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-Cluster 4, with a fraction of the particles projected onto the x − z plane. Note the filamentary structure, with clumps beading up in the filaments. The dashed circle marks the sphere of radius R sphere to within which we have restricted our analysis (see text).
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Hierarchical theories of structure formation predict that clusters of galaxies should be embedded in a web like structure, with filaments emanating from them to large distances. The amount of mass contained within such filaments near a cluster can be comparable to the collapsed mass of the cluster itself. Diffuse infalling material also contains a...
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... of the clusters we examined was surrounded by a large amount of mass. Most of this material appeared by eye to be collapsed into "beads" along a filamentary struc- ture, although a small number of clumps could be found outside the filaments. We show a projection of a fraction of the points from the simulation of cluster 4 in Fig. 1. The filamentary structure and satellites are easily evident. Note that this filamentary structure extends well beyond our radius R sphere . No single projection can show the full 3D nature of the structure, in which the filamentarity is even more apparent. Since much of this mass is at low density it is unlikely it would be a site for ...
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Citations
... Galaxy clusters can be detected based on a number of different properties, such as X-ray emission from hot intracluster gas (e.g., Sarazin 1988;Reichardt et al. 2013), the Sunyaev-Zeldovich (SZ) effect (Planck Collaboration et al. 2011), optical (e.g., Abell et al. 1989;den Hartog & Katgert 1996;Abdullah et al. 2011) and infrared emissions (e.g., Genzel & Cesarsky 2000;Muzzin et al. 2009;Wilson et al. 2009;Wylezalek et al. 2014) from stars in cluster members, Stellar Bump Sequence (Muzzin et al. 2013), and the gravitational lensing (e.g., Metzler et al. 1999;Kubo et al. 2009). Using current capabilities, both X-ray emission and SZ effect are detectable only for the very deep gravitational potential wells of the most massive systems. ...
Utilizing the SDSS-DR13 spectroscopic data set, we create a new publicly available catalog of 1800 galaxy clusters (GalWeight cluster catalog, GalWCat19 ) and a corresponding catalog of 34,471 identified member galaxies. The clusters are identified from overdensities in redshift phase space. The GalWeight technique introduced by Abdullah et al. is then applied to identify cluster members. The completeness of the cluster catalog ( GalWCat19 ) and the procedure followed to determine cluster mass are tested on the Bolshoi N -body simulations. The 1800 GalWCat19 clusters range in redshift between 0.01 and 0.2 and have masses in the range of (0.4–14) × 10 ¹⁴ h ⁻¹ M ⊙ . The cluster catalog provides a large number of cluster parameters, including sky position, redshift, membership, velocity dispersion, and mass at overdensities Δ = 500, 200, 100, and 5.5. The 34,471 member galaxies are identified within the radius at which the density is 200 times the critical density of the universe. The galaxy catalog provides the coordinates of each galaxy and the ID of the cluster that the galaxy belongs to. The cluster velocity dispersion scales with mass as = + (0.349 ± 0.142) , with a scatter of δ log σ = 0.06 ± 0.04. The catalogs are publicly available at https://mohamed-elhashash-94.webself.net/galwcat/ .
... Galaxy clusters can be detected based on a number of different properties, such as X-ray emission from hot in-tracluster gas (e.g., Sarazin 1988;Reichardt et al. 2013), the Sunyaev-Zeldovich (SZ) effect (Planck Collaboration et al. 2011), optical (e.g., Abell et al. 1989;den Hartog & Katgert 1996;Abdullah et al. 2011) and infrared emissions (e.g., Genzel & Cesarsky 2000;Muzzin et al. 2009;Wilson et al. 2009;Wylezalek et al. 2014) from stars in cluster members, Stellar Bump Sequence (Muzzin et al. 2013), and the gravitational lensing (e.g., Metzler et al. 1999;Kubo et al. 2009). Using current capabilities, both X-ray emission and SZ effect are detectable only for the very deep gravitational potential wells of the most massive systems. ...
Utilizing the SDSS-DR13 spectroscopic dataset, we create a new publicly-available catalog of 1,870 galaxy clusters (GalWeight cluster catalog, $\mathtt{GalWCat19}$) and a corresponding catalog of 38,536 identified member galaxies. The clusters are identified from overdensities in redshift-phase space. The GalWeight technique introduced in Abdullah, Wilson and Klypin (AWK18) is then applied to identify cluster members. The completeness of the cluster catalog ($\mathtt{GalWCat19}$) and the procedure followed to determine cluster mass are tested on the Bolshoi N-body simulations. The 1,870 $\mathtt{GalWCat19}$ clusters range in redshift between $0.01 - 0.2$ and in mass between $(0.4 - 14) \times 10^{14}h^{-1}M_{\odot}$. The cluster catalog provides a large number of cluster parameters including sky position, redshift, membership, velocity dispersion, and mass at overdensities $\Delta = 500, 200, 100, 5.5$. The 38,536 member galaxies are identified within the radius at which the density is 200 times the critical density of the Universe. The galaxy catalog provides the coordinates of each galaxy and the ID of the cluster that the galaxy belongs to. The cluster velocity dispersion scales with mass as $\log(\sigma_{200})=\log(933\pm29~ \mbox{km} ~ \mbox{s}^{-1}) +(0.35\pm0.04)\log\left[h(z) ~ M_{200}/10^{15}M_\odot\right]$ with scatter of $\delta = 0.06$. The fundamental dynamical parameters of the cluster sample do not show evolution in the redshift interval $0.0 < z < 0.2$. The catalogs are publicly available at the following website\footnote{\url{https://mohamed-elhashash-94.webself.net/}}.
