scholarly journals Generation and Implications of Post-Merger Turbulence in Clusters of Galaxies

1998 ◽  
Vol 188 ◽  
pp. 297-298
Author(s):  
I. Goldman
Keyword(s):  
Dark Matter ◽  
Galaxy Clusters ◽  
Gravitational Potential ◽  
Large Scale ◽  
Time Dependent ◽  
Clusters Of Galaxies ◽  
X Ray ◽  
Intracluster Gas ◽  
Detailed Work

Observations in X-ray and optical suggest that mergers of sub-clusters with galaxy clusters are quite common (for Coma see e.g., White et al. 1993; Colless & Dunn 1996; Ishizaka & Mineshige 1996). A merger leads to violent relaxation of the dissipationless dark matter resulting in a time-dependent gravitational potential. This in turn generates large-scale flows and shocks in the collisional baryonic intracluster gas (Takizawa & Mineshige 1997). Both the large scale flows and the shocks will excite turbulence in the gas. We focus here on turbulence generated by shocks, which is less dependent on the specifics of the merger. This paper is based on a more detailed work (Goldman 1997).

scholarly journals Clusters of Galaxies in a Flat CHDM Universe

1998 ◽  
Vol 188 ◽  
pp. 299-299
Author(s):  
A. Habe ◽  
C. Hanyu ◽  
S. Yachi
Keyword(s):  
Dark Matter ◽  
Large Scale ◽  
Large Scale Structure ◽  
Numerical Results ◽  
Clusters Of Galaxies ◽  
Statistical Features ◽  
X Ray ◽  
Numerical Resolution ◽  
Radiative Processes ◽  
The Universe

Cold and hot dark matter (CHDM) model is one of viable models which can reproduce the large scale structure of the universe. HDM may affect structure of clusters of galaxies in CHDM universe. Bryan et al. (1994) gave numerical results of CHDM model that explain some statistical features of X-ray clusters of galaxies, e.g. X-ray luminosiry-temperature realtion, L ∝~ T3.5, without considering radiative processes. However their numerical resolution is insufficient to resolve the cores of X-ray clusters. So, we simulate the formation of clusters in CHDM universe more carefully.

scholarly journals NEW RESULTS FROM H.E.S.S. OBSERVATIONS OF GALAXY CLUSTERS

2009 ◽  
Vol 18 (10) ◽  
pp. 1627-1631 ◽  
Author(s):  
◽  
WILFRIED DOMAINKO ◽  
DALIBOR NEDBAL ◽  
JAMES A. HINTON ◽  
OLIVIER MARTINEAU-HUYNH
Keyword(s):  
Cosmic Rays ◽  
Galaxy Clusters ◽  
Gamma Rays ◽  
Large Scale ◽  
Gamma Ray ◽  
Cosmic Ray ◽  
Clusters Of Galaxies ◽  
X Ray ◽  
Model Predictions ◽  
The Universe

Clusters of galaxies are believed to contain a significant population of cosmic rays. From the radio and probably hard X-ray bands it is known that clusters are the spatially most extended emitters of non-thermal radiation in the Universe. Due to their content of cosmic rays, galaxy clusters are also potential sources of VHE (> 100 GeV) gamma rays. Recently, the massive, nearby cluster Abell 85 has been observed with the H.E.S.S. experiment in VHE gamma rays with a very deep exposure as part of an ongoing campaign. No significant gamma-ray signal has been found at the position of the cluster. The non-detection of this object with H.E.S.S. constrains the total energy of cosmic rays in this system. For a hard spectral index of the cosmic rays of -2.1 and if the cosmic-ray energy density follows the large scale gas density profile, the limit on the fraction of energy in these non-thermal particles with respect to the total thermal energy of the intra-cluster medium is 8% for this particular cluster. This value is at the lower bounds of model predictions.

scholarly journals Dark Matter in Clusters of Galaxies

1995 ◽  
Vol 164 ◽  
pp. 227-235
Author(s):  
Claude R. Canizares
Keyword(s):  
Dark Matter ◽  
Galaxy Clusters ◽  
Gravitational Lensing ◽  
Clusters Of Galaxies ◽  
Rapid Progress ◽  
X Ray ◽  
Mass Distributions ◽  
The Past ◽  
Accurate Picture ◽  
Made In

An appropriate subtitle for this talk might be “Newton meets Einstein.” For many decades, the prime tool for studying the amount and distribution of matter in galaxy clusters was decidedly Newtonian, involving at first the measurements of the dynamics of the galaxies themselves and, for the past 15 years or so, the imputed dynamics of the hot, X-ray emitting intra-cluster gas. Einstein enters more recently with the introduction of gravitational lensing as a tool for studying cluster mass distributions. Rapid progress is being made in each of these areas, and there are now attempts to bring them together to give a consistent and more accurate picture of clusters.

scholarly journals Superclustering and Motion of Galaxy Clusters*

1988 ◽  
Vol 130 ◽  
pp. 229-238
Author(s):  
Neta A. Bahcall
Keyword(s):  
Dark Matter ◽  
Spatial Distribution ◽  
Shell Model ◽  
Galaxy Clusters ◽  
Large Scale ◽  
Clusters Of Galaxies ◽  
Large Scale Structures ◽  
Peculiar Velocities ◽  
Scale Structures ◽  
Shell Intersections

The evidence for the existence of very large scale structures, ∼ 100h−1 Mpc in size, as derived from the spatial distribution of clusters of galaxies is summarized. A “shell model” of galaxy clustering is described in which clusters of galaxies are located at shell intersections; the model yields results consistent with cluster observations. Detection of a ∼ 2000 km s−1 elongation in the redshift direction in the distribution of the clusters is also described. Possible causes of the effect are peculiar velocities of clusters on scales of 10–100h−1 Mpc and geometrical elongation of superclusters. If the effect is entirely due to the peculiar velocities of clusters, then superclusters have masses of order 1016,5M⊙ and may contain a larger amount of dark matter than previously anticipated.

scholarly journals On the relation between mini-halos and AGN feedback in clusters of galaxies

2020 ◽  
Vol 499 (2) ◽  
pp. 2934-2958
Author(s):  
A Richard-Laferrière ◽  
J Hlavacek-Larrondo ◽  
R S Nemmen ◽  
C L Rhea ◽  
G B Taylor ◽  
...  
Keyword(s):  
Large Scale ◽  
State Of The Art ◽  
Vital Role ◽  
Clusters Of Galaxies ◽  
Relativistic Jets ◽  
X Ray ◽  
Core Cluster ◽  
Central Galaxy ◽  
Central Regions ◽  
Radio Power

ABSTRACT A variety of large-scale diffuse radio structures have been identified in many clusters with the advent of new state-of-the-art facilities in radio astronomy. Among these diffuse radio structures, radio mini-halos are found in the central regions of cool core clusters. Their origin is still unknown and they are challenging to discover; less than 30 have been published to date. Based on new VLA observations, we confirmed the mini-halo in the massive strong cool core cluster PKS 0745−191 (z = 0.1028) and discovered one in the massive cool core cluster MACS J1447.4+0827 (z = 0.3755). Furthermore, using a detailed analysis of all known mini-halos, we explore the relation between mini-halos and active galactic nucleus (AGN) feedback processes from the central galaxy. We find evidence of strong, previously unknown correlations between mini-halo radio power and X-ray cavity power, and between mini-halo and the central galaxy radio power related to the relativistic jets when spectrally decomposing the AGN radio emission into a component for past outbursts and one for ongoing accretion. Overall, our study indicates that mini-halos are directly connected to the central AGN in clusters, following previous suppositions. We hypothesize that AGN feedback may be one of the dominant mechanisms giving rise to mini-halos by injecting energy into the intra-cluster medium and reaccelerating an old population of particles, while sloshing motion may drive the overall shape of mini-halos inside cold fronts. AGN feedback may therefore not only play a vital role in offsetting cooling in cool core clusters, but may also play a fundamental role in re-energizing non-thermal particles in clusters.

scholarly journals FORMATION OF DARK MATTER HALOES IN A HOMOGENEOUS DARK ENERGY UNIVERSE

2010 ◽  
Vol 19 (08n10) ◽  
pp. 1397-1403
Author(s):  
L. MARASSI
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Large Scale ◽  
State Parameter ◽  
Mass Function ◽  
Accelerated Expansion ◽  
X Ray ◽  
Energy Models ◽  
Dark Energy Component ◽  
Standard Press

Several independent cosmological tests have shown evidences that the energy density of the universe is dominated by a dark energy component, which causes the present accelerated expansion. The large scale structure formation can be used to probe dark energy models, and the mass function of dark matter haloes is one of the best statistical tools to perform this study. We present here a statistical analysis of mass functions of galaxies under a homogeneous dark energy model, proposed in the work of Percival (2005), using an observational flux-limited X-ray cluster survey, and CMB data from WMAP. We compare, in our analysis, the standard Press–Schechter (PS) approach (where a Gaussian distribution is used to describe the primordial density fluctuation field of the mass function), and the PL (power–law) mass function (where we apply a non-extensive q-statistical distribution to the primordial density field). We conclude that the PS mass function cannot explain at the same time the X-ray and the CMB data (even at 99% confidence level), and the PS best fit dark energy equation of state parameter is ω = -0.58, which is distant from the cosmological constant case. The PL mass function provides better fits to the HIFLUGCS X-ray galaxy data and the CMB data; we also note that the ω parameter is very sensible to modifications in the PL free parameter, q, suggesting that the PL mass function could be a powerful tool to constrain dark energy models.

scholarly journals Large-Scale Structure in the Universe: Spatial Distribution and Peculiar Velocities

1987 ◽  
Vol 124 ◽  
pp. 335-348
Author(s):  
Neta A. Bahcall
Keyword(s):  
Dark Matter ◽  
Spatial Distribution ◽  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Clusters Of Galaxies ◽  
Large Scale Structures ◽  
Peculiar Velocities ◽  
Scale Structures ◽  
The Universe

The evidence for the existence of very large scale structures, ∼ 100h−1Mpc in size, as derived from the spatial distribution of clusters of galaxies is summarized. Detection of a ∼ 2000 kms−1 elongation in the redshift direction in the distribution of the clusters is also described. Possible causes of the effect are peculiar velocities of clusters on scales of 10–100h−1Mpc and geometrical elongation of superclusters. If the effect is entirely due to the peculiar velocities of clusters, then superclusters have masses of order 1016.5M⊙ and may contain a larger amount of dark matter than previously anticipated.

scholarly journals X-ray Cluster Large Scale Structure and Cosmology

2005 ◽  
Vol 216 ◽  
pp. 373-380
Author(s):  
Marguerite Pierre
Keyword(s):  
Dark Energy ◽  
Galaxy Clusters ◽  
Large Scale ◽  
Scaling Law ◽  
Large Scale Structure ◽  
Short Review ◽  
Scale Structure ◽  
X Ray ◽  
Recent Advances

We outline the main arguments in favor of cosmological X-ray surveys of galaxy clusters. We summarize recent advances in our understanding of cluster physics. After a short review of past surveys, we present the scientific motivations of the XMM Large Scale Structure survey. We further illustrate how such a survey can help constrain the nature of the dark energy as well as cluster scaling law evolution, i.e. non-gravitational physics.

scholarly journals A deep learning view of the census of galaxy clusters in IllustrisTNG

2020 ◽  
Vol 498 (4) ◽  
pp. 5620-5628
Author(s):  
Y Su ◽  
Y Zhang ◽  
G Liang ◽  
J A ZuHone ◽  
D J Barnes ◽  
...  
Keyword(s):  
Deep Learning ◽  
Galaxy Clusters ◽  
Large Scale ◽  
Learning Algorithm ◽  
X Ray ◽  
Deep Learning Algorithm ◽  
Cluster Evolution ◽  
Novel Method ◽  
Massive Clusters ◽  
Activation Mapping

ABSTRACT The origin of the diverse population of galaxy clusters remains an unexplained aspect of large-scale structure formation and cluster evolution. We present a novel method of using X-ray images to identify cool core (CC), weak cool core (WCC), and non-cool core (NCC) clusters of galaxies that are defined by their central cooling times. We employ a convolutional neural network, ResNet-18, which is commonly used for image analysis, to classify clusters. We produce mock Chandra X-ray observations for a sample of 318 massive clusters drawn from the IllustrisTNG simulations. The network is trained and tested with low-resolution mock Chandra images covering a central 1 Mpc square for the clusters in our sample. Without any spectral information, the deep learning algorithm is able to identify CC, WCC, and NCC clusters, achieving balanced accuracies (BAcc) of 92 per cent, 81 per cent, and 83 per cent, respectively. The performance is superior to classification by conventional methods using central gas densities, with an average ${\rm BAcc}=81{{\ \rm per\ cent}}$, or surface brightness concentrations, giving ${\rm BAcc}=73{{\ \rm per\ cent}}$. We use class activation mapping to localize discriminative regions for the classification decision. From this analysis, we observe that the network has utilized regions from cluster centres out to r ≈ 300 kpc and r ≈ 500 kpc to identify CC and NCC clusters, respectively. It may have recognized features in the intracluster medium that are associated with AGN feedback and disruptive major mergers.

scholarly journals Magnetorotational instability in cool cores of galaxy clusters

2015 ◽  
Vol 81 (5) ◽  
Author(s):  
Carlo Nipoti ◽  
L. Posti ◽  
S. Ettori ◽  
M. Bianconi
Keyword(s):  
Heat Flux ◽  
Heat Conduction ◽  
Galaxy Clusters ◽  
Magnetized Plasma ◽  
Radiative Cooling ◽  
Clusters Of Galaxies ◽  
Magnetorotational Instability ◽  
X Ray ◽  
Stability Properties ◽  
Anisotropic Heat Conduction

Clusters of galaxies are embedded in halos of optically thin, gravitationally stratified, weakly magnetized plasma at the system’s virial temperature. Owing to radiative cooling and anisotropic heat conduction, such intracluster medium (ICM) is subject to local instabilities, which are combinations of the thermal, magnetothermal and heat-flux-driven buoyancy instabilities. If the ICM rotates significantly, its stability properties are substantially modified and, in particular, also the magnetorotational instability (MRI) can play an important role. We study simple models of rotating cool-core clusters and we demonstrate that the MRI can be the dominant instability over significant portions of the clusters, with possible implications for the dynamics and evolution of the cool cores. Our results give further motivation for measuring the rotation of the ICM with future X-ray missions such as ASTRO-H and ATHENA.

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