The Mass Profile of Galaxy Clusters out to ∼2r200

We discuss the possibility that the cold dark matter mass profiles contain information on the cosmological constant [Formula: see text], and that such information constrains the nature of cold dark matter (CDM). We call this approach Modified Dark Matter (MDM). In particular, we examine the ability of MDM to explain the observed mass profiles of 13 galaxy clusters. Using general arguments from gravitational thermodynamics, we provide a theoretical justification for our MDM mass profile. In order to properly fit the shape of the mass profiles in galaxy clusters, we find it necessary to generalize the MDM mass profile from the one we used previously to fit galactic rotation curves. We successfully compare it to the NFW mass profiles both on cluster and galactic scales, though differences in form appear with the change in scales. Our results suggest that indeed the CDM mass profiles contain information about the cosmological constant in a nontrivial way.

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The history of metal enrichment traced by X-ray observations of high redshift galaxy clusters

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab2430 ◽

2021 ◽

Author(s):

Anthony M Flores ◽

Adam B Mantz ◽

Steven W Allen ◽

R Glenn Morris ◽

Rebecca E A Canning ◽

...

Keyword(s):

Galaxy Clusters ◽

High Redshift ◽

Substantial Improvement ◽

Metal Enrichment ◽

X Ray ◽

Redshift Galaxy ◽

History Of ◽

Mass Profile ◽

Massive Clusters ◽

Massive Galaxy

Abstract We present the analysis of deep X-ray observations of 10 massive galaxy clusters at redshifts 1.05 < z < 1.71, with the primary goal of measuring the metallicity of the intracluster medium (ICM) at intermediate radii, to better constrain models of the metal enrichment of the intergalactic medium. The targets were selected from X-ray and Sunyaev-Zel’dovich (SZ) effect surveys, and observed with both the XMM-Newton and Chandra satellites. For each cluster, a precise gas mass profile was extracted, from which the value of r500 could be estimated. This allows us to define consistent radial ranges over which the metallicity measurements can be compared. In general, the data are of sufficient quality to extract meaningful metallicity measurements in two radial bins, r < 0.3r500 and 0.3 < r/r500 < 1.0. For the outer bin, the combined measurement for all ten clusters, Z/Z⊙ = 0.21 ± 0.09, represents a substantial improvement in precision over previous results. This measurement is consistent with, but slightly lower than, the average metallicity of 0.315 Solar measured at intermediate-to-large radii in low-redshift clusters. Combining our new high-redshift data with the previous low-redshift results allows us to place the tightest constraints to date on models of the evolution of cluster metallicity at intermediate radii. Adopting a power law model of the form Z∝(1 + z)γ, we measure a slope $\gamma = -0.5^{+0.4}_{-0.3}$, consistent with the majority of the enrichment of the ICM having occurred at very early times and before massive clusters formed, but leaving open the possibility that some additional enrichment in these regions may have occurred since a redshift of 2.

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JoXSZ: Joint X-SZ fitting code for galaxy clusters

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037543 ◽

2020 ◽

Vol 639 ◽

pp. A73 ◽

Cited By ~ 1

Author(s):

Fabio Castagna ◽

Stefano Andreon

Keyword(s):

Galaxy Clusters ◽

Missing Values ◽

High Redshift ◽

Background Level ◽

X Ray ◽

Calibration Uncertainty ◽

User Request ◽

Mass Profile ◽

X Ray Background ◽

Fully Bayesian

The thermal Sunyaev-Zeldovich (SZ) effect and the X-ray emission offer separate and highly complementary probes of the thermodynamics of the intracluster medium. We present JoXSZ, the first publicly available code designed to jointly fit SZ and X-ray data coming from various instruments to derive the thermodynamic profiles of galaxy clusters. JoXSZ follows a fully Bayesian forward-modelling approach, accounts for the SZ calibration uncertainty, and for the X-ray background level systematic. It improves upon most current and not publicly available analyses because it adopts the correct Poisson-Gauss expression for the joint likelihood, makes full use of the information contained in the observations, even in the case of missing values within the datasets, has a more inclusive error budget, and adopts a consistent temperature in the various parts of the code, allowing for differences between X-ray and SZ gas-mass weighted temperatures when required by the user. JoXSZ accounