It is now widely accepted that heating processes play a fundamental role in galaxy clusters, struggling in an intricate but fascinating `dance' with its antagonist, radiative cooling. Last generation observations, especially X-ray, are giving us tiny hints about the notes of this endless ballet. Cavities, shocks, turbulence and wide absorption-lines indicate the central active nucleus is injecting huge amount of energy in the intracluster medium. However, which is the real dominant engine of self-regulated heating? One of the model we propose are massive subrelativistic outflows, probably generated by a wind disc or just the result of the entrainment on kpc scale by the fast radio jet. Using a modified version of AMR code FLASH 3.2, we explored several feedback mechanisms which self-regulate the mechanical power. Two are the best schemes that answer our primary question, id est quenching cooling flow and at the same time preserving a cool core appearance for a long term evolution (7 Gyr): one more explosive (with efficiencies 0.005 - 0.01), triggered by central cooled gas, and the other gentler, ignited by hot gas Bondi accretion (with efficiency 0.1). These three-dimensional simulations show that the total energy injected is not the key aspect, but the results strongly depend on how energy is given to the ICM. We follow the dynamics of best model (temperature, density, SB maps and profiles) and produce many observable predictions: buoyant bubbles, ripples, turbulence, iron abundance maps and hydrostatic equilibrium deviation. We present a deep discussion of merits and flaws of all our models, with a critical eye towards observational concordance.
We develop a new sub-grid model for the growth of supermassive Black Holes (BHs) and their associated Active Galactic Nuclei (AGN) feedback in hydrodynamical cosmological simulations. Assuming that BHs are created in the early stages of galaxy formation, they grow by mergers and accretion of gas at a Eddington-limited Bondi accretion rate. However this growth is regulated by AGN feedback which we model using two different modes: a quasar-heating mode when accretion rates onto the BHs are comparable to the Eddington rate, and a radio-jet mode at lower accretion rates. In other words, our feedba…
AGN heating, through massive subrelativistic outflows, might be the key to solve the long-lasting `cooling flow problem' in cosmological systems. In a previous paper, we showed that cold accretion feedback and, to a lesser degree, Bondi self-regulated models are in fact able to quench cooling rates for several Gyr, at the same time preserving the mainc ool core features, like observed density and temperature profiles. Is it true also for lighter systems, such as galaxy groups? The answer is globally yes, although with remarkable differences. Adopting a modified version of the AMR code FLASH 3.…
We consider the problem of self-regulated heating and cooling in galaxy clusters and the implications for cluster magnetic fields and turbulence. Viscous heating of a weakly collisional magnetised plasma is regulated by the pressure anisotropy with respect to the local direction of the magnetic field. The intracluster medium is a high-beta plasma, where pressure anisotropies caused by the turbulent stresses and the consequent local changes in the magnetic field will trigger very fast microscale instabilities. We argue that the net effect of these instabilities will be to pin the pressure aniso…
Supermassive black hole accretion and feedback play central role in the evolution of galaxies, groups, and clusters. I review how AGN feedback is tightly coupled with the formation of multiphase gas and the newly probed chaotic cold accretion (CCA). In a turbulent and heated atmosphere, cold clouds and kpc-scale filaments condense out of the plasma via thermal instability and rain toward the black hole. In the nucleus, the recurrent chaotic collisions between the cold clouds, filaments, and central torus promote angular momentum cancellation or mixing, boosting the accretion rate up to 100 tim…
We present the first implementation of Active Galactic Nuclei (AGN) feedback in the form of momentum driven jets in an Adaptive Mesh Refinement (AMR) cosmological resimulation of a galaxy cluster. The jets are powered by gas accretion onto Super Massive Black Holes (SMBHs) which also grow by mergers. Throughout its formation, the cluster experiences different dynamical states: both a morphologically perturbed epoch at early times and a relaxed state at late times allowing us to study the different modes of BH growth and associated AGN jet feedback. BHs accrete gas efficiently at high redshift …
