Program
Monday – 20 July
8:15 – 9:00
Welcome Coffee & Registration
9:00 – 9:10
Opening Remarks
Norbert Werner | Masaryk UniversityAbstract ⓘ
TBA
9:10 – 9:35
Recent updates on ICM turbulence
Irina Zhuravleva | U ChicagoAbstract ⓘ
TBA
9:35 – 10:00
Probing ICM Turbulence with XRISM: Comparisons with Cosmological Simulations
Nhut Truong | NASA GSFC/UMDAbstract ⓘ
XRISM has recently delivered high-precision measurements of gas motions across multiple galaxy clusters, opening a new window for studying turbulence generation and dissipation in the ICM and enabling direct comparisons with modern numerical models. I will present a systematic comparison between XRISM kinematic measurements of clusters observed during the PV and GO phases and predictions from three state-of-the-art cosmological simulation suites (TNG-Cluster, The Three Hundred GADGET-X, and GIZMO-SIMBA), which implement distinct SMBH feedback prescriptions. By contrasting observed line-of-sight velocity dispersions and inferred kinetic pressure support with simulation predictions across different cluster types (cool-core versus non-cool-core) and spatial regions, I will discuss potential constraints on the modeling of gas motions, turbulence, and feedback processes in galaxy clusters. I will also discuss follow-up theoretical investigations of the ICM velocity power spectrum and their implication for interpreting XRISM measurements.
10:00 – 10:25
ICM Yesterday, Today and Tomorrow: turbulence, multi-phase cellularisation, nonthermal equilibria, and all that
Alex Schekochihin | University of OxfordAbstract ⓘ
TBA
10:25 – 11:10
Coffee Break
11:10 – 11:35
Galaxy motion and Gas Dynamics in Cooling Cluster Centres
Brian McNamara | Waterloo Centre for Astrophysics, University of WaterlooAbstract ⓘ
TBA
11:35 – 12:00
Rotation, Inflows, Outflows, and Turbulence in Hot Atmospheres from Galaxies to Galaxy Clusters
John ZuHone | Center for Astrophysics | Harvard & SmithsonianAbstract ⓘ
TBA
12:00 – 12:25
The role of active galactic nucleus (AGN) jet feedback and cosmological assembly on cool-core cluster entropy and turbulence
Rainer Weinberger | Leibniz-Institute for Astrophysics Potsdam (AIP)Abstract ⓘ
Cosmological assembly, radiative cooling, and AGN jet heating are key factors influencing intra-cluster medium (ICM) energetics in cool-core galaxy clusters. I will present recent isolated and cosmological hydrdodynamical simulations to clarify these process’s effect on the ICM. I will show that an analytic model of a heating-cooling equilibrium is able to predict the central entropy, and argue that this equilibrium entropy being too high might be the reason why many cosmological simulations struggle to produce low enough central entropies. Being able to reliably produce desired thermodynamic profiles, I will present a comparison between isolated and cosmological zoom simulations to study the impact of cosmological infall on the degree of turbulence in the cluster, as opposed to AGN jet activity. Finally, I will discuss warm ionized gas in these and future simulations.
12:25 – 12:40
Poster talks
Probing ICM turbulence with MHD exascale simulations
Martin Fournier | Hamburg UniversitatAbstract ⓘ
TBA
Resolving AGN Feedback in Cluster Cores with XRISM and Chandra
Hannah McCall | University of ChicagoAbstract ⓘ
TBA
12:40 – 14:00
Lunch
14:00 – 14:25
XRISM observations and simulations of the Perseus Cluster (tentative)
Congyao Zhang | Masaryk UniversityAbstract ⓘ
TBA
14:25 – 14:50
Disentangling AGN Feedback and Sloshing in the Perseus Cluster with XRISM: Insights from Idealized Simulations
Elena Bellomi | Center for Astrophysics | Harvard & SmithsonianAbstract ⓘ
TBA
14:50 – 15:15
Effects of ICM Turbulence on Magnetic Flux and Polarization Properties
Hui Li | Los Alamos National LaboratoryAbstract ⓘ
We have carried out 3D MHD simulations of evolution of jets and lobes in turbulent ICM to investigate how the ICM turbulence will affect their propagation and long-term properties. We investigate how the evolution and properties of magnetic fluxes during the jet/lobe stage, and the long-term fossil stage. We discuss how the implications for Faraday Rotation Measurements and compare them with observations, including polarizations.
15:15 – 16:00
Coffee Break
16:00 – 16:45
Discussion
16:45 – 17:45
Flash poster talks
17:45 – 20:00
Welcome Reception
Tuesday – 21 July
9:00 – 9:25
XRISM observations of the splash beneath the radio bubble in Ophiuchus
Helen Russell | University of NottinghamAbstract ⓘ
The X-ray Imaging and Spectroscopy Mission (XRISM) was launched by JAXA and NASA in late 2023. XRISM carries onboard the next generation of X-ray instrumentation - the microcalorimeter. With nearly two orders of magnitude improvement in spectral resolution over CCD spectroscopy, XRISM is now revealing the dynamics of hot atmospheres in massive galaxies and galaxy clusters. By mapping vast gas flows in these systems, XRISM will uncover how outbursts from supermassive black holes heat and eject the surrounding gas, and can thereby suppress star formation and slow galaxy growth. I will present new XRISM observations of the gas flows beneath the largest radio bubble on the sky in the Ophiuchus cluster. We detect bulk motion and an increase in velocity dispersion in the wake that are consistent with the uplift or splash expected beneath a buoyant radio bubble. Despite the vast power of this giant bubble, we show that the turbulent heating rate appears to fall far short of the ICM cooling losses.
9:25 – 9:50
Insights from simulations -- cool-core destruction and roles of turbulence
Hsiang-Yi Karen Yang | National Tsing Hua UniversityAbstract ⓘ
TBA
9:50 – 10:15
Lessons from TNG-Cluster: from cool cores, cavities and shocks to the interpretation of XRISM observations
Annalisa Pillepich | Max Planck Institute for Astronomy, HeidelbergAbstract ⓘ
TBA
10:15 – 11:10
Coffee Break
11:10 – 11:35
Multiphase AGN Feedback in Clusters of Galaxies as seen by JWST
Julie Hlavacek-Larrondo | Université de MontréalAbstract ⓘ
The best place to study radio-mode AGN feedback is in the hot atmospheres of galaxy clusters, which host the most massive black holes and where we can directly image their impact on the surrounding medium. At cluster centers, supermassive black holes launch powerful relativistic jets that inject vast amounts of energy through shock fronts, sound waves, turbulence, and molecular outflows. In this talk, I will present novel multi-wavelength observations that, for the first time, allow us to trace the entire radio-mode feedback cycle—from heating, to cooling, to feeding, and across scales from kiloparsecs down to parsecs. First, I will present new JWST observations of the archetypal Centaurus cluster, where NIRSpec/IFU data reveal a rotating circumnuclear disk directly connected to the surrounding filament network. This structure provides the long-sought missing link that channels gas from kiloparsec to 100-pc scales and ultimately into the central black hole, effectively closing the feedback loop. I will then place these results in a broader context using the Perseus cluster, where the combination of JWST with state-of-the-art XRISM and SITELLE/IFU observations allows us to map the full multiphase feedback cycle. In this system, I will show that the hot X-ray–emitting gas is deeply intertwined with the cold and warm nebular components, demonstrating that AGN feedback is inherently multiphase and dynamically complex. Together, these findings shed new light on the fundamental mechanisms that drive galaxy evolution, particularly supermassive black hole fueling/feedback and its intricate interplay with the host galaxy.
