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Mateusz Ruszkowski

Publications and source records attributed to Mateusz Ruszkowski.

At least 19 recordsLinked to original sources

On the generation of astrophysically-relevant intermittent magnetic turbulence in the laboratory

Intermittent magnetic turbulence, namely the presence of non-ordered and clusterized fields, is a ubiquitous phenomenon in space and astrophysical plasmas. It is currently understood that it plays a crucial role in the dynamics of astrophysical systems at all scales, from influencing the evolution of the cosmos as a whole to governing local particle acceleration. While there is direct evidence of turbulence in the solar wind, and despite progress obtained through multi-wavelength observations, most of our knowledge of it outside the solar system derives from indirect evidence, through modeling. Here we show that magnetic turbulence, that quantitatively matches that measured in space, can be reproduced in the laboratory. Starting from a homogeneous magnetized plasma, we randomly perturb it using a speckled laser beam. Using proton radiography, we can follow the development and quantitatively characterize the produced intermittent turbulence from its inception.

physics.plasm-ph

The Self-Limiting Nature of Jet-Modulated Thermal Conduction in Cool Core Clusters

Conduction as a mechanism for explaining the disrupted cooling-flow in galaxy clusters has been mostly discounted, as the process is inefficient at transporting heat all the way from the cluster into the core. However, thermal conduction can be strongly enhanced when materials of significantly different temperature are brought into proximity, and thus into close thermal contact. Jets of active galactic nuclei may act as heat pumps by bringing low-entropy gas from the cluster core into thermal contact with the hot outer atmosphere of the cluster, significantly increasing the feedback efficiency of active galactic nuclei. We test this hypothesis by running a suite of 3D magnetohydrodynamic simulations of active galactic nuclei jets in a Perseus-like cluster, including anisotropic conduction. We find that the heat pump efficiency $\eta$ can reach up to 50\% of the maximum possible efficiency $\eta_{\rm max}$ if conduction operates near the Spitzer-Braginskii limit, while $\eta\approx f_{\rm sp}\eta_{\rm max}$ if conduction along the field lines is substantially suppressed below the Spitzer-Braginskii value by a factor $f_{\rm sp}$ by kinetic effects, as recently suggested. We further find that jet-induced thermal conduction is self-limiting: Magnetic draping during the uplift results in a magnetic field orientation close to perpendicular to the induced temperature gradients, significantly reducing conduction along the ideal conductive pathways. Thus, for conservative assumptions about thermal conduction suppression by $f_{\rm sp} \lesssim 0.1$, the heat pump effect leads to only marginal heat transfer and, correspondingly, to immaterial changes in the overall thermal evolution of cool core clusters beyond the isolated effects of conduction and jet-induced heating alone.

astro-ph.HE

Particle Acceleration in Magnetized Shear-Driven Turbulence

Shear flows, ubiquitous in space and astrophysical plasmas, can accelerate particles through turbulence excited by the Kelvin-Helmholtz instability. We present the first numerical study of particle acceleration in sustained, subsonic, non-relativistic, and magnetized turbulence driven purely by velocity shear, including full particle backreaction. Using two-dimensional MHD-PIC simulations with an initially uniform flow-aligned magnetic field and external stirring force, we demonstrate that, in this subsonic regime, sustained particle acceleration requires continuously driven turbulence, whereas freely decaying turbulence rapidly depletes its energy reservoirs and halts the acceleration. The acceleration mechanism operates through the systematic distortion of gyro-orbits by turbulent electric fields: acceleration phases extend the particle trajectory along the electric force, increasing the energy gain, while deceleration phases shorten the trajectory, reducing the energy loss. This asymmetry produces net energy gain despite stochastic fluctuations, with the mean energy change scaling quadratically with shear velocity, characteristic of second-order Fermi acceleration. Initially monoenergetic particles develop substantial non-thermal tails after the turbulence onset. The energization of particles that repeatedly cross shear layers follows geometric Brownian motion, yielding a log-normal distribution. High-energy particles exhibit pitch-angle anisotropy, becoming preferentially perpendicular to the flow-aligned magnetic field as their gyroradii exceed the turbulent layer width. These results establish shear-driven turbulence as a viable particle acceleration mechanism, providing a general model for particle energization in shear flows.

