Recently, Suzaku has produced temperature and entropy profiles, along with profiles of gas density, gas fraction, and mass, for multiple galaxy clusters out to ~r_200 (~= virial radius). In this paper, we compare these novel X-ray observations with results from N-body + hydrodynamic adaptive mesh refinement cosmological simulations using the Enzo code. There is excellent agreement in the temperature, density, and entropy profiles between a sample of 27 mostly substructure-free massive clusters in the simulated volume and the observed clusters. This supports our previous contention that clusters have "universal" outer temperature profiles. Furthermore, it appears that the simplest adiabatic gas physics used in these Enzo simulations is adequate to model the outer regions of these clusters without other mechanisms (e.g., non-gravitational heating, cooling, magnetic fields, or cosmic rays). However, the outskirts of these clusters are not in hydrostatic equilibrium. There is significant bulk flow and turbulence in the outer intracluster medium created by accretion from filaments. Thus, the gas is not fully supported by thermal pressure. The implications for mass estimation from X-ray data are discussed.
Some observations such as those presented in Walker et al. show that the observed entropy profiles of the intra-cluster medium (ICM) deviate from the power-law prediction of adiabatic simulations. This implies that non-gravitational processes, which are absent in the simulations, may be important in the evolution of the ICM, and by quantifying the deviation, we may be able to estimate the feedback energy in the ICM and use it as a probe of the non-gravitational processes. To address this issue we calculate the ICM entropy profiles in a sample of 47 galaxy clusters and groups, which have been o…
We investigate the relationship between the turnaround radius ($R_t$) and the virial mass ($M_v$) of cosmic structures in the context of $Λ$CDM model and in an $f(R)$ model of modified gravity -- namely, the Hu-Sawicki model. The $R_t$ is the distance from the center of the cosmic structure to the shell that is detaching from the Hubble flow at a given time, while the $M_v$ is defined, for this work, as the mass enclosed within the volume where the density is $200$ times the background density. We consider that gravitationally bound astrophysical systems follow a Navarro-Frenk-White density pr…
Using cosmological galaxy formation simulations from the MaGICC project, spanning more than three magnitudes in stellar mass (~10^7-3x10^{10} Msun), we trace the baryonic cycle of infalling gas from the virial radius through to its participation in the star formation process. An emphasis is placed upon the temporal history of chemical enrichment during its passage through the corona and CGM. We derive the distributions of time between gas crossing the virial radius and being accreted to the star forming region (which allows mixing within the corona), as well as the time between gas being accre…
Entropy is an advantageous diagnostics to study the thermodynamic history of the intracluster plasma of galaxy clusters. We present the entropy profile of the Abell 2244 galaxy cluster derived both exclusively using X-ray data from the low-background Swift XRT telescope and also using Planck y data. The entropy profile derivation using X-rays only is robust at least to the virial radius because the cluster brightness is large compared to the X-ray background at low energies, temperature is strongly bounded by the lack of cluster X-ray photons at energies kT>3 keV, and the XRT background is low…
We use particle data from the Illustris simulation, combined with individual kinematic constraints on the mass of the Milky Way (MW) at specific distances from the Galactic center, to infer the radial distribution of the MW's dark matter halo mass. Our method allows us to convert any constraint on the mass of the MW within a fixed distance to a full circular velocity profile to the MW's virial radius. As primary examples, we take two recent (and discrepant) measurements of the total mass within 50 kpc of the Galaxy and find they imply very different mass profiles and stellar masses for the Gal…
We present joint Suzaku and Chandra observations of MKW4. With a global temperature of 1.6 keV, MKW4 is one of the smallest galaxy groups that have been mapped in X-rays out to the virial radius. We measure its gas properties from its center to the virial radius in the north, east, and northeast directions. Its entropy profile follows a power-law of $\propto r^{1.1}$ between R$_{500}$ and R$_{200}$ in all directions, as expected from the purely gravitational structure formation model. The well-behaved entropy profiles at the outskirts of MKW4 disfavor the presence of gas clumping or thermal no…