11:35 – 12:00
Magnetohydrodynamic Precipitation
Mark Voit | Michigan State UniversityAbstract ⓘ
Circumgalactic gas around massive galaxies generally has a volume-filling component—an atmosphere—with a temperature determined by the potential-well depth of the galaxy’s halo. If the atmosphere is near hydrostatic equilibrium and is stable to convection, then it can remain nearly homogeneous, as long as it is not too dense. But if its density is great enough, it becomes prone to producing a rain of cold clouds that fall toward the galaxy’s center and accrete onto its central black hole. My talk will explore how relatively weak magnetic fields enhance a galactic atmosphere’s tendency to produce cold clouds and how the cold gas becomes organized into vertically elongated, highly magnetized filaments that descend at sub-Keplerian speeds.
12:00 – 12:25
Journey to the Black Hole: Multiphase Accretion Flows From Galaxy Scales to Accretion Disk Scales
Yuan Li | UMass AmherstAbstract ⓘ
The feeding and feedback cycles of Supermassive black holes (SMBHs) play a vital role in regulating the intra-cluster medium in cluster centers. While state-of-the-art numerical simulations effectively reproduce multiphase gas at the galaxy scale, understanding its connection to the gas at the accretion-disk scale remains challenging. My group recently conducted numerical studies to bridge this gap. We use the Athena++ code to simulate an idealized elliptical galaxy based on M87 in the center of the Virgo Cluster. Our galaxy-scale simulations include a black hole jet feedback prescription that balances cooling on large scales. We construct mesoscale simulations to model the dynamical evolution of multiphase accretion flow within the central parsecs down to tens of gravitational radii of the SMBH. We find that the average accretion rate follows a simple scaling of $\dot{M} \propto r^{1/2}$ across seven orders of magnitude in scale, consistent with what has been found in single-phase accretion flows. While the cool clouds usually appear clumpy and amorphous on galaxy scales, at the mesoscale, the multiphase accretion flow typically settles to a disk, which is often connected to a misaligned disk on even smaller scales. At its highest resolution, our simulation can effectively model the black hole variability over a year-long timescale, which allows for direct comparison with current and future observations. These simulations will ultimately provide more realistic boundary and initial conditions for future general-relativistic magneto-hydrodynamical (GRMHD) simulations of the accretion disk, as well as better subgrid models for next-generation cosmological simulations.
12:25 – 12:40
Poster talks
The evolving ICM: XRISM insights into kinematic and non-equilibrium physics in merging clusters
Annie Heinrich | University of ChicagoAbstract ⓘ
TBA
AGN feedback as a driver of spiral-like gas structures and cold fronts in cool-core clusters
Majidul Rahaman | National Tsing Hua University, TaiwanAbstract ⓘ
Spiral features and cold fronts in cool-core (CC) galaxy clusters are among the most striking signatures of intracluster medium (ICM) dynamics, and are almost always interpreted as the result of minor merger-induced gas sloshing. Here, we show that AGN feedback alone can produce the same structures, without any external perturbation. Using three-dimensional cosmic-ray magnetohydrodynamic (CR-MHD) simulations of a Perseus-like cluster, we find that precessing, CR-dominated jets naturally drive spiral-like structures extending to ~150 kpc and accompanying cold fronts, through the coherent fallback of jet-uplifted gas during AGN quiescent phases. Comparing against XRISM/Resolve observations of Perseus, we find that while an off-axis merger broadly reproduces the large-scale velocity gradients, it falls short in the central ~30 kpc, a region where AGN-driven motions appear to dominate. We further show that during quiescent phases, both the velocity and magnetic fields develop an episodic, centrally confined tangential bias that stabilises cold fronts against Kelvin–Helmholtz instabilities. This behaviour is physically distinct from the more persistent, spatially extended tangential bias seen in merger simulations, and points to AGN feedback as the dominant driver of ICM structure in the innermost cluster core.
12:40 – 14:00
Lunch
14:00 – 14:25
Thermodynamic Imprints of AGN Feedback and the Baryon Cycle in eROSITA Galaxy Groups and Clusters
Esra Bulbul | Max Planck Institute for Extraterrestrial PhysicsAbstract ⓘ
TBA
14:25 – 14:50
Bridging Scales: Coupling the galactic nucleus to the larger cosmic environment
Kung-Yi Su | CIERA, Northwestern UniversityAbstract ⓘ
TBA
14:50 – 15:15
Heating from jets in cool-core galaxy clusters
Meenakshi M | Leibniz Institute for Astrophysics, PotsdamAbstract ⓘ
TBA
15:15 – 16:00
Coffee Break
16:00 – 16:25
Warm dusty molecular gas: disks, flows, filaments
Megan Donahue | Michigan State UniversityAbstract ⓘ
I will show preliminary results from our JWST mid-infrared and near-infrared campaign to obtain IFU observations of infrared emission from 6 relatively nearby brightest cluster galaxies in cool core clusters. This work significantly expands upon the Spitzer Infrared Spectroscopy of a similar set of galaxies by Donahue et al. 2011 which showed extraordinarily luminous rotationally-excited molecular hydrogen lines and PAH/dust emission. The Spitzer spectroscopy showed that the molecular hydrogen emission was unlikely to be powered by star formation. The JWST spectroscopy allows to measure and map gas velocities, line widths, and line fluxes and ratios at a resolution of less than 0.2".
16:25 – 16:50
Can Mixing Layer simulations explain the remarkably constant Hα–X-ray flux ratios in Galaxy Clusters?
Rajsekhar Mohapatra | Princeton UniversityAbstract ⓘ
TBA
16:50 – 17:15
Cosmic Rays and Thermal Instability in Cool Core Clusters
Mateusz Ruszkowski | University of Michigan in Ann ArborAbstract ⓘ
TBA
17:15 – 18:00
Discussion
Wednesday – 22 July
9:00 – 9:25
Unexpected radio halos
Reinout van Weeren | Leiden UniversityAbstract ⓘ
Diffuse radio emission in galaxy clusters, in the form of giant radio halos and mini-halos, provides unique insight into the interplay between cosmic rays, turbulence, and the thermal intracluster medium. Traditionally, giant halos are associated with merging clusters, while mini-halos are linked to cool-core systems. However, recent observations suggest that the distinction between these classes is less clear-cut than previously thought.
I will present MeerKAT and LOFAR observations of clusters exhibiting complex, multi-component diffuse radio emission that challenges the classical view that giant halos arise exclusively in merging systems without cool cores. Together with other recent discoveries, these results point toward a more diverse population of cluster radio halos than previously recognized. They also highlight potential observational biases and sensitivity limitations in earlier radio studies that may have led to extended halos being overlooked.
I will present MeerKAT and LOFAR observations of clusters exhibiting complex, multi-component diffuse radio emission that challenges the classical view that giant halos arise exclusively in merging systems without cool cores. Together with other recent discoveries, these results point toward a more diverse population of cluster radio halos than previously recognized. They also highlight potential observational biases and sensitivity limitations in earlier radio studies that may have led to extended halos being overlooked.
9:25 – 9:50
Lighting up the past: Odd Radio Circles as Tracers of Past Jet activity
Sebastian Heinz | University of Wisconsin-MadisonAbstract ⓘ
The recent discovery of odd radio circles (ORCs)--faint, roughly ring-like diffuse radio sources with radii of hundreds of kpc--has led to a flurry of theory proposals about their nature and origin. I will discuss one such hypothesis: that ORCs are vortext rings created by the interaction of large scale shocks with fossible radio lobes, and the constraints that can be derived on the cosmic environment they reside in (likely the outskirts of groups and low-mass clusters) and the energetics of the radio galaxies involved in their creation.