astro-ph.HE

Disentangling AGN Feedback and Sloshing in the Perseus Cluster with XRISM: Insights from Simulations

High-resolution X-ray spectroscopy with XRISM has revealed complex, non-monotonic velocity dispersion profiles in the Perseus cluster, pointing to a complex interplay between at least two physical drivers of motions caused by dynamical processes within the intracluster medium (ICM). To further explore this conclusion, we perform a suite of idealized, controlled simulations targeting the relative roles of merger-induced sloshing and active galactic nucleus (AGN) feedback. Our models systematically isolate and combine these mechanisms to predict observable velocity profiles and X-ray line shapes, providing direct comparison to XRISM and Hitomi data. We find that neither sloshing nor AGN activity alone can reproduce the observed velocity dispersion profile; only their combined action matches the elevated dispersions both at the cluster core and outskirts. Power-spectrum analysis reveals distinct spatial signatures: sloshing generates large-scale coherent motions, while AGN feedback injects turbulence and broadens the velocity spectrum at small scales, especially in the core. By forward-modeling spectral line profiles, we show how these dynamics imprint unique observational signatures on X-ray emission. Our results underscore the necessity of accounting for both large-scale and small-scale drivers of gas motions in the ICM when interpreting high-resolution spectroscopic data, and provide guidance for the analysis of forthcoming XRISM observations.

astro-ph.HE

The Impact of Cosmic Ray Transport on the $\gamma$-Ray Luminosity of Diffuse Gas

Observations of $\gamma$-rays from diffuse gas provide the opportunity to study the distribution of high energy particles in different astrophysical environments. In the circumgalactic medium (CGM) and the intracluster medium (ICM), it is expected that relativistic cosmic rays collide with thermal particles and produce $\gamma$-rays through pion decay. The $\gamma$-ray luminosity of a plasma depends on where cosmic rays are: if they are in denser gas, they produce more $\gamma$-rays. In this work, we study how different cosmic-ray transport mechanisms impact the $\gamma$-ray luminosity of a turbulent, multiphase medium formed from an initially diffuse medium. Two quantities set the luminosity: the average cosmic-ray energy density and the correlation of cosmic-ray energy and gas density. Overall, cosmic rays must escape cold dense regions in order to produce less $\gamma$-ray emission and be consistent with observations. Our simulations with fast transport mechanisms (either diffusion or streaming) are degenerate: they each produce a lower $\gamma$-ray luminosity than slow transport simulations by two orders of magnitude. This result means that fast transport (particularly in dense clumps) is necessary for simulations to agree with the dearth of observations of $\gamma$-ray emission from diffuse gas like the CGM and ICM. We also show the significant difference in luminosity is the result of cosmic-ray reacceleration. This reacceleration is different from the turbulent reacceleration described by Ptuskin (1988). Instead, condensing, cold clouds drive a significant increase in the average cosmic-ray energy and, as a result, the $\gamma$-ray luminosity.

astro-ph.GA

Probing viscosity of the intracluster medium using ram-pressure stripping

Galaxies falling into galaxy clusters can leave imprints on both the corona of galaxies and the intracluster medium (ICM) of galaxy clusters. Throughout this infall process, the galaxy's atmosphere is subjected to ram pressure from a headwind, leading to the stripping morphology observed in its tail. The morphological evolution is affected by the properties of the surrounding ICM such as magnetic fields and viscosity. In this Letter, we perform 3D Braginskii-magnetohydrodynamic simulations using the FLASH code with varied ICM viscosity models. Specifically, we explore four models: an inviscid case, unsuppressed isotropic viscosity, unsuppressed anisotropic viscosity, and anisotropic viscosity suppressed by plasma instabilities. Our findings indicate that the isotropic viscosity case effectively suppresses hydrodynamic instabilities and shows strong viscous heating and the least mixing with the ICM, enabling the formation of long, coherent tails. The inviscid model has the shortest tail due to vigorous mixing, and the models with anisotropic viscosity are in between. The model with suppressed anisotropic viscosity due to plasma instabilities exhibits enhanced turbulence in the galactic tail and a concurrent limitation in viscous heating compared to the model neglecting plasma instabilities. These findings highlight the significant impact of ICM plasma physics on the processes of ram pressure stripping of galaxies.