In cool-core galaxy clusters with central cooling times much shorter than a Hubble time, condensation of the ambient central gas is regulated by a heating mechanism, probably an active galactic nucleus (AGN). Previous analytical work has suggested that certain radial distributions of heat input may result in convergence to a quasi-steady global state that does not substantively change on the timescale for radiative cooling, even if the heating and cooling are not locally in balance. To test this hypothesis, we simulate idealized galaxy cluster halos using the \ENZO code with an idealized, sphe…
The radiative cooling timescales at the centers of hot atmospheres surrounding elliptical galaxies, groups, and clusters are much shorter than their ages. Therefore, hot atmospheres are expected to cool and to form stars. Cold gas and star formation are observed in central cluster galaxies but at levels below those expected from an unimpeded cooling flow. X-ray observations have shown that wholesale cooling is being offset by mechanical heating from radio active galactic nuclei. Feedback is widely considered to be an important and perhaps unavoidable consequence of the evolution of galaxies an…
The absence of large cooling flows in cool core clusters appears to require self-regulated energy feedback by active galactic nuclei (AGNs) but the exact heating mechanism has not yet been identified. Here, we analyse whether a combination of cosmic ray (CR) heating and thermal conduction can offset radiative cooling. To this end, we compile a large sample of 39 cool core clusters and determine steady state solutions of the hydrodynamic equations that are coupled to the CR energy equation. We find solutions that match the observed density and temperature profiles for all our clusters well. Rad…
Heating from active galactic nuclei (AGN) is thought to stabilize cool-core clusters, limiting star formation and cooling flows. We employ radiative magneto-hydrodynamic (MHD) simulations to model light AGN jet feedback with different accretion modes (Bondi-Hoyle-Lyttleton and cold accretion) in an idealised Perseus-like cluster. Independent of the probed accretion model, accretion efficiency, jet density and resolution, the cluster self-regulates with central entropies and cooling times consistent with observed cool-core clusters in this non-cosmological setting. We find that increased jet ef…
Feedback processes are thought to solve some of the long-standing issues of the numerical modelling of galaxy formation: over-cooling, low angular momentum, massive blue galaxies, extra-galactic enrichment, etc. The accretion of gas onto super-massive black holes in the centre of massive galaxies can release tremendous amounts of energy to the surrounding medium. We show, with cosmological Adaptive Mesh Refinement simulations, how the growth of black holes is regulated by the feedback from Active Galactic Nuclei using a new dual jet/heating mechanism. We discuss how this large amount of feedba…
Star formation rates in the centers of disk galaxies often vastly exceed those at larger radii. We investigate the idea that these central starbursts are self-regulated, with the momentum flux injected to the ISM by star formation balancing the gravitational force confining the gas. For most starbursts, supernovae are the largest contributor to the momentum flux, and turbulence provides the main pressure support for the predominantly-molecular ISM. If the momentum feedback per stellar mass formed is p_*/m_* ~ 3000 km/s, the predicted star formation rate is Sigma_SFR=2 pi G Sigma^2 m_*/p_* ~0.1…
Self-regulated feedback by active galactic nuclei (AGNs) appears to be critical in balancing radiative cooling of the low-entropy gas at the centres of galaxy clusters and in regulating star formation in central galaxies. In a companion paper, we found steady-state solutions of the hydrodynamic equations that are coupled to the CR energy equation for a large cluster sample. In those solutions, radiative cooling in the central region is balanced by streaming CRs through the generation and dissipation of resonantly generated Alfv{é}n waves and by thermal conduction at large radii. Here we demons…