9:50 – 10:15
Zooming in on radio relics: How relic morphology probes density fluctuations at the edge of galaxy clusters
Joseph Whittingham | Leibniz Institute for Astrophysics Potsdam (AIP)Abstract ⓘ
TBA
10:15 – 11:10
Coffee Break
11:10 – 11:35
Cluster Merger Shocks in Cosmological and Idealized Box Simulations
Dongsu Ryu | UNIST (Ulsan National Institute of Science and Technology)Abstract ⓘ
TBD
11:35 – 12:00
Turbulence excitation in cosmological simulations of massive galaxy cluster mergers
Lorenzo Maria Perrone | Leibniz-Institute for Astrophysics Potsdam (AIP)Abstract ⓘ
TBA
12:00 – 12:25
Cosmic Ray Transport in Magnetized Turbulence
Philipp Kempski | Instituto Superior Técnico, University of LisbonAbstract ⓘ
TBA
12:25 – 12:40
Poster talks
Exploring a cosmic ray inverse-Compton origin to the SZ-to-X-ray pressure deficit in the cool core cluster ZwCl 3146
Emily Silich | CaltechAbstract ⓘ
TBA
Missing metals in the core of the Centaurus cluster
Tomas Plsek | Masaryk UniversityAbstract ⓘ
TBA
12:40 – 14:00
Lunch
14:00 – 14:25
The topology of the magnetic field in Abell 2255 out its virial radius
Andrea Botteon | INAF-IRAAbstract ⓘ
Magnetic fields in galaxy clusters regulate many aspects of the physics of the intracluster medium (ICM), yet their properties, origin, and evolution remain poorly understood. Evidence for cluster magnetic fields comes from diffuse synchrotron sources (e.g. radio relics and halos), which trace relativistic particles accelerated by shocks and turbulence generated during cluster mergers. In the case of Abell 2255, a plethora of diffuse radio emission is detected, spanning a projected largest linear size of ~5 Mpc and extending out to the cluster virial radius. This emission probes the presence of cosmic rays and magnetic fields on unprecedented spatial scales within the cluster environment.
By leveraging new radio observations performed with LOFAR (more than 300 hours of data, i.e. the deepest observations ever obtained for a galaxy cluster) we have mapped the synchrotron emission from Abell 2255 in unprecedented detail and, by applying the synchrotron intensity gradient technique, we have reconstructed the topology of the underlying magnetic field. In this talk, I will present these results, showing that the magnetic field exhibits preferential orientations in specific regions of the cluster, likely shaped by the dynamics of the thermal gas during the merger process.
By leveraging new radio observations performed with LOFAR (more than 300 hours of data, i.e. the deepest observations ever obtained for a galaxy cluster) we have mapped the synchrotron emission from Abell 2255 in unprecedented detail and, by applying the synchrotron intensity gradient technique, we have reconstructed the topology of the underlying magnetic field. In this talk, I will present these results, showing that the magnetic field exhibits preferential orientations in specific regions of the cluster, likely shaped by the dynamics of the thermal gas during the merger process.
14:25 – 14:50
Synthetic Radio and X-ray Observations of Shocks in Simulated Binary Mergers
Hyesung Kang | Pusan National UniversityAbstract ⓘ
We perform three-dimensional magnetohydrodynamic simulations of idealized binary mergers of galaxy clusters to explore the formation and observable characteristics of radio relics. Cosmic-ray electrons (CRe) are accelerated via diffusive shock acceleration (DSA), while turbulent driving promotes the growth of filamentary magnetic fields through small-scale dynamo processes. Based on the computed electron energy distributions and magnetic field structures, we calculate synchrotron emissivities and construct synthetic radio maps of double-relic configurations. Our results indicate that Fermi-II acceleration with characteristic timescales of ≲1 Gyr substantially extends the postshock cooling time of CRe and enhances radio surface brightness. In contrast, the reacceleration of fossil electron populations primarily elevates the overall emission level without markedly changing the spatial pattern of spectral indices.
We further generate synthetic X-ray and radio images from different viewing angles using the simulation data. We find that Mach numbers inferred from mock X-ray analyses tend to be underestimated because of projection effects, whereas those derived from radio spectral indices at the shock fronts are consistent with the average Mach numbers of relic-forming shocks. Overall, our study underscores the combined roles of merger dynamics, magnetic turbulence, fossil electron content, and projection geometry in determining the morphology and spectral properties of radio relics in cluster outskirts.
We further generate synthetic X-ray and radio images from different viewing angles using the simulation data. We find that Mach numbers inferred from mock X-ray analyses tend to be underestimated because of projection effects, whereas those derived from radio spectral indices at the shock fronts are consistent with the average Mach numbers of relic-forming shocks. Overall, our study underscores the combined roles of merger dynamics, magnetic turbulence, fossil electron content, and projection geometry in determining the morphology and spectral properties of radio relics in cluster outskirts.
14:50 – 15:15
Particle acceleration in intracluster shocks
Damiano Caprioli | University of ChicagoAbstract ⓘ
TBA
15:15 – 16:00
Coffee Break
16:00 – 22:00
Social Program and Dinner
Thursday – 23 July
9:00 – 9:25
Wanted: Simulations of Radio Galaxies and Filaments in the ICM
Lawrence Rudnick | Univ. of MinnesotaAbstract ⓘ
Our current simulations have not kept up with the collosal extent and range of filaments interacting with radio galaxies. Since many filaments are likely illuminated by electrons from the nearby radio galaxies, there is likely a much larger population of currently invisible magnetic threads in the ICM. We need the next generation of radio galaxies, in a variety of magnetized, turbulent environments, both to understand radio galaxy physics, and the hidden structures in the ICM.
9:25 – 9:50
Constraining Models of AGN Feedback with Synthetic X-Ray and SZ Observations
Evan Scannapieco | Arizona State UniversityAbstract ⓘ
AGN feedback plays an essential role in galaxy formation, yet the details of this process remain largely unknown. I will discuss recent work using synthetic observations to test AGN feedback models with current X-ray and Sunyaev-Zel’dovich measurements. While hot-gas observables are sensitive to the properties of the underlying models, the comparisons also uncover important tensions with current simulations and degeneracies between halo properties and observables. I will present a new suite of simulations designed to mitigate these issues by isolating the roles of different feedback and identifying which combinations of X-ray and SZ measurements can place the strongest constraints on AGN feedback.
9:50 – 10:15
Cosmic rays in cosmological simulations - bridging scales
Ludwig Böss | The University of ChicagoAbstract ⓘ
TBA
10:15 – 11:10
Coffee Break
11:10 – 11:35
Mostly thermal and mostly non-thermal ICM
Eugene Churazov | Max Planck Institute for AstrophysicsAbstract ⓘ
TBA
11:35 – 12:00
Particle acceleration in astrophysical shocks: from electrons to cosmic rays
Anatoly Spitkovsky | Princeton UniversityAbstract ⓘ
TBA
12:00 – 12:25
Particle acceleration and transport in galaxy clusters and large scale structures
Gianfranco Brunetti | INAF- Istituto di RadioastronomiaAbstract ⓘ
TBA
12:25 – 12:40
Poster talks
Simulating realistic morphologies of FRI jets with self-regulated AGN feedback
Léna Jlassi | Leibniz Institute for Astrophysics (AIP)Abstract ⓘ
TBA
Role of magnetic Fields in AGN-CGM interactions in massive galaxies at halo masses ∼10^13.5 M⊙
Deovrat Prasad | Cardiff University, UKAbstract ⓘ
The evolution of the most massive halos of the universe like giant elliptical galaxies, galaxy groups or galaxy clusters is fundamentally governed at low redshifts by the complex interplay between radiative cooling of the circumgalactic medium (CGM) and energetic feedback from supermassive black holes. The cooling-heating cycle of the baryons is critically affected by the presence of weak magnetic fields in the CGM. I will present results from my current research on modeling magnetized AGN feedback and multiphase gas dynamics using very high resolution magnetohydrodynamic simulations. My work focuses on understanding how cold gas condenses out of hot halos, how it accretes onto central black holes, and how magnetized jets couple their energy to the surrounding CGM. I will discuss recent results on jet energetics, the stability of feedback cycles, and highlight how these simulations connect with multiwavelength observations.