We consider the dynamics in and near galaxy clusters. Gas, dark matter and galaxies are presently falling into the clusters between approximately 1 and 5 virial radii. At very large distances, beyond 10 virial radii, all matter is following the Hubble flow, and inside the virial radius the matter particles have on average zero radial velocity. The cosmological parameters are imprinted on the infall profile of the gas, however, no method exists, which allows a measurement of it. We consider the results of two cosmological simulations (using the numerical codes RAMSES and Gadget) and find that t…
The baryon content around local galaxies is observed to be much less than is needed in Big Bang nucleosynthesis. Simulations indicate that a significant fraction of these "missing baryons" may be stored in a hot tenuous circum-galactic medium (CGM) around massive galaxies extending to or even beyond the virial radius of their dark matter halos. Previous observations in X-ray and Sunyaev-Zel'dovich (SZ) signal claimed that $\sim(1-50)\%$ of the expected baryons are stored in a hot CGM within the virial radius. The large scatter is mainly caused by the very uncertain extrapolation of the hot gas…
Chameleon gravity is an example of a model that gives rise to interesting phenomenology on cosmological scales while simultaneously possessing a screening mechanism, allowing it to avoid solar system constraints. Such models result in non-linear field equations, which can be solved analytically only in simple highly symmetric systems. In this work we study the equation of motion of a scalar-tensor theory with chameleon screening using the finite element method. More specifically, we solve the field equation for spherical and triaxial NFW cluster-sized halos. This allows a detailed investigatio…
Aims. This work considers the Virgo cluster of galaxies, focusing on its structure, kinematics, and morphological landscape. Our principal aim is to estimate the virial mass of the cluster. For this purpose, we present a sample of 1537 galaxies with radial velocities $V_{LG} < 2600$~km~s$^{-1}$ situated within a region of $ΔSGL = 30^\circ$ and $ΔSGB = 20^\circ$ around M87. About half of the galaxies have distance estimates. Methods. We selected 398 galaxies with distances in a $(17\pm5)$~Mpc range. Based on their 1D and 2D number-density profiles and their radial velocity dispersions, we made …
In this second paper on the entire virial region of the relaxed fossil cluster RXJ1159+5531, we present a hydrostatic analysis of the hot intracluster medium (ICM). For a model consisting of ICM, stellar mass from the central galaxy (BCG), and an NFW dark matter (DM) halo, we obtain good descriptions of the projected radial profiles of ICM emissivity and temperature. The BCG stellar mass is clearly detected with M_star/L_K = 0.61 +/- 0.11 solar, consistent with stellar population synthesis models for a Milky-Way IMF. We obtain a halo concentration, c_200 =8.4 +/- 1.0, and virial mass, M_200 = …
We study the internal kinematics of galaxy clusters in the region beyond the sphere of virialization. Galaxies around a virialized cluster are infalling towards the cluster centre with a non-zero mean radial velocity. We develop a new formalism for describing the dynamical state of clusters, by generalizing the standard Jeans formalism with the inclusion of the peculiar infall motions of galaxies and the Hubble expansion as well as the contributions due to background cosmology. Using empirical fits to the radial profiles of density, mean radial velocity and velocity anisotropy of both a stacke…
Virial shocks around galaxy clusters are expected to show a cutoff in the thermal Sunyaev-Zel'dovich (SZ) signal, coincident with a leptonic ring. However, until now, leptonic virial signals were reported only in Coma and in stacked Fermi-LAT clusters, and an SZ virial shock signal was reported only in A2319. We point out that a few clusters --- presently Coma, A2319, and A2142 --- already show a sharp drop in Planck SZ pressure near the virial radius, coincident with a weak LAT $γ$-ray excess. These signatures are shown to trace the virial shocks of the clusters, at joint medium to high confi…
Context: The shape of the mass density profiles of cosmological halos informs us of the nature of DM and DM-baryons interactions. Previous estimates of the inner slope of the mass density profiles of clusters of galaxies are in opposition to predictions derived from numerical simulations of CDM. Aims: We determine the inner slope of the DM density profile of a massive cluster of galaxies, Abell S1063 (RXC J2248.7$-$4431) at $z=0.35$, with a dynamical analysis based on an extensive spectroscopic campaign carried out with the VIMOS and MUSE spectrographs at the ESO VLT. This new data set provide…