AGN outflows are the heat given up when gas in a galaxy evolves towards thermodynamic equilibrium. Indeed, while AGN feedback regulates the growth of massive galaxies, its origins can be understood as the spontaneous thermodynamic process which ensures that the (Gibbs) free energy of the system always decreases, enabling the galaxy to reach a more energetically favourable state. In particular, it is shown that feedback heating processes will be favoured whenever the hot atmosphere of a galaxy would effectively gain energy as a result of cooling. For example, as the hot atmosphere of a galaxy c…
The formation of supermassive black holes from Population III.1 seeds. IV. Self-regulated seeding from supermassive star ionizing feedback
Chalmers University of Technology（查尔姆斯理工大学）；INAF - Osservatorio Astronomico di Brera（意大利国家天体物理研究所布雷拉天文台）；University of Modena & Reggio Emilia（摩德纳与雷焦艾米利亚大学）；University of Oxford（牛津大学）；University of Memphis（孟菲斯大学）；Center for Astrophysics, Harvard and Smithsonian（哈佛史密松天体物理中心）；Università degli Studi di Trieste（的里雅斯特大学）；INAF - Osservatorio Astronomico di Trieste（意大利国家天体物理研究所的里雅斯特天文台）；INFN, Sezione di Trieste（意大利国家核物理研究所的里雅斯特分部）
Unopposed radiative cooling of plasma would lead to the cooling catastrophe, a massive inflow of condensing gas, manifest in the core of galaxies, groups and clusters. The last generation X-ray telescopes, Chandra and XMM, have radically changed our view on baryons, indicating AGN heating as the balancing counterpart of cooling. This work reviews our extensive investigation on self-regulated heating. We argue that the mechanical feedback, based on massive subrelativistic outflows, is the key to solving the cooling flow problem, i.e. dramatically quenching the cooling rates for several Gyr with…
It is commonly thought that AGN feedback can break the self-similar scaling relations of galaxies, groups, and clusters. Using high-resolution 3D hydrodynamic simulations, we isolate the impact of AGN feedback on the $L_{\rm x}-T_{\rm x} $ relation, testing the two archetypal and common regimes, self-regulated mechanical feedback and a quasar thermal blast. We find that AGN feedback has severe difficulty in breaking the relation in a consistent way. The similarity breaking is directly linked to the gas evacuation within $R_{500}$, while the central cooling times are inversely proportional to t…
This is the third in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Our sample comprises 40 clusters identified as being dynamically relaxed and hot (i.e., massive) in Papers I and II of this series. Here we consider the thermodynamics of the intracluster medium, in particular the profiles of density, temperature and related quantities, as well as integrated measurements of gas mass, average temperature, total luminosity and center-excluded luminosity. We fit power-law scaling relations of each of these quantities as a function of re…
The intracluster medium (ICM) is a multi-phase environment, dynamically regulated by Active Galactic Nuclei (AGN), the motions of galaxies through it, and mergers with other clusters. AGN as a central heating source are key to preventing runaway cooling flows, but their role in heating cores in a cosmological context is still poorly understood. The activity of the AGN is strongly linked to star formation, especially in the Brightest Cluster Galaxy (BCG), likely because both rely on cold phase gas. A self-consistent model for AGN and star formation in galaxy clusters thus requires cosmological …
The current generation of flagship X-ray missions, Chandra and XMM-Newton, has changed our understanding of the so-called "cool core" galaxy clusters and groups. Instead of the initial idea that the thermal gas is cooling and flowing toward the center, the new picture envisages a complex dynamical evolution of the intra-cluster medium (ICM) regulated by the radiative cooling and the nongravitational heating from the active galactic nucleus (AGN). Understanding the physics of the hot gas and its interplay with the relativistic plasma ejected by the AGN is key for understanding the growth and ev…
In several models of galaxy formation feedback occurs in cycles or mainly at high redshift. At times and in regions where feedback heating is ineffective, hot gas in the galaxy halo is expected to form a cooling flow, where the gas advects inward on a cooling timescale. Cooling flow solutions can thus be used as a benchmark for observations and simulations to constrain the timing and extent of feedback heating. Using analytic calculations and idealized 3D hydrodynamic simulations, we show that for a given halo mass and cooling function, steady-state cooling flows form a single-parameter family…