astro-ph.GA

Resolving Star Cluster Formation in Galaxy Simulations with Cosmic Ray Feedback

Star clusters host the massive stars responsible for feedback in star-forming galaxies. Stellar feedback shapes the interstellar medium (ISM), affecting the formation of future star clusters. To self-consistently capture the interplay between feedback and star formation, a model must resolve the parsec-scale star formation sites and the multiphase ISM. Additionally, the dynamical impact of cosmic rays (CRs) on star formation rates (SFRs) must also be considered. We present the first simulations of the formation of an ensemble of star clusters with dynamically-coupled CRs, near-individual star particles, and a feedback-regulated ISM. We analyze tallbox simulations performed using the CRISP model in the moving-mesh code AREPO. We apply varied implementations of CR transport under the theory of self-confinement. We find that CRs simultaneously reduce the SFR, the power law slope of the cluster mass function, and the cluster formation efficiency. Each simulation is compatible with observations, and CR feedback tends to move results along observed star cluster relations. We see only modest changes in cluster radius and velocity dispersions, but significant differences in the virial parameters. Ultimately, the primary impact of CRs is to reduce SFRs. Lower SFRs imply fewer supernovae, and consequently a lower turbulent energy budget for gas. Star clusters formed in a CR-regulated ISM have lower velocity dispersions, and are therefore more bound under self-gravity. The effective clustering of supernovae is unchanged by CRs. Despite the idealized setup, the CRISP feedback model recovers many key aspects of star cluster formation.

astro-ph.GA

Robust magnetic field estimates in star-forming galaxies with the equipartition formula in the absence of equipartition

The equipartition model is widely used to estimate magnetic field strength from synchrotron intensity in radio galaxies, yet the validity of its underlying assumptions remains uncertain. Using an Arepo simulation which incorporates a two-moment cosmic ray (CR) transport scheme and a multiphase interstellar medium, we compare magnetic fields inferred from synthetic synchrotron emission maps with the true fields in the simulation. Starting from the derivation of the equipartition formula, we find that the deviation between the equipartition magnetic field and the true magnetic field depends only weakly on the ratio of the magnetic to the CR energy density. In practice, for both face-on and edge-on projections, the equipartition model slightly overestimates the total synchrotron-weighted magnetic field with mean offsets of 32% (0.17 dex) and 36% (0.2 dex), even though the energy equipartition between CR protons and magnetic fields does not hold locally. Beyond these average offsets, a clear trend emerges in edge-on projections that the model underestimates the field in the disk and overestimates it in the halo. Our results demonstrate that the validity of the equipartition model depends only weakly on the strict fulfillment of energy equipartition, and that the equipartition model remains a practical method for estimating magnetic field strengths in face-on projection maps based on our CR-magnetohydrodynamics simulation.

astro-ph.GA

Magnetic fields in the intracluster medium with TNG-Cluster: properties, morphology, and tangential anisotropy

We characterize the magnetic field properties of 352 massive galaxy clusters from the TNG-Cluster magnetohydrodynamical cosmological simulation with a focus on central magnetic field morphology in cool-core (CC) vs non-cool-core (NCC) clusters. We present the central values and radial profiles of magnetic field strength and plasma parameter as a function of mass, cooling status and redshift. Compared to low-redshift observations, TNG-Cluster produces reasonable magnetic field amplitudes in the central regions of clusters spanning a range of 1-200 muG. We then discuss the main finding of this work: z=0 cool-core clusters have preferentially tangential magnetic fields at a characteristic scale of ~ 0.1 r500c. These strongly tangential field orientations are specific to CCs. In contrast, across the full cluster population, magnetic fields show isotropic configurations at all radii and redshifts. As individual halos grow, the evolution of their magnetic field topologies is diverse: tangential features can be short-lived, persist over large cosmological time-scales, or periodically appear, vanish, and reappear towards z=0. We discuss the underlying physics and possible physical scenarios to explain the origin of these structures. We argue that both AGN feedback-driven outflows, and merger-driven sloshing motions, cannot explain the population-wide tangential bias in magnetic field orientation. Instead, we propose that the trapping of internal gravity waves is responsible for the tangentially biased magnetic field topologies that we find in cool-core TNG-Cluster halos, due to the strong entropy gradient in these clusters.