12:40 – 14:00
Lunch
14:00 – 14:25
The interaction of M86 with the Virgo cluster
Jeremy Sanders | Max Planck Institute for Extraterrestrial Physics (MPE)Abstract ⓘ
We describe the results of an analysis of new Einstein Probe (EP) observations of the M86 subgroup as it plunges towards the Virgo cluster. M86 is one of the closest and clearest examples of the stripping of material during a minor merger. EP is an X-ray observatory designed for transient science. However, using its FXT telescopes, similar to those on eROSITA, we can make wide field X-ray images of the intracluster medium. The data we present come from a performance verification of EP. Using these data we map out the stripped material around M86 and make thermodynamic maps of the interaction with the main cluster. We also examine the stripped material as it interacts with the cluster in terms of its metallicity. In addition, we compare our data with the tails of gas seen in other wavelengths.
14:25 – 14:50
Transport in the intracluster medium
Prakriti Palchoudhury | University of OxfordAbstract ⓘ
TBA
14:50 – 15:15
The PICO-Cluster Project: cluster sample, magnetic field growth, and weakly collisional effects
Christoph Pfrommer | Leibniz Institute for Astrophysik PotsdamAbstract ⓘ
Galaxy clusters constitute a microcosm of the Universe and offer a unique laboratory for studying plasma astrophysics, encompassing processes such as cosmic-ray acceleration and non-thermal radio emission, turbulence, weakly collisional plasma physics, and transformative mechanisms in galaxy evolution. To investigate these phenomena, I will present the PICO-Cluster Project, studying "Plasmas In COsmological Clusters" using a suite of high-resolution cosmological zoom-in simulations of massive galaxy clusters with masses >1e15 M_o that were selected from a parent simulation box with a comoving side length of 1 Gpc/h. In this talk I will discuss our cluster sample, present first results on magnetic field growth and Faraday rotation measures and discuss the importance of weakly collisional effects such as heating by Braginskii viscosity.
15:15 – 16:00
Coffee Break
16:00 – 16:25
Ram pressure stripped tails in galaxy clusters
Ming Sun | University of Alabama in HuntsvilleAbstract ⓘ
TBA
16:25 – 16:50
Cool cores and multi-phase gas in TNG-Cluster
Dylan Nelson | Heidelberg UniversityAbstract ⓘ
TBA
16:50 – 17:15
Lower Decks: Galaxy Cluster Physics in the Local Universe
Klaus Dolag | USM/LMUAbstract ⓘ
TBD
17:15 – 18:00
Discussion
Friday – 24 July
9:00 – 9:25
Bound or blown: the fate of hot gas in galaxy groups
Dominique Eckert | University of GenevaAbstract ⓘ
Because of their shallow gravitational potential compared to more massive galaxy clusters, galaxy groups are highly sensitive to feedback from supermassive black holes (SMBH). Energy injection by SMBH causes the gaseous atmospheres of galaxy groups to expand beyond the virial radius of these systems, which leads to a depletion of baryons and elevated entropies in the inner regions. In this talk, I will present the XMM Group AGN Project (X-GAP), a large program on XMM targeting a carefully selected sample of 49 local galaxy groups. Following a careful assessment of the selection function of the sample, I will describe how the data constrain AGN feedback models through a like-for-like comparison of simulated halos from the FLAMINGO hydrodynamical suite with X-GAP data. I will also present entropy and pressure profiles of galaxy groups in the mass range 1e13-1e14 Msun and an assessment of the integrated non-thermal energy of group-scale halos, which allows us to estimate the conversion efficiency of SMBH energy into heat. I will conclude by discussing the impact of feedback on the mass distribution on Mpc scales, which represents a major source of systematic uncertainty for leading cosmology experiments like Euclid and Rubin.
9:25 – 9:50
Old AGN plasma in galaxy groups
Marisa Brienza | IRA-INAFAbstract ⓘ
TBA
9:50 – 10:15
Scale dependent dynamics in multiphase and magnetized turbulence
Philipp Grete | University of HamburgAbstract ⓘ
TBA
10:15 – 11:10
Coffee Break
11:10 – 11:35
Turbulence in the ICM: Enhanced Collisionality, Magneto-immutability, and the Extended Cascade
Matthew Kunz | Princeton UniversityAbstract ⓘ
TBA
11:35 – 12:00
Cosmic-ray transport and energisation in intermittent ICM environments
Robert Ewart | Princeton UniversityAbstract ⓘ
TBA
12:00 – 12:25
A multi-phase paradigm for turbulent heating and CR transport: CGL simulations and next steps
Stephen Majeski | JILA, University of Colorado and NISTAbstract ⓘ
TBA
12:25 – 13:45
Lunch
13:45 – 14:10
Probing intracluster medium turbulence from deep imaging of Sunyaev-Zel'dovich fluctuations
Rémi Adam | Laboratoire Lagrange (OCA)Abstract ⓘ
TBA
14:10 – 14:35
A XRISM view of chemical enrichment in galaxy clusters
Francois Mernier | IRAPAbstract ⓘ
An essential component of the cosmic cycle of metals is found in the hot, X-ray emitting gas pervading clusters (and groups) of galaxies and the cosmic web. On paper, the collisional ionisation equilibrium of the intracluster medium (ICM) allows extraordinarily accurate measurements of its abundances. In turn, these measurements offer the potential of a thorough understanding of the chemical history and dynamics of our Universe, as well as of the mechanisms of metal production through stellar nucleosynthesis and supernova explosions. In practice, however, the moderate spectral resolution of the latest generation of X-ray missions has limited the ICM abundance accuracy.
In this talk, we demonstrate how the high-resolution spectroscopy offered by XRISM Resolve is changing this paradigm and transforms our understanding of chemical enrichment in the ICM. The talk will focus essentially on the chemical composition (and its spatial distribution) of the Centaurus and the Perseus cluster cores, both observed very deeply (379 ks and 287 ks, respectively) during the XRISM Performance Verification phase. We will also discuss the potential (and current challenges) of XMM-Newton RGS to complement Resolve in ICM abundance studies.
In this talk, we demonstrate how the high-resolution spectroscopy offered by XRISM Resolve is changing this paradigm and transforms our understanding of chemical enrichment in the ICM. The talk will focus essentially on the chemical composition (and its spatial distribution) of the Centaurus and the Perseus cluster cores, both observed very deeply (379 ks and 287 ks, respectively) during the XRISM Performance Verification phase. We will also discuss the potential (and current challenges) of XMM-Newton RGS to complement Resolve in ICM abundance studies.
14:35 – 15:00
Studying the Hot Universe at Masaryk University
Norbert Werner | Masaryk UniversityAbstract ⓘ
TBA
15:00 – 15:45
Discussion
15:45 – 16:30
Coffee Break
16:30
Conference end
Posters
Validating the ICL+BCG Fraction in Projection as a Dynamical Age Tracer of Galaxy Clusters Using the Lowerdecks Zoom-in Simulations
Shubhan Bhatia | LMU/USMAbstract ⓘ
Upcoming wide-field surveys like Euclid and LSST will open a new window into the low-surface-brightness universe, making it possible to map the diffuse stellar light in galaxy clusters. Recent work by Kimmig et al. (2025) established a clear correlation between cluster formation redshift (z_form) and the true 3D fraction of the combined Brightest Cluster Galaxy and Intracluster light (ICL+BCG). However, observational studies are fundamentally limited to 2D projections. The primary goal of this work is to determine whether observationally derived 2D ICL+BCG fractions can serve as equally reliable tracers of z_form. To test this, we generate mock observations in the Euclid I_E optical band using the Lowerdecks suite, a set of high-resolution hydrodynamic zoom-in simulations of individual clusters from the SLOW constrained Local Universe 500 Mpc/h box. To rigorously quantify the statistical scatter introduced by line-of-sight variations, our pipeline creates 2D surface brightness maps using a smoothed particle hydrodynamics (SPH) projection method across an ensemble of 100 random orientations per cluster. We systematically isolate the ICL+BCG component using a variety of fixed and dynamic satellite-masking apertures alongside an isophotal surface brightness threshold of 30 mag/arcsec^2. By directly comparing these mock 2D fractions to their 3D counterparts within the same simulated clusters, we evaluate how projection effects, mask choices, and surface brightness limits impact the observed scatter. This framework provides a direct calibration between upcoming Euclid observables and the underlying assembly histories of massive clusters.
SBI inference of ICM thermodynamics
Joey Braspenning | Max Planck Institute for AstronomyAbstract ⓘ
Understanding the thermodynamic state of galaxy clusters is of paramount importance to understanding their evolution and constraining baryonic physics. Traditional methods of inferring temperature and metallicity typically extract a single value, which, it has recently been shown, can be significantly biased. We completely circumvent this problem, by applying simulation-based-inference (SBI) to spectra of individual lines-of-sight (LOS) of galaxy groups and clusters, extracting the full temperature and metallicity distribution over 3 orders of magnitude. Our SBI uses a convolutional neural network trained on output from the TNG-Cluster simulations. We generate both XRISM- and CHANDRA-like spectra for each gas cell in the simulation and use LOS projected spectra to train simultaneously on low- and high-resolution spectra. The result is a tool that can take an X-ray spectrum coming from either an CCD or microcalorimeter and reproduce the line-of-sight temperature and metallicity distribution. We provide error bars on the measurements and have feature-importance test with SHAP which tell us which part of the spectra are used to predict the thermodynamic distribution. We verify the working of our method on the FLAMINGO simulations. This tool is a step in the direction of extracting a large additional amount of information from X-ray observations, and unlocking our knowledge of their internal workings.
Turbulence in the ICM: what is XRISM really measuring?
Dimitris Chatzigiannakis | MPIAAbstract ⓘ
XRISM, with its high spectral resolution, is providing us with robust measurements of the turbulent motion of the ICM. These values seem to be on the low end of the values predicted by current cosmological models, hinting at a possible tension. However, these comparisons tend to be heterogeneous or rely on low statistics. In this work, we analyse the turbulence in the ICM of galaxy clusters from the IllustrisTNG suite of cosmological magnetohydrodynamical simulations of galaxies in an observer-like manner, in order to understand the properties of the gas XRISM is sensitive to. We also highlight how those measurements compare to the intrinsic velocity structure of the ICM, as predicted by the IllustrisTNG model, focusing on the impact observational realism and cluster selection have on the implications.
Radio emission in MACSJ0018
Paola Dominguez Fernandez | Harvard UniversityAbstract ⓘ
We present the first detailed numerical modeling of the radio emission from MACS J0018.5+1626 as part of the Improved Constraints on Mergers with SZ, Hydrodynamical simulations, Optical, and X-ray (ICM-SHOX) project. By matching X-ray, thermal and kinetic Sunyaev-Zel'dovich, optical and lensing observables to simulations, the ICM-SHOX pipeline indicates that MACS J0018.5+1626 is undergoing a binary merger close to pericenter passage and is observed along a line of sight nearly aligned with the merger axis. We perform three-dimensional magnetohydrodynamic simulations of binary cluster mergers coupled to tracer particles and a Fokker-Planck solver to model the radio emission. Exploring variations in the most likely initial conditions within the ICM-SHOX parameter space, such as the relative cluster velocity and impact parameter, we find that the resulting merger configuration consistently produces two merger-driven shocks with typical average Mach numbers 2-3 with corresponding standard deviations of 0.5-1.5. Within this framework, we examine the cluster conditions under which standard diffusive shock acceleration can reproduce LOFAR observations. In particular, we discuss the possibility that the apparent radio halo seen by LOFAR arises from the superposition of two radio relics viewed nearly face-on.
Probing ICM turbulence with MHD exascale simulations
Martin Fournier | Hamburg UniversitatAbstract ⓘ
TBA
The evolving ICM: XRISM insights into kinematic and non-equilibrium physics in merging clusters
Annie Heinrich | University of ChicagoAbstract ⓘ
TBA
Beyond the Spherical Cow: Multiphase Gas Survival in Realistic Cluster Environments
Fernando Hidalgo Pineda | Max Planck Institute for AstrophysicsAbstract ⓘ
The intracluster medium (ICM) is now known to host a rich multiphase structure, including dusty, molecular, and cold atomic gas. Such material must be transported through a hot, volume-filling plasma, either via large-scale outflows from cluster cores or through ram-pressure stripping and infall of galaxies. In both cases, the survival and acceleration of cold gas present a long-standing challenge: cold clumps are expected to be rapidly shredded by hydrodynamic instabilities and mixing. While it is well established that radiative cooling can offset this destruction, most existing “cloud-crushing” studies rely on highly idealized, spherical cloud geometries, leaving open how these conclusions generalize to realistic interstellar media. In this talk, I present new theoretical and numerical results that address this problem across the full lifecycle of multiphase gas in the ICM. On the outflow and stripping side, I develop a framework that replaces isolated spherical clouds with a fractal, multiphase ISM subject to ram pressure. I show that when the hot phase acts on a sufficiently large effective ISM depth, cooling dominates over destructive mixing. This leads to a generalized survival criterion expressed in terms of the effective depth of the cold phase and naturally resolves the apparent tension between efficient acceleration and long cloud lifetimes. Cold gas then assembles into plumes or confined shells of characteristic size ∼χ r_cl,min, growing as mass is accreted from the hot phase and thereby determining whether coherent tails form. I then discuss the subsequent evolution of this cold gas as it infalls through a stratified, turbulent ICM, demonstrating that the coupled effects of turbulence, cooling, and gravity fundamentally alter the morphology, kinematics, and mass distribution of the multiphase medium, with direct implications for cold-gas budgets in cluster cores and the fueling of galaxies.
Exploring the physics of the intracluster medium with jellyfish galaxies
Alessandro Ignesti | Astronomical Institute of the Czech Academy of SciencesAbstract ⓘ
Jellyfish galaxies are the most extreme outcomes of ram pressure stripping in galaxy clusters, and their multiphase tails offer a unique laboratory for probing the microphysics of the intracluster medium (ICM). Recent works have demonstrated how the interaction between stripped interstellar medium and the surrounding IMC constrains fundamental ICM properties, such as magnetic fields and viscosity. Based on the recent results from the GASP survey (Ignesti et al. 2024, 2026), I will first show how the survival of cold gas in these tails can be regulated by the galaxy’s orbital dynamics. We find that supersonic motion through the ICM can trigger shock compression and magnetic draping, which protect the stripped gas from evaporation and enable extraplanar star formation. Secondly, I will present a systematic analysis of the Velocity Structure Function (VSF) of ionized gas within these tails. By tracing the warm plasma small-scale motions down to kiloparsec scales, we find that the stripped ISM VSF can infer the underlying ICM turbulent motions. Moreover, the resulting turbulence spectra suggest that the ICM viscosity is suppressed by orders of magnitude (0.3%–25%) relative to the Spitzer value. These findings suggest that the ICM behaves as a weakly collisional plasma, where small-scale magnetic field fluctuations can significantly reduce the effective mean free path.
Constraining the viscosity of ICM with baryon-dominated dwarf galaxies
Anna Ivleva | University Observatory MunichAbstract ⓘ
Evaluating the effective viscosity in the ICM remains a challenging task, as the systematic uncertainties associated to Reynolds number measurements are difficult to control. Such evaluations are typically based on the properties of AGN outflows visible in X-ray. Meanwhile, the recent advent of low-surface brightness astronomy has revealed the presence of baryon-dominated dwarfs inside galaxy clusters. Due to their relatively massive gas component, the evolution and dynamical behavior of these objects is expected to depend on the state of the surrounding ICM. The viscosity of the ICM will be naturally reflected in the properties of such galaxies, as it determines the mixing ability of the multiphase gas at the dwarf’s interface, which in turn will impact the star formation behavior.
By utilizing high-resolution hydrodynamic simulations of baryon-dominated dwarfs inside galaxy clusters, I investigate what directly observable properties can be used as tracers for a viscous ICM. A plausible setup is ensured by fully resolving a merger event in the outskirts of a cluster, which yields realistic seed populations of dwarf galaxies that are inherently gas-dominated due to their tidal origin. Varying viscosity from minimum (numerically limited) to full Spitzer value reveals a trend of enhanced star-forming main sequences in an inviscid ICM. Additionally, I show that these galaxies remain very diffuse due to efficient mixing at their boundary with the ICM, while viscous realizations of the same setup can yield compact ellipticals. Finally, I review the viscosity-driven impact on the orbit of dwarfs and discuss the resemblance of these simulated objects to peculiar dwarf galaxies already observed inside galaxy clusters.
By utilizing high-resolution hydrodynamic simulations of baryon-dominated dwarfs inside galaxy clusters, I investigate what directly observable properties can be used as tracers for a viscous ICM. A plausible setup is ensured by fully resolving a merger event in the outskirts of a cluster, which yields realistic seed populations of dwarf galaxies that are inherently gas-dominated due to their tidal origin. Varying viscosity from minimum (numerically limited) to full Spitzer value reveals a trend of enhanced star-forming main sequences in an inviscid ICM. Additionally, I show that these galaxies remain very diffuse due to efficient mixing at their boundary with the ICM, while viscous realizations of the same setup can yield compact ellipticals. Finally, I review the viscosity-driven impact on the orbit of dwarfs and discuss the resemblance of these simulated objects to peculiar dwarf galaxies already observed inside galaxy clusters.
The Impact of ICM Ram Pressure on the Molecular Component of Cluster Galaxies
Pavel Jachym | Astronomical Institute, Czech Academy of SciencesAbstract ⓘ
The ALMA JELLY project targets 28 jellyfish galaxies in the nearby clusters Coma, Leo and Norma, providing a unique laboratory for studying how the intracluster medium governs the evolution of the molecular gas component in galaxies undergoing ram pressure stripping. The sample spans a wide range of ICM conditions and stripping stages, enabling us to trace how molecular gas is displaced, compressed, transformed, or destroyed as galaxies interact with the surrounding medium. We present the survey’s first results, focusing on the incidence, distribution, and physical state of molecular gas in both galaxy disks and stripped tails, and on how these properties correlate with local ICM pressure and interaction conditions.
Simulating realistic morphologies of FRI jets with self-regulated AGN feedback
Léna Jlassi | Leibniz Institute for Astrophysics (AIP)Abstract ⓘ
TBA
Simulating cosmic rays and their non-thermal emission in the ICM
Daniel Karner | LMU MunichAbstract ⓘ
Observations of radio halos and giant relics have firmly established that the ICM of many galaxy clusters contains a population of relativistic, synchrotron-emitting electrons. They are (re)accelerated both on large scales via MHD turbulence in the ICM and merger/accretion shocks and on smaller scales via supernova and AGN feedback in individual galaxies. Most of these processes should also accelerate cosmic-ray (CR) protons, which then accumulate in the ICM due to their long cooling timescale. Furthermore, inelastic collisions with thermal protons in the ICM produce neutral pions, which then decay into gamma-rays. However, for most galaxy clusters only upper limits of this hadronic gamma-ray emission have been measured, which poses a strong constraint on modelling the injection and transport of CR protons in the ICM. A solution that has emerged over previous years is that the acceleration efficiency of weak high-beta shocks was severely overestimated in the past compared to most recent particle-in-cell simulations, which also show that the geometry of ICM shocks preferably accelerates CR electrons.
We revisit this problem by including additional sources of cosmic-rays and the most important energy loss processes in the cosmological TreePM-SPH code OpenGadget3. We then perform cosmological radiative MHD simulations of galaxy clusters, where the spectrally resolved CR protons and electrons are evolved on the fly, and compare the resulting non-thermal synchrotron and gamma radiation with observations.
We revisit this problem by including additional sources of cosmic-rays and the most important energy loss processes in the cosmological TreePM-SPH code OpenGadget3. We then perform cosmological radiative MHD simulations of galaxy clusters, where the spectrally resolved CR protons and electrons are evolved on the fly, and compare the resulting non-thermal synchrotron and gamma radiation with observations.
ORCs of groups, groups of ORCs: emerging picture from X-ray observations and cosmological simulations
Ildar Khabibullin | Oxford UniversityAbstract ⓘ
Odd Radio Circles (ORCs) are a newly discovered class of radio sources showing large-scale, ring-like diffuse radio emission with a diameter of hundreds of kpc, around central, elliptical galaxies, previously without any detected counterparts at other wavelengths. The extent, as well as the complex morphology of the different detected ORCs, have led to numerous speculations on their origin and formation: a relic lobe of a giant radio galaxy seen edge-on; a giant blast wave, possibly from a binary supermassive black hole merger; interactions between a tailed radio galaxy and its environment including neighboring galaxies; an expanding synchrotron shell from a starburst termination shock in the host galaxy. Another, far-reaching possibility, hinted by zoom-in cosmological simulations, is that these are merger-driven shocks, similar to what is observed as radio relics in galaxy clusters, propagating into the outer circum-galactic and intragroup media. Almost all of the known ORCs are centered on galaxies at redshifts of 0.25-0.6, precluding reliable detection of the predicted faint diffuse X-ray emission with the currently operating X-ray facilities. However, the ongoing EMU survey with the Australian SKA Pathfinder has revealed several such sources with complex radio shells at much lower redshifts: Physalis (z=0.017), Cloverleaf (z=0.05), and the double-ring ORC J1841-6547 (z~0.18). I’ll describe what we currently know about their X-ray emission, how this compares with predictions from cosmological zoom-in simulations, and what are the prospects for the nearest and more distant future.
Automated Search for X-ray Cavities using Deep Learning
Martin Kolář | Masaryk UniversityAbstract ⓘ
TBA
“Brick” or “Mist”? Investigating Multiphase Gas Dynamics in Cool-core Galaxy Clusters
Yi-Yang Li | National Tsing Hua UniversityAbstract ⓘ
Cold gas with T~1e4 K is often observed in cool-core clusters, but their nature remains elusive. Theoretical models of thermal instabilities predict that they should fragment to sizes on the ~10 pc scales, unresolvable by typical resolution of observations as well as numerical simulations. Therefore, it is an open question whether the cold gas should behave as “mist”, which passively follows evolution of the hot gas, or as “brick”, which still has non-negligible dynamical influence on the hot gas. In this study, we analyze kinematics of cold gas from two sets of simulations (the “Mist” and “Brick” models, respectively) and compare the predicted line-of-sight velocity dispersions with recent observations. We find that the hot gas is less disturbed in the Mist scenario compared to the Brick model. Recent studies showed that the hot gas velocity dispersion observed by XRISM is lower by a factor of 1.5 - 1.7 compared with values predicted by cosmological simulations. Our results suggest that considering the fragmentation of cold gas in the Mist scenario could help to alleviate the discrepancy.
