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.

Quantitative x-ray microfluorescence analysis of small areas and individual particles

1992 ◽  
Vol 50 (2) ◽  
pp. 1754-1755
Author(s):  
P. A. Pella ◽  
M. Lankosz ◽  
B. Holynska
Keyword(s):  
Gaussian Function ◽  
Normal Incidence ◽  
Video Camera ◽  
Rapid Progress ◽  
X Ray ◽  
Small Areas ◽  
The Past ◽  
Source Sample ◽  
Individual Particles ◽  
Made In

During the past few years, rapid progress has been made in the development of collimated x-ray sources which permit energy-dispersive x-ray analysis of small areas with dimensions below 100 μm. An x-ray microfluorescence spectrometer developed at NIST employs a commercial low-power (50 WATTS) x-ray tube providing a small focused x-ray beam (0.25 × 0.25 mm). The x-ray beam size was further reduced with a Mo collimator tipped with a Pt foil having a 70μm hole in the center. The x-ray beam profile was measured by step scanning across Cu wires 50 μm in diameter in both X and Y directions. The cross section of the beam was approximated by a Gaussian function with a FWHM of 43 μm. A schematic diagram of the spectrometer which is capable of operation in vacuum is shown in Figure 1.Other features include a close coupled source-sample-detector for optimum count rate, a motorized x-y stage, and a color video camera for continuous viewing of the sample at normal incidence.

scholarly journals Mapping Dark Matter Near Galaxy Clusters

1996 ◽  
Vol 173 ◽  
pp. 107-112
Author(s):  
J.A. Tyson
Keyword(s):  
Dark Matter ◽  
Galaxy Clusters ◽  
Gravitational Lensing ◽  
Total Mass ◽  
Surface Brightness ◽  
Rest Frame ◽  
Light Distribution ◽  
Clusters Of Galaxies ◽  
Direct Measure ◽  
V Band

Weak gravitational lensing can provide a direct measure of mass overdensity on scales of kpc to several Mpc. The total mass and light distribution in a survey of 32 clusters of galaxies is reviewed. The mass is derived from apodized inversion of thousands of weak lensing arclets in deep CCD shift-and-stare exposures to uniform faint surface brightness in two colors. Rest frame V band mass-to-light ratios of several hundred h solar are found.

scholarly journals Constraining the inner density slope of massive galaxy clusters

2020 ◽  
Vol 496 (4) ◽  
pp. 4717-4733 ◽  
Author(s):  
Qiuhan He ◽  
Hongyu Li ◽  
Ran Li ◽  
Carlos S Frenk ◽  
Matthieu Schaller ◽  
...  
Keyword(s):  
Dark Matter ◽  
Galaxy Clusters ◽  
Gravitational Lensing ◽  
Matter Density ◽  
Stellar Kinematics ◽  
Density Profiles ◽  
Mass Distributions ◽  
Dark Matter Density ◽  
Dark Matter Mass ◽  
Massive Galaxy

ABSTRACT We determine the inner density profiles of massive galaxy clusters (M200 > 5 × 1014 M⊙) in the Cluster-EAGLE (C-EAGLE) hydrodynamic simulations, and investigate whether the dark matter density profiles can be correctly estimated from a combination of mock stellar kinematical and gravitational lensing data. From fitting mock stellar kinematics and lensing data generated from the simulations, we find that the inner density slopes of both the total and the dark matter mass distributions can be inferred reasonably well. We compare the density slopes of C-EAGLE clusters with those derived by Newman et al. for seven massive galaxy clusters in the local Universe. We find that the asymptotic best-fitting inner slopes of ‘generalized’ Navarro–Frenk–White (gNFW) profiles, γgNFW, of the dark matter haloes of the C-EAGLE clusters are significantly steeper than those inferred by Newman et al. However, the mean mass-weighted dark matter density slopes of the simulated clusters are in good agreement with the Newman et al. estimates. We also find that the estimate of γgNFW is very sensitive to the constraints from weak lensing measurements in the outer parts of the cluster and a bias can lead to an underestimate of γgNFW.

scholarly journals Observable tests of self-interacting dark matter in galaxy clusters: cosmological simulations with SIDM and baryons

2019 ◽  
Vol 488 (3) ◽  
pp. 3646-3662 ◽  
Author(s):  
Andrew Robertson ◽  
David Harvey ◽  
Richard Massey ◽  
Vincent Eke ◽  
Ian G McCarthy ◽  
...  
Keyword(s):  
Dark Matter ◽  
Galaxy Clusters ◽  
Gravitational Lensing ◽  
Interaction Strength ◽  
Matter Distribution ◽  
Cosmological Simulations ◽  
X Ray ◽  
Critical Curves ◽  
Strong Lensing ◽  
Dark Matter Distribution

ABSTRACT We present bahamas-SIDM, the first large-volume, $(400 \, h^{-1} \mathrm{\, Mpc})^{3}$, cosmological simulations including both self-interacting dark matter (SIDM) and baryonic physics. These simulations are important for two primary reasons: (1) they include the effects of baryons on the dark matter distribution and (2) the baryon particles can be used to make mock observables that can be compared directly with observations. As is well known, SIDM haloes are systematically less dense in their centres, and rounder, than CDM haloes. Here, we find that that these changes are not reflected in the distribution of gas or stars within galaxy clusters, or in their X-ray luminosities. However, gravitational lensing observables can discriminate between DM models, and we present a menu of tests that future surveys could use to measure the SIDM interaction strength. We ray-trace our simulated galaxy clusters to produce strong lensing maps. Including baryons boosts the lensing strength of clusters that produce no critical curves in SIDM-only simulations. Comparing the Einstein radii of our simulated clusters with those observed in the CLASH survey, we find that at velocities around $1000 \mathrm{\, km \, s^{-1}}$ an SIDM cross-section of $\sigma /m \gtrsim 1 \, \mathrm{cm^2 \, g^{-1}}$ is likely incompatible with observed cluster lensing.