astro-ph.GA

Cosmic Ray-Driven Galactic Winds with Resolved ISM and Ion-Neutral Damping

Feedback processes in galaxies dictate their structure and evolution. Baryons can be cycled through stars, which inject energy into the interstellar medium (ISM) in supernova explosions, fueling multiphase galactic winds. Cosmic rays (CRs) accelerated at supernova remnants are an important component of feedback. CRs can effectively contribute to wind driving; however, their impact heavily depends on the assumed CR transport model. We run high-resolution "tallbox" simulations of a patch of a galactic disk using the moving mesh magnetohydrodynamics code AREPO, including varied CR implementations and the CRISP non-equilibrium thermochemistry model. We characterize the impact of CR feedback on star formation and multiphase outflows. While CR-driven winds are able to supply energy to a global-scale wind, a purely thermal wind loses most of its energy by the time it reaches 3 kpc above the disk midplane. We further find that the adopted CR transport model significantly affects the steady-state of the wind. In the model with CR advection, streaming, diffusion, and nonlinear Landau damping, CRs provide very strong feedback. Additionally accounting for ion-neutral damping (IND) decouples CRs from the cold ISM, which reduces the impact of CRs on the star formation rate. Nevertheless, CRs in this most realistic model are able to accelerate warm gas and levitate cool gas in the wind but have little effect on cold gas and hot gas. This model displays moderate mass loading and significant CR energy loading, demonstrating that IND does not prevent CRs from providing effective feedback.

astro-ph.GA

Simulating Radio Synchrotron Morphology, Spectra, and Polarization of Cosmic Ray Driven Galactic Winds

The formation of galaxies is significantly influenced by galactic winds, possibly driven by cosmic rays due to their long cooling times and better coupling to plasma compared to radiation. In this study, we compare the radio observations of the edge-on galaxy NGC 4217 from the CHANG-ES collaboration catalog with a mock observation of an isolated galaxy based on the arepo simulation that adopts the state-of-the-art two-moment cosmic ray transport treatment and multiphase interstellar medium model. We find significant agreement between the simulated and observed images and spectroscopic data for reasonable model parameters. Specifically, we find that (i) the shape of the intensity profiles depends weakly on the magnitude of the magnetic field, the distance of the simulated galaxy, and the normalization of the CR electron spectrum. The agreement between the mock and actual observations is degenerate with respect to these factors; (ii) the multi-wavelength spectrum above 0.1 GHz is in agreement with the radio observations and its slope is also only weakly sensitive to the magnetic field strength; (iii) the magnetic field direction exhibits X-shaped morphology, often seen in edge-on galaxies, which is consistent with the observations and indicates the presence of a galactic-scale outflow. Our results highlight the importance of incorporating advanced cosmic ray transport models in simulations and provide a deeper understanding of galactic wind dynamics and its impact on galaxy evolution.

astro-ph.GA

On the Origin of the Ancient, Large-Scale Cold Front in the Perseus Cluster of Galaxies

The intracluster medium of the Perseus Cluster exhibits spiral-shaped X-ray surface brightness discontinuities known as ``cold fronts'', which simulations indicate are caused by the sloshing motion of the gas after the passage of a subcluster. Recent observations of Perseus have shown that these fronts extend to large radii. In this work, we present simulations of the formation of sloshing cold fronts in Perseus using the AREPO magnetohydrodynamics code, to produce a plausible scenario for the formation of the large front at a radius of 700 kpc. Our simulations explore a range of subcluster masses and impact parameters. We find that low-mass subclusters cannot generate a cold front that can propagate to such a large radius, and that small impact parameters create too much turbulence which leads to the disruption of the cold front before it reaches such a large distance. Subclusters which make only one core passage produce a stable initial front that expands to large radii, but without a second core passage of the subcluster other fronts are not created at a later time in the core region. We find a small range of simulations with subclusters with mass ratios of $R \sim 1:5$ and initial impact parameter of $θ~\sim~20-25^\circ$ which not only produce the large cold front but a second set in the core region at later times. These simulations indicate that the ``ancient' cold front is $\sim$6-8.5 Gyr old. For the simulations providing the closest match with observations, the subcluster has completely merged into the main cluster.

astro-ph.HE

Cosmic ray feedback in galaxies and galaxy clusters -- A pedagogical introduction and a topical review of the acceleration, transport, observables, and dynamical impact of cosmic rays

Understanding the physical mechanisms that control galaxy formation is a fundamental challenge in contemporary astrophysics. Recent advances in the field of astrophysical feedback strongly suggest that cosmic rays (CRs) may be crucially important for our understanding of cosmological galaxy formation and evolution. The appealing features of CRs are their relatively long cooling times and relatively strong dynamical coupling to the gas. In galaxies, CRs can be close to equipartition with the thermal, magnetic, and turbulent energy density in the interstellar medium, and can be dynamically very important in driving large-scale galactic winds. Similarly, CRs may provide a significant contribution to the pressure in the circumgalactic medium. In galaxy clusters, CRs may play a key role in addressing the classic cooling flow problem by facilitating efficient heating of the intracluster medium and preventing excessive star formation. Overall, the underlying physics of CR interactions with plasmas exhibit broad parallels across the entire range of scales characteristic of the interstellar, circumgalactic, and intracluster media. Here we present a review of the state-of-the-art of this field and provide a pedagogical introduction to cosmic ray plasma physics, including the physics of wave-particle interactions, acceleration processes, CR spatial and spectral transport, and important cooling processes. The field is ripe for discovery and will remain the subject of intense theoretical, computational, and observational research over the next decade with profound implications for the interpretation of the observations of stellar and supermassive black hole feedback spanning the entire width of the electromagnetic spectrum and multi-messenger data.

astro-ph.HE

Line Emission Mapper (LEM): Probing the physics of cosmic ecosystems

The Line Emission Mapper (LEM) is an X-ray Probe for the 2030s that will answer the outstanding questions of the Universe's structure formation. It will also provide transformative new observing capabilities for every area of astrophysics, and to heliophysics and planetary physics as well. LEM's main goal is a comprehensive look at the physics of galaxy formation, including stellar and black-hole feedback and flows of baryonic matter into and out of galaxies. These processes are best studied in X-rays, and emission-line mapping is the pressing need in this area. LEM will use a large microcalorimeter array/IFU, covering a 30x30' field with 10" angular resolution, to map the soft X-ray line emission from objects that constitute galactic ecosystems. These include supernova remnants, star-forming regions, superbubbles, galactic outflows (such as the Fermi/eROSITA bubbles in the Milky Way and their analogs in other galaxies), the Circumgalactic Medium in the Milky Way and other galaxies, and the Intergalactic Medium at the outskirts and beyond the confines of galaxies and clusters. LEM's 1-2 eV spectral resolution in the 0.2-2 keV band will make it possible to disentangle the faintest emission lines in those objects from the bright Milky Way foreground, providing groundbreaking measurements of the physics of these plasmas, from temperatures, densities, chemical composition to gas dynamics. While LEM's main focus is on galaxy formation, it will provide transformative capability for all classes of astrophysical objects, from the Earth's magnetosphere, planets and comets to the interstellar medium and X-ray binaries in nearby galaxies, AGN, and cooling gas in galaxy clusters. In addition to pointed observations, LEM will perform a shallow all-sky survey that will dramatically expand the discovery space.

astro-ph.IM

Stress-Testing Cosmic Ray Physics: The Impact of Cosmic Rays on the Surviving Disk of Ram Pressure Stripped Galaxies

Cluster spiral galaxies suffer catastrophic losses of the cool, neutral gas component of their interstellar medium due to ram pressure stripping, contributing to the observed quenching of star formation in the disk compared to galaxies in lower density environments. However, the short term effects of ram pressure on the star formation rate and AGN activity of galaxies undergoing stripping remain unclear. Numerical studies have recently demonstrated cosmic rays can dramatically influence galaxy evolution for isolated galaxies, yet their influence on ram pressure stripping remains poorly constrained. We perform the first cosmic-ray magneto-hydrodynamic simulations of an $L_{*}$ galaxy undergoing ram pressure stripping, including radiative cooling, self-gravity of the gas, star formation, and stellar feedback. We find the microscopic transport of cosmic rays plays a key role in modulating the star formation enhancement experienced by spirals at the outskirts of clusters compared to isolated spirals. Moreover, we find that galaxies undergoing ram pressure stripping exhibit enhanced gas accretion onto their centers, which may explain the prevalence of AGN in these objects. In agreement with observations, we find cosmic rays significantly boost the global radio emission of cluster spirals. Although the gas removal rate is relatively insensitive to cosmic ray physics, we find that cosmic rays significantly modify the phase distribution of the remaining gas disk. These results suggest observations of galaxies undergoing ram pressure stripping may place novel constraints on cosmic-ray calorimetry and transport.