Euclid: Early Release Observations. A combined strong and weak lensing solution for Abell 2390 beyond its virial radius
Instituto de Física de Cantabria（坎塔布里亚物理研究所）；Institute for Astronomy, University of Edinburgh（爱丁堡大学天文研究所）；Aix-Marseille Université, CNRS, CNES, LAM（艾克斯-马赛大学）；Institut d’Astrophysique de Paris, UMR 7095, CNRS, and Sorbonne Université（巴黎天体物理学研究所）；Universität Innsbruck, Institut für Astro- und Teilchenphysik（因斯布鲁克大学）；Department of Physics and Astronomy, University of Pennsylvania（宾夕法尼亚大学物理与天文学系）；Department of Astronomy, University of Massachusetts（马萨诸塞大学天文学系）；Department of Astronomy, University of Geneva（日内瓦大学天文学系）；STAR Institute, University of Liège（列日大学STAR研究所）；Department of Physics, Centre for Extragalactic Astronomy, Durham University（杜伦大学）
The limits of feedback from active galactic nuclei
Institute for Computational Cosmology, Department of Physics, Durham University（达勒姆大学物理学院计算宇宙学研究所）；Institute of Astronomy and Kavli Institute for Cosmology, University of Cambridge（剑桥大学天体物理与卡弗里宇宙学研究所）；Cavendish Laboratory, Department of Physics, University of Cambridge（剑桥大学物理学院卡文迪许实验室）；The Oskar Klein Centre, Department of Physics, Stockholm University（斯德哥尔摩大学物理学院奥斯卡·克莱因中心）；Leiden Observatory, Leiden University（莱顿大学莱顿天文台）；Lorentz Institute for Theoretical Physics, Leiden University（莱顿大学洛伦兹理论物理研究所）
Context. Galaxy clusters are continuously growing through the accretion of matter in their outskirts. This process induces inhomogeneities in the gas density distribution (clumping) which need to be taken into account to recover the physical properties of the intracluster medium (ICM) at large radii. Aims. We studied the thermodynamic properties in the outskirts (R > R500) of the massive galaxy cluster Abell 2142 by combining the Sunyaev Zel'dovich (SZ) effect with the X-ray signal. Methods. We combined the SZ pressure profile measured by Planck with the XMM-Newton gas density profile to recov…
We study the impact of cosmic rays (CRs) on the structure of virial shocks, using a large suite of high-resolution cosmological FIRE-2 simulations accounting for CR injection by supernovae. In massive ($M_{\rm halo} \gtrsim 10^{11}\,M_{\odot}$), low-redshift ($z\lesssim 1-2$) halos, which are expected to form "hot halos" with slowly-cooling gas in quasi-hydrostatic equilibrium (with a stable virial shock), our simulations without CRs do exhibit clear virial shocks. The cooler phase condensing out from inflows becomes pressure-confined to over-dense clumps, embedded in low-density, volume-filli…
We measure for the first time the outermost edges of the Milky Way (MW) halo in terms of the depletion and turnaround radii. The inner depletion radius, $r_\mathrm{id}$, identified at the location of maximum infall velocity, separates a growing halo from the draining environment, while the turnaround radius, $r_\mathrm{ta}$, marks the outermost edge of infalling material towards the halo, both of which are located well outside the virial radius. Using the motions of nearby dwarf galaxies within $3\mathrm{Mpc}$, we obtain a marginal detection of the infall zone around the MW with a maximum velo…
The topology of the magnetic field in Abell 2255 out to its virial radius. Results from the LOFAR Galaxy Cluster Ultra-Deep Field
INAF - IRA（意大利国家天体物理研究所-博洛涅分院）；Leiden Observatory, Leiden University（莱顿大学莱顿天文台）；Institute for Advanced Study（普林斯顿高等研究院）；Dipartimento di Fisica e Astronomia, Università di Bologna（博洛尼亚大学物理与天文学系）；Center for Astrophysics Harvard & Smithsonian（哈佛&史密森尼天体物理中心）；Department of Astronomy, University of Wisconsin-Madison（威斯康星大学麦迪逊分校天文学系）；ASTRON, the Netherlands Institute for Radio Astronomy（荷兰射电天文研究所）；Hamburger Sternwarte, Universität Hamburg（汉堡大学汉堡天文台）；INAF - IASF Milano（意大利国家天体物理研究所-米兰天文物理研究所）
Max-Planck-Institut für Astrophysik（马克斯·普朗克天体物理研究所）；University College London（伦敦大学学院）；Stockholm University（斯德哥尔摩大学）；Fermi National Accelerator Laboratory（费米国家加速器实验室）；University of Chicago（芝加哥大学）；Science and Technology Facilities Council（科学与技术设施委员会）；Rutherford Appleton Laboratory（卢瑟福·阿普尔顿实验室）
The density profiles of dark matter halos are typically modeled using empirical formulae fitted to the density profiles of relaxed halo populations. We present a neural network model that is trained to learn the mapping from the raw density field containing each halo to the dark matter density profile. We show that the model recovers the widely-used Navarro-Frenk-White (NFW) profile out to the virial radius, and can additionally describe the variability in the outer profile of the halos. The neural network architecture consists of a supervised encoder-decoder framework, which first compresses …