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Die vorliegende Arbeit beschäftigt sich mit Galaxienhaufen. Diese massereichsten, gravitativ gebundenen Objekte im beobachtbaren Universum repräsentieren das obere Ende der Massenfunktion und sind von speziellem Interesse für die Kosmologie. Nicht nur lassen sich mehrere kosmologische Parameter aus der Beobachtung und vor allem aus der Massenbestimmung von Galaxienhaufen ableiten, sie stellen auch ideale kosmische Laboratorien dar, welche einen direkten Vergleich zwischen Beobachtung und numerischer Simulation erlauben. Die vielleicht vielversprechendste Methode um die Eigenschaften von Galaxienhaufen zu ermitteln ist der Gravitationslinseneffekt. Das Licht entfernter Hintergrundgalaxien wird aufgrund der hohen Massekonzentration in einem Galaxienhaufen auf dem Weg zum Beobachter abgelenkt und trägt daher Informationen über den Deflektor. In dieser Arbeit entwickeln wir eine neue, moderne Methode welche den sogenannten starken und schwachen Gravitationslinseneffekt optimal kombiniert und daher eine nichtparametrische Rekonstruktion der Massenverteilung des Deflektors erlaubt. Diese Methode ist in einem fortschrittlichen numerischen Algorithmus implementiert, welcher effiziente numerische Verfahren und parallele Höchstleistungs-Computersysteme ausnutzt. Mit Rekonstruktionen numerisch simulierter Galaxienhaufen zeigen wir die Leistungsfähigkeit unserer Methode, im Vergleich mit etablierten Techniken. Wir schließen unsere Arbeit mit Rekonstruktion und Analyse von MS2137.3-2353 und CL0024+1654, zweier wohlbekannter Galaxienhaufen die spektakuläre Phänomene des starken Gravitationslinseneffektes aufweisen.
Galactic rotation curve is a powerful indicator of the state of the gravitational field within a galaxy. The flatness of these curves indicates the presence of dark matter (DM) in galaxies and their clusters. In this paper, we focus on the possibility of explaining the rotation curves of spiral galaxies without postulating the existence of DM in the framework of [Formula: see text] gravity, where the gravitational Lagrangian is written by an arbitrary function of [Formula: see text], the Ricci scalar and of [Formula: see text], the trace of energy–momentum tensor [Formula: see text]. We derive the gravitational field equations in this gravity theory for the static spherically symmetric spacetime and solve the equations for metric coefficients using a specific model that has minimal coupling between matter and geometry. The orbital motion of a massive test particle moving in a stable circular orbit is considered and the behavior of its tangential velocity with the help of the considered model is studied. We compare the theoretical result predicted by the model with observations of a sample of 19 galaxies by generating and fitting rotation curves for the test particle to check the viability of the model. It is observed that the model could almost successfully explain the galactic dynamics of these galaxies without the need of DM at large distances from the galactic center.
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We present the results of an X-ray follow-up campaign targeting 10 weak-lensing (WL)-selected galaxy clusters from a Subaru WL survey. Archival Chandra data exist for two of the clusters, and we obtain dedicated observations of the remaining eight. The WL clusters appear to
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host a cool core, consistent with Sunyaev–Zel'dovich-effect-selected clusters. This fraction is much lower than observed in
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This review is based on the paper of Kneib & Natarajan (2011). I
briefly review the strong lensing methods and presents the main results
Strong Lensing studies achieved in recent years in the domain of
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Here we present the weak-lensing results for A1758, which is known to consist of four subclusters undergoing two separate mergers, A1758N and A1758S. Weak-lensing results for A1758N agree with previous weak-lensing results for clusters 1E0657-558 (Bullet cluster) and MACS J0025.4-1222, whose X-ray gas components were found to be largely separated from their clusters' gravitational potentials. A1758N has a geometry that is different from previously published mergers in that one of its X-ray peaks overlays the corresponding gravitational potential and the other X-ray peak is well separated from its cluster's gravitational potential. The weak-lensing mass peaks of the two northern clusters are separated at the 2.5σ level. We estimate the combined mass of the clusters in A1758N to be (2.2 ± 0.5) × 1015M
☉ and r
200 = 2300+100– 130 kpc. We also detect seven strong-lensing candidates, two of which may provide information that would improve the mass measurements of A1758N.
We describe a new approach to constraining the amplitude of the power spectrum of matter perturbations in the universe, parameterized by σ8 as a function of the matter density Ω0. We compare the galaxy cluster X-ray luminosity function of the ROSAT-ESO Flux-Limited X-Ray (REFLEX) survey with the theoretical mass function of Jenkins et al., using the mass-luminosity relationship obtained from weak lensing data for a sample of galaxy clusters identified in Sloan Digital Sky Survey commissioning data and confirmed through cross-correlation with the ROSAT All-Sky Survey. We find σ8 = 0.38Ω, which is significantly different from most previous results derived from comparable calculations that used the X-ray temperature function. We discuss possible sources of systematic error that may cause such a discrepancy and in the process uncover a possible inconsistency between the REFLEX luminosity function and the relation between cluster X-ray luminosity and mass obtained by Reiprich & Böhringer.