Viscous or Turbulent? The XRISM Puzzle of Coma
Tirso Marin-Gilabert | Center for Astrophysics | Harvard & SmithsonianAbstract ⓘ
TBA
Resolving AGN Feedback in Cluster Cores with XRISM and Chandra
Hannah McCall | University of ChicagoAbstract ⓘ
TBA
Exploring shock structures in Cosmic Web
Barbora Miklošová | Masaryk UniversityAbstract ⓘ
TBA
Turbulent cosmic-ray reacceleration in radio bridges
Kosuke Nishiwaki | INAF IRAAbstract ⓘ
Observations of diffuse radio emission provide crucial clues to one of the long-standing problems in cluster astrophysics: how magnetic fields and relativistic particles are energized in the cluster environment. In this work, we focus on radio bridges observed in the inter-cluster region between two merging clusters, such as Abell 399–Abell 401, and investigate non-thermal phenomena in cluster outskirts and cosmic filaments using state-of-the-art numerical simulations.
We simulate the evolution of a merging cluster system with the cosmological MHD code Enzo. We implement a runtime Lagrangian tracer-particle method in Enzo and use it to follow the trajectories of baryonic matter. In post-processing, we solve the Fokker–Planck equation for all (approx. 10 million) tracer particles, evaluating cooling and reacceleration efficiencies from the local MHD quantities recorded along each tracer trajectory.
Our simulation suggests that the bridge region is filled with turbulence generated by mergers of small clumps and by gas compression as the two clusters approach each other. The simulated bridge successfully reproduces several observed properties of the radio bridge in A399–401, including its spectral shape, intensity profile, and pixel-by-pixel correlation between radio and X-ray intensities.
Finally, we present our newly developed GPU-accelerated Fokker–Planck solver, which achieves a throughput nearly 100 times higher than that of the MPI-based solver used in our previous work.
We simulate the evolution of a merging cluster system with the cosmological MHD code Enzo. We implement a runtime Lagrangian tracer-particle method in Enzo and use it to follow the trajectories of baryonic matter. In post-processing, we solve the Fokker–Planck equation for all (approx. 10 million) tracer particles, evaluating cooling and reacceleration efficiencies from the local MHD quantities recorded along each tracer trajectory.
Our simulation suggests that the bridge region is filled with turbulence generated by mergers of small clumps and by gas compression as the two clusters approach each other. The simulated bridge successfully reproduces several observed properties of the radio bridge in A399–401, including its spectral shape, intensity profile, and pixel-by-pixel correlation between radio and X-ray intensities.
Finally, we present our newly developed GPU-accelerated Fokker–Planck solver, which achieves a throughput nearly 100 times higher than that of the MPI-based solver used in our previous work.
Missing metals in the core of the Centaurus cluster
Tomas Plsek | Masaryk UniversityAbstract ⓘ
TBA
Role of magnetic Fields in AGN-CGM interactions in massive galaxies at halo masses ∼10^13.5 M⊙
Deovrat Prasad | Cardiff University, UKAbstract ⓘ
The evolution of the most massive halos of the universe like giant elliptical galaxies, galaxy groups or galaxy clusters is fundamentally governed at low redshifts by the complex interplay between radiative cooling of the circumgalactic medium (CGM) and energetic feedback from supermassive black holes. The cooling-heating cycle of the baryons is critically affected by the presence of weak magnetic fields in the CGM. I will present results from my current research on modeling magnetized AGN feedback and multiphase gas dynamics using very high resolution magnetohydrodynamic simulations. My work focuses on understanding how cold gas condenses out of hot halos, how it accretes onto central black holes, and how magnetized jets couple their energy to the surrounding CGM. I will discuss recent results on jet energetics, the stability of feedback cycles, and highlight how these simulations connect with multiwavelength observations.
AGN feedback as a driver of spiral-like gas structures and cold fronts in cool-core clusters
Majidul Rahaman | National Tsing Hua University, TaiwanAbstract ⓘ
Spiral features and cold fronts in cool-core (CC) galaxy clusters are among the most striking signatures of intracluster medium (ICM) dynamics, and are almost always interpreted as the result of minor merger-induced gas sloshing. Here, we show that AGN feedback alone can produce the same structures, without any external perturbation. Using three-dimensional cosmic-ray magnetohydrodynamic (CR-MHD) simulations of a Perseus-like cluster, we find that precessing, CR-dominated jets naturally drive spiral-like structures extending to ~150 kpc and accompanying cold fronts, through the coherent fallback of jet-uplifted gas during AGN quiescent phases. Comparing against XRISM/Resolve observations of Perseus, we find that while an off-axis merger broadly reproduces the large-scale velocity gradients, it falls short in the central ~30 kpc, a region where AGN-driven motions appear to dominate. We further show that during quiescent phases, both the velocity and magnetic fields develop an episodic, centrally confined tangential bias that stabilises cold fronts against Kelvin–Helmholtz instabilities. This behaviour is physically distinct from the more persistent, spatially extended tangential bias seen in merger simulations, and points to AGN feedback as the dominant driver of ICM structure in the innermost cluster core.
Turbulent Drivers of Multiphase Structure in the ICM: Insights from TNG Cluster simulations
Bipradeep Saha | Max Planck Institute for AstronomyAbstract ⓘ
Multiphase gas is a defining feature of the intracluster medium (ICM), particularly in systems shaped by active galactic nucleus (AGN) feedback and large-scale dynamical processes. Yet, the origin, evolution, and kinematic properties of these phases remain poorly constrained. Using the TNG-Cluster suite of high-resolution cosmological MHD simulations, we investigate the formation and dynamics of multiphase gas in galaxy clusters, focusing on the turbulent and bulk motion signatures imprinted by AGN activity and mergers.
Through a kinematic decomposition of the ICM velocity field, we isolate turbulent motions and study their role in driving phase transitions, mixing, and thermal instabilities. We find that turbulence accounts for only 30–50% of the total velocity dispersion across a wide diversity of simulated clusters at redshift zero, but can increase by ~15% in systems with active feedback, cool-core sloshing, or prominent X-ray cavities—conditions often associated with the emergence of cooler gas phases. We also show that AGN feedback drives short lived, high velocity outflows which enhances turbulence in core of galaxy clusters.
We further explore how different temperature phases co-evolve, interact, and respond to AGN-driven outflows. This provides theoretical constraints on the morphology and kinematics of multiphase ICM and highlights the challenges of modeling such systems across orders of magnitude in scale and temperature. Our results offer a bridge between simulations and upcoming high-resolution X-ray observations, and contribute to the broader understanding of multiphase structure formation in astrophysical plasmas.
Through a kinematic decomposition of the ICM velocity field, we isolate turbulent motions and study their role in driving phase transitions, mixing, and thermal instabilities. We find that turbulence accounts for only 30–50% of the total velocity dispersion across a wide diversity of simulated clusters at redshift zero, but can increase by ~15% in systems with active feedback, cool-core sloshing, or prominent X-ray cavities—conditions often associated with the emergence of cooler gas phases. We also show that AGN feedback drives short lived, high velocity outflows which enhances turbulence in core of galaxy clusters.
We further explore how different temperature phases co-evolve, interact, and respond to AGN-driven outflows. This provides theoretical constraints on the morphology and kinematics of multiphase ICM and highlights the challenges of modeling such systems across orders of magnitude in scale and temperature. Our results offer a bridge between simulations and upcoming high-resolution X-ray observations, and contribute to the broader understanding of multiphase structure formation in astrophysical plasmas.
Physical Conditions of the Multi-phase ISM in the Ram-Pressure-Stripped Tail of ESO 137-001
Aashiya Anitha Shaji | Astronomical Institute of Czech Academy of SciencesAbstract ⓘ
Ram-pressure stripping dramatically reshapes the evolution, and therefore the ecosystem, of cluster galaxies by removing their interstellar gas. This process produces extended multi-phase gas tails where cooling, turbulence, and star formation continue even outside galactic disks. Although extra-planar star formation has been observed in several stripped systems, it remains unclear how gas can cool and form stars within the hot intracluster medium instead of rapidly evaporating. We present a multi-wavelength study of the stripped tail of ESO 137-001, the nearest known jellyfish galaxy. This galaxy is part of the ALMA-JELLY large program, a sample of 29 galaxies aimed at understanding how cold molecular gas survives, evolves, and forms stars in extreme environments. Combinining ALMA CO observations of molecular gas with MUSE Hα observations of ionized gas, MeerKAT HI and APEX [CI] observations tracing atomic gas, we investigate the physical properties of the stripped interstellar medium across different regions of the tail. We also explore the relationship between gas content, star formation activity, and local dynamical conditions to examine how gas excitation and phase balance vary from the stellar disk into the stripped tail. Together, these measurements provide insight into the processes that regulate the evolution of multi-phase gas and the persistence of star formation outside galactic disks.