Cool cores of galaxy clusters are thought to be heated by low-power active galactic nuclei (AGN), whose accretion is regulated by feedback. However, the interaction between the hot gas ejected by the AGN and the ambient intracluster medium is extremely difficult to simulate, as it involves a wide range of spatial scales and gas that is Rayleigh-Taylor (RT) unstable. Here we use a subgrid model for RT-driven turbulence to overcome these problems and present the first observationally-consistent hydrodynamical simulations of AGN self-regulation in galaxy clusters. For a wide range of parameter ch…
Energy deposited by black holes in the hot X-ray gas of elliptical galaxies, groups and clusters
Observatoire de Paris, LUX, PSL University（巴黎天文台，LUX，巴黎文理研究大学）；INAF, Osservatorio di Astrofisica e Scienza dello Spazio（意大利国家天体物理研究所，空间天体物理与天体物理学观测站）；INFN, Sezione di Bologna（意大利国家核物理研究所，博洛尼部分部）
A Closer Look at the Dynamical State of the High-redshift Galaxy Cluster SPT-CL J2215-3537
Observatório Nacional（国家天文台）；Department of Astronomy, University of Michigan（密歇根大学天文学系）；Instituto de Astrofísica de Andalucía–CSIC（安达卢西亚天体物理研究所-西班牙国家研究委员会）
The hot plasma filling galaxy clusters emits copious X-ray radiation. The classic unheated and unperturbed cooling flow model predicts dramatic cooling rates and an isobaric X-ray spectrum with constant differential luminosity distribution. The observed cores of clusters (and groups) show instead a strong deficit of soft X-ray emission: $dL_{\rm x}/dT \propto (T/T_{\rm hot})^{α=2\pm1}$. Using 3D hydrodynamic simulations, we show that such deficit arises from the tight self-regulation between thermal instability condensation and AGN outflow injection: condensing clouds boost the AGN outflows, w…
We study the properties of ISM substructure and turbulence in hydrodynamic (AMR) galaxy simulations with resolutions up to 0.8 pc and 5x10^3 Msun. We analyse the power spectrum of the density distribution, and various components of the velocity field. We show that the disk thickness is about the average Jeans scale length, and is mainly regulated by gravitational instabilities. From this scale of energy injection, a turbulence cascade towards small-scale is observed, with almost isotropic small-scale motions. On scales larger than the disk thickness, density waves are observed, but there is al…
We present adaptive optics-assisted K-band integral field spectroscopy of the central cluster galaxy in 2A 0335+096 (z=0.0349). The H2 v=1-0 S(1) emission is concentrated in two peaks within 600 pc of the nucleus and fainter but kinematically-active emission extends towards the nucleus. The H2 is in a rotating structure which aligns with, and appears to have been accreted from, a stream of H-alpha emission extending over 14 kpc towards a companion galaxy. The projected rotation axis aligns with the 5 GHz radio lobes. This H2 traces the known 1.2E9 Msun CO-emitting reservoir; limits on the Br-g…
Multiwavelength data indicate that the X-ray emitting plasma in the cores of galaxy clusters is not cooling catastrophically. To large extent, cooling is offset by heating due to active galactic nuclei (AGN) via jets. The cool-core clusters, with cooler/denser plasmas, show multiphase gas and signs of some cooling in their cores. These observations suggest that the cool core is locally thermally unstable while maintaining global thermal equilibrium. Using high-resolution, three-dimensional simulations we study the formation of multiphase gas in cluster cores heated by highly-collimated bipolar…
Cosmic reionization by starlight from early galaxies affected their evolution, thereby impacting reionization, itself. Star formation suppression, for example, may explain the observed underabundance of Local Group dwarfs relative to N-body predictions for Cold Dark Matter. Reionization modelling requires simulating volumes large enough [~(100Mpc)^3] to sample reionization "patchiness", while resolving millions of galaxy sources above ~10^8 Msun , combining gravitational and gas dynamics with radiative transfer. Modelling the Local Group requires initial cosmological density fluctuations pre-s…
A fundamental gap in the current understanding of galaxies concerns the thermodynamical evolution of the ordinary, baryonic matter. On one hand, radiative emission drastically decreases the thermal energy content of the interstellar plasma (ISM), inducing a slow cooling flow toward the centre. On the other hand, the active galactic nucleus (AGN) struggles to prevent the runaway cooling catastrophe, injecting huge amount of energy in the ISM. The present study intends to deeply investigate the role of mechanical AGN feedback in (isolated or massive) elliptical galaxies, extending and completing…