astro-ph.GA

Chaotic cold accretion in giant elliptical galaxies heated by AGN cosmic rays

Black hole feedback plays a central role in shaping the circumgalactic medium (CGM) of elliptical galaxies. We systematically study the impact of plasma physics on the evolution of ellipticals by performing three-dimensional non-ideal magneto-hydrodynamic simulations of the interactions of active galactic nucleus (AGN) jets with the CGM including magnetic fields, and cosmic rays (CRs) and their transport processes. We find that the physics of feedback operating on large galactic scales depends very sensitively on plasma physics operating on small scales. Specifically, we demonstrate that: (i) in the purely hydrodynamical case, the AGN jets initially maintain the atmospheres in global thermal balance. However, local thermal instability generically leads to the formation of massive cold disks in the vicinity of the central black hole in disagreement with observations; (ii) including weak magnetic fields prevents the formation of the disks because local B-field amplification in the precipitating cold gas leads to strong magnetic breaking, which quickly extracts angular momentum from the accreting clouds. The magnetic fields transform the cold clouds into narrow filaments that do not fall ballistically; (iii) when plasma composition in the AGN jets is dominated by CRs, and CR transport is neglected, the atmospheres exhibit cooling catastrophes due to inefficient heat transfer from the AGN to CGM despite Coulomb/hadronic CR losses being present; (iv) including CR streaming and heating restores agreement with the observations, i.e., cooling catastrophes are prevented and massive cold central disks do not form. The AGN power is reduced as its energy is utilized efficiently.

astro-ph.GA

Supermassive Black Hole Feedback

Understanding the processes that drive galaxy formation and shape the observed properties of galaxies is one of the most interesting and challenging frontier problems of modern astrophysics. We now know that the evolution of galaxies is critically shaped by the energy injection from accreting supermassive black holes (SMBHs). However, it is unclear how exactly the physics of this feedback process affects galaxy formation and evolution. In particular, a major challenge is unraveling how the energy released near the SMBHs is distributed over nine orders of magnitude in distance throughout galaxies and their immediate environments. The best place to study the impact of SMBH feedback is in the hot atmospheres of massive galaxies, groups, and galaxy clusters, which host the most massive black holes in the Universe, and where we can directly image the impact of black holes on their surroundings. We identify critical questions and potential measurements that will likely transform our understanding of the physics of SMBH feedback and how it shapes galaxies, through detailed measurements of (i) the thermodynamic and velocity fluctuations in the intracluster medium (ICM) as well as (ii) the composition of the bubbles inflated by SMBHs in the centers of galaxy clusters, and their influence on the cluster gas and galaxy growth, using the next generation of high spectral and spatial resolution X-ray and microwave telescopes.

astro-ph.HE

Physics of cosmic plasmas from high angular resolution X-ray imaging of galaxy clusters

Galaxy clusters are massive dark matter-dominated systems filled with X-ray emitting, optically thin plasma. Their large size and relative simplicity (at least as astrophysical objects go) make them a unique laboratory to measure some of the interesting plasma properties that are inaccessible by other means but fundamentally important for understanding and modeling many astrophysical phenomena -- from solar flares to black hole accretion to galaxy formation and the emergence of the cosmological Large Scale Structure. While every cluster astrophysicist is eagerly anticipating the direct gas velocity measurements from the forthcoming microcalorimeters onboard XRISM, Athena and future missions such as Lynx, a number of those plasma properties can best be probed by high-resolution X-ray imaging of galaxy clusters. Chandra has obtained some trailblazing results, but only grazed the surface of such studies. In this white paper, we discuss why we need arcsecond-resolution, high collecting area, low relative background X-ray imagers (with modest spectral resolution), such as the proposed AXIS and the imaging detector of Lynx.

astro-ph.HE