Exploring a cosmic ray inverse-Compton origin to the SZ-to-X-ray pressure deficit in the cool core cluster ZwCl 3146
Emily Silich | CaltechAbstract ⓘ
TBA
Quantifying Gas Fallback in Ram Pressure Stripping Events with Hydrodynamical Simulations
Harrison Souchereau | Yale UniversityAbstract ⓘ
TBA
Magnetization of Galaxy Protoclusters at High Redshift
Larissa Tevlin | Leibniz Institute for Astrophysics PotsdamAbstract ⓘ
TBA
Two-Phase Structure of Synchrotron-Cooling-Unstable Relativistic Plasma
Agnieszka Wierzchucka | University of OxfordAbstract ⓘ
Relativistic, synchrotron-cooling, high-beta plasmas are susceptible to the synchrotron cooling instability (SCI). The SCI is triggered when a local enhancement of the magnetic field creates a region that cools faster than its surroundings. The resulting drop in thermal pressure causes plasma compression to maintain pressure balance, which further increases the magnetic field, creating a positive feedback loop. The SCI has only been studied within a one-dimensional MHD framework. However, since synchrotron emission is anisotropic, particles with large pitch angles are cooled preferentially, leading to a negative pressure anisotropy and subsequent excitation of the firehose instability. We present a physical picture of the nonlinear multi-scale evolution of the SCI in radiative, magnetized, collisionless relativistic plasma, using 2D PIC simulations. We find that the SCI causes the plasma to split into two phases. One phase has a high beta and is infested with firehose fluctuations, which provide an isotropising effect. The second phase has low beta, so firehose modes are suppressed, allowing large pressure anisotropies to grow. We propose a fluid model for collisionless, radiating plasmas and compare it with PIC simulations to quantify the effect of the firehose instability on the SCI. Our study provides a comprehensive description of radiative magnetised plasmas and offers an attractive explanation of the enigmatic filamentary structures observed in galactic centres.
Simulating jets in a turbulent ICM: toward reproducing synchrotron-emitting filaments
Francesca Zanetti | INAF-IRA and University of BolognaAbstract ⓘ
Radio galaxies in galaxy clusters display remarkably complex and disturbed morphologies. These are most likely a result of interactions between the jets of the radio galaxy and the Intra-Cluster Medium that surrounds them.
High-resolution and deep radio observations of radio galaxies in galaxy clusters have also shown the presence of filamentary synchrotron emission probably linked to the jets of the radio galaxy (Rudnick et al. 2022, Brienza et al. 2025, de Rubeis et al. 2025, Ramatsoku et al. 2020). Such filaments typically have widths of a few kiloparsecs and lengths of tens to hundreds of kpc (Rudnick et al. 2022, Brienza et al. 2025, de Rubeis et al. 2025, Ramatsoku et al. 2020). Polarization studies on some of these structures suggest the presence of a magnetic field directed along the filament (Rudnick et al. 2022).
The origin of synchrotron-emitting filaments is still unknown; however, the most favored scenario involves the interaction of a magnetized ICM clump with the jet of a radio galaxy (Rudnick et al. 2022). The fact that these filaments emit synchrotron radiation suggests the presence of high-energy electrons and locally aligned and enhanced magnetic fields. Proposed mechanisms include betatron re-acceleration of electrons driven by turbulent ICM eddies stretching and bending local magnetic field lines, and magnetic reconnection between ICM and jet field lines releasing energy that accelerates electrons (Rudnick et al. 2022).
Traditional simulations of jets in galaxy clusters can reproduce the complex morphologies of radiogalaxies but so far have failed in reproducing the synchrotron-emitting filaments. The reason for this is that key physical processes, such as a turbulent external medium, are missing in the simulations.
To overcome this gap, we have developed a gPLUTO (Mignone+07) simulation setup of a jet propagating in a turbulent external medium. The setup generates a turbulent ambient medium into which a bi-polar jet is then injected.
We tested the setup by creating a set of runs with different jet powers, jet magnetization parameters and average speed of the ambient medium. Each run has a box size of about 350 kpc per side and a resolution of 1 kpc. We calculated the synchrotron emission in post-processing by assuming a power-law energy spectrum for electrons. We can recover disturbed morphologies for the jets and some structures that appear to be filamentary. This is an improvement with respect to previous simulations, however, at this stage we are not sure that the structures we recover are the ones observed by radio-telescopes. This is partly because the spectrum we have been assuming so far for the electrons does not consider their aging and partly because we still lack reliable statistics from observations.
While a direct morphological comparison with observed filaments requires further development (including electron aging in the spectral modeling and higher-resolution runs) these simulations represent a meaningful step toward understanding how jet-ICM interactions give rise to coherent filamentary structures, with implications for particle acceleration and magnetic field amplification in the ICM.
High-resolution and deep radio observations of radio galaxies in galaxy clusters have also shown the presence of filamentary synchrotron emission probably linked to the jets of the radio galaxy (Rudnick et al. 2022, Brienza et al. 2025, de Rubeis et al. 2025, Ramatsoku et al. 2020). Such filaments typically have widths of a few kiloparsecs and lengths of tens to hundreds of kpc (Rudnick et al. 2022, Brienza et al. 2025, de Rubeis et al. 2025, Ramatsoku et al. 2020). Polarization studies on some of these structures suggest the presence of a magnetic field directed along the filament (Rudnick et al. 2022).
The origin of synchrotron-emitting filaments is still unknown; however, the most favored scenario involves the interaction of a magnetized ICM clump with the jet of a radio galaxy (Rudnick et al. 2022). The fact that these filaments emit synchrotron radiation suggests the presence of high-energy electrons and locally aligned and enhanced magnetic fields. Proposed mechanisms include betatron re-acceleration of electrons driven by turbulent ICM eddies stretching and bending local magnetic field lines, and magnetic reconnection between ICM and jet field lines releasing energy that accelerates electrons (Rudnick et al. 2022).
Traditional simulations of jets in galaxy clusters can reproduce the complex morphologies of radiogalaxies but so far have failed in reproducing the synchrotron-emitting filaments. The reason for this is that key physical processes, such as a turbulent external medium, are missing in the simulations.
To overcome this gap, we have developed a gPLUTO (Mignone+07) simulation setup of a jet propagating in a turbulent external medium. The setup generates a turbulent ambient medium into which a bi-polar jet is then injected.
We tested the setup by creating a set of runs with different jet powers, jet magnetization parameters and average speed of the ambient medium. Each run has a box size of about 350 kpc per side and a resolution of 1 kpc. We calculated the synchrotron emission in post-processing by assuming a power-law energy spectrum for electrons. We can recover disturbed morphologies for the jets and some structures that appear to be filamentary. This is an improvement with respect to previous simulations, however, at this stage we are not sure that the structures we recover are the ones observed by radio-telescopes. This is partly because the spectrum we have been assuming so far for the electrons does not consider their aging and partly because we still lack reliable statistics from observations.
While a direct morphological comparison with observed filaments requires further development (including electron aging in the spectral modeling and higher-resolution runs) these simulations represent a meaningful step toward understanding how jet-ICM interactions give rise to coherent filamentary structures, with implications for particle acceleration and magnetic field amplification in the ICM.