regulation of galaxy groups and cool-core clusters by cold gas-triggered active galactic nucleus (AGN) feedback incorporating magnetized kinetic jets. Our simulation campaign includes simulations of galaxy groups and clusters with a range of masses and intragroup and intracluster medium properties. In this paper, we present results that focus on a Perseus-like cluster. We find that the simulated clusters are self-regulating, with the cluster cores staying at a roughly constant thermodynamic state and AGN jet power staying at physically reasonable values (≃1044–1045 erg s–1) for billions of years without a discernible duty cycle. These simulations also produce significant amounts of cold gas, with calculations having strong magnetic fields generally both promoting cold gas formation and allowing cold gas out to much larger cluster-centric radii (≃100 kpc) than simulations with weak or no fields (≃10 kpc), and also having more filamentary cold gas morphology. We find that AGN feedback significantly increases the strength of magnetic fields at the center of the cluster. We also find that the magnetized turbulence generated by the AGN results in turbulence where the velocity power spectra are tied to AGN activity, whereas the magnetic energy spectra are much less impacted after reaching a stationary state.
XMAGNET: 多相銀河間媒質における活動銀河核駆動乱流の速度構造関数 XMAGNET: Velocity structure functions of active galactic nucleus-driven turbulence in the multiphase intracluster medium
M. Fournier, P. Grete, M. Brüggen, B. W. O’Shea, D. Prasad, B. D. Wibking, F. W. Glines and R. Mohapatra
Astronomy & Astrophysics Published:03 June 2025
DOI:https://doi.org/10.1051/0004-6361/202554278
Abstract
Context. Significant theoretical and observational efforts are underway to investigate the properties of the turbulence in the hot plasma that pervades galaxy clusters. Spectroscopy has been used to study the projected line-of-sight velocities in both the hot intracluster medium and the cold gas phase in combination with optical and X-ray telescopes.
Aims. In this work, we characterize the velocity structure functions (VSFs) of the multiphase intracluster medium in a simulated galaxy cluster core and study the effects of projections on the hot and cold phase of the gas.
Methods. We used the fiducial run of the XMAGNET suite, a collection of exascale magneto-hydrodynamical simulations of a cool-core cluster, to compute VSFs. The simulation includes radiative cooling as well as a model for active galactic nuclei feedback.
Results. Examining three-dimensional and line-of-sight VSFs, we find no clear correlation between the behavior of the hot (106 K ≤ T ≤ 108 K) and cold (T ≤ 105 K) phase VSFs. Assuming a power-law model for the VSF, we find that the power-law index m of the cold phase varies significantly throughout the 4 Gyr simulation time. We compared our VSFs with observations using mock optical and X-ray images, and we conclude that projection effects significantly impact the amplitude and power-law index of both the hot and cold phases. In the cold phase, applying a Gaussian smoothing filter to model effects of atmospheric seeing significantly increases the index of the projected VSF at scales below the filter’s kernel size. Moreover, the VSF amplitude and power-law index vary significantly depending on the viewing orientation.
Conclusions. Observational biases such as projection effects, atmospheric seeing, and the viewing angle cannot be ignored when interpreting the line-of-sight velocity structure of the intracluster medium.
冷核銀河団における磁化された冷たいフィラメントの特性 The properties of magnetised cold filaments in a cool-core galaxy cluster
M. Fournier, P. Grete, M. Brüggen, F. W. Glines and B. W. O’Shea
Astronomy & Astrophysics Published:19 November 2024
DOI:https://doi.org/10.1051/0004-6361/202451031
Abstract
Context. Filaments of cold gas (T ≤ 104 K) are found in the inner regions of many cool-core clusters. These structures are thought to play a major role in the regulation of feedback from active galactic nuclei (AGNs).
Aims. We study the morphology of the filaments, their formation, and their impact on the propagation of the outflowing AGN jets.
Methods. We present a set of GPU-accelerated 3D magnetohydrodynamic simulations of an idealised Perseus-like cluster using the performance portable code ATHENAPK. We include radiative cooling and a self-regulated AGN feedback model that redistributes accreted material through kinetic, thermal, and magnetic feedback.
Results We confirm that magnetic fields play an important role in both the formation and evolution of the cold material. These suppress the formation of massive cold discs and favour magnetically supported filaments over clumpy structures. Achieving resolutions of 25 − 50 pc, we find that filaments are not monolithic as they contain numerous and complex magnetically supported sub-structures. We find that the mass distribution of these clumps follows a power law of slope of ∼ − 0.6 for all investigated filaments. Studying the evolution of individual filaments, we find that their formation pathways can be diverse. We find examples of filaments forming through a combination of gas uplifting and condensation, as well as systems of purely infalling clumps condensing out of the intracluster medium. The density contrast between the cold gas and the outflowing hot material leads to recurring deflections of the jets, favouring inflation of bubbles.
Conslusions. Filaments in cool-core clusters are clumpy and contain numerous sub-structures, resulting from a complex interplay between magnetic fields, thermal instability, and jet-cloud interaction. Frequent deflections of the AGN outflows suppress jet collimation and favour the formation of large X-ray bubbles, and smaller off-axis cavities.