scholarly journals Two Analytic Relations Connecting the Hot Gas Astrophysics with the Cold Dark Matter Model for Galaxy Clusters

2021 ◽  
Vol 923 (1) ◽  
pp. 95
Author(s):  
Man Ho Chan
Keyword(s):  
Dark Matter ◽  
Galaxy Clusters ◽  
Gravitational Lensing ◽  
Cold Dark Matter ◽  
X Ray ◽  
Hot Gas ◽  
Cold Dark Matter Model ◽  
Matter Model ◽  
Analytical Relations ◽  
Dark Matter Model

Abstract Galaxy clusters are good targets for examining our understanding of cosmology. Apart from numerical simulations and gravitational lensing, X-ray observation is the most common and conventional way to analyze the gravitational structures of galaxy clusters. Therefore, it is valuable to have simple analytical relations that can connect the observed distribution of the hot, X-ray-emitting gas to the structure of the dark matter in the clusters as derived from simulations. In this article, we apply a simple framework that can analytically connect the hot gas empirical parameters with the standard parameters in the cosmological cold dark matter model. We have theoretically derived two important analytic relations, r s ≈ 3 r c and ρ s ≈ 9 β kT / 8 π Gm g r c 2 , which can easily relate the dark matter properties in galaxy clusters with the hot gas properties. This can give a consistent picture describing gravitational astrophysics for galaxy clusters by the hot gas and cold dark matter models.

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 Gravitational Lensing — Models

1986 ◽  
Vol 119 ◽  
pp. 529-538 ◽  
Author(s):  
Ramesh Narayan
Keyword(s):  
Dark Matter ◽  
Gravitational Lensing ◽  
General Model ◽  
Mass Distributions ◽  
The Past ◽  
Elliptical Model ◽  
Model Independent ◽  
Fermat’S Principle ◽  
Fermat's Principle

Qualitative features of gravitational lensing are discussed in terms of a scalar framework based on Fermat's principle. The lensing action of galaxy-like models with spherical and elliptical mass distributions are described. The elliptical model has three distinct regimes of lensing, of which two correspond to lensing with three images and one with five images. One of the three-image geometries has been frequently explored in the past. Models proposed for 0957+561 correspond to this. The five-image geometry has been invoked for 1115+080. Some general model-independent properties of gravitational lensing are listed. If image parities were available, it might be possible to make statements about the lensing mass even when it is made up of dark matter.

scholarly journals DYNAMICS OF CLUSTERS OF GALAXIES WITH EXTENDED F(chi) GRAVITY

2019 ◽  
Vol 55 (2) ◽  
pp. 237-254
Author(s):  
Tula Bernal ◽  
Oliver López-Corona ◽  
Sergio Mendoza
Keyword(s):  
Dark Matter ◽  
Fourth Order ◽  
Gravitational Lensing ◽  
Relativistic Correction ◽  
Clusters Of Galaxies ◽  
Order Of Approximation ◽  
X Ray ◽  
Flat Rotation Curves ◽  
Theory Of Gravity ◽  
Dynamical Masses

In this article, we present the results of a fourth order perturbation analysis of the metric theory of gravity f(chi) = chi^(3/2) , with chi a suitable dimensionless Ricci scalar. Such a model corresponds to a specific f(R) metric theory of gravity, where the mass of the system is included in the gravitational field's action. In previous works we have shown that, up to the second order in perturbations, this theory reproduces the flat rotation curves of galaxies and the details of the gravitational lensing in individual, groups, and clusters of galaxies. Here, leaving fixed the results from our previous works, we show that the theory reproduces the dynamical masses of 12 Chandra X-ray galaxy clusters, without the need of dark matter, through the metric coefficients up to the fourth order of approximation. In this sense, we calculate the first relativistic correction of the f(chi) metric theory and apply it to fit the dynamical masses of clusters of galaxies.

scholarly journals Dark Matter or Additional Gravitational Forces Generated by Non-Spherical Mass Distributions?

2017 ◽  
Vol 01 (02) ◽  
pp. 1750004
Author(s):  
Enbang Li
Keyword(s):  
Dark Matter ◽  
Galaxy Clusters ◽  
Gravitational Lensing ◽  
Modern Science ◽  
Theory Of Relativity ◽  
Distribution Models ◽  
Mass Distributions ◽  
Negative Results ◽  
Spherical Mass ◽  
The Masses

The measured orbital velocity distributions of stars in galaxies and the observed gravitational lensing effects in galaxy clusters suggest that there should be more mass than that can be explained by the visible mass of stars, gas and dust in the galaxies. This unseen mass or matter, generally referred to as dark matter, has puzzled physicists for a few decades and has now become one of the greatest unsolved mysteries in modern science. So far, all of the efforts aiming to generate and detect the exotic dark matter substance have yielded negative results. Here, starting from Newton’s law of gravity, we show that the spherical mass distribution models originally employed for estimating the masses of galaxies could cause the discrepancy between the actual masses and those calculated from the rotational velocities. It is demonstrated that additional gravitational effects are generated from non-spherical mass distributions in the cosmic structures. The currently observed rotation curves and gravitational lensing effects in galaxies and galaxy clusters could be explained under the frameworks of Newtonian gravity and Einstein’s general theory of relativity when proper mass distributions are considered.

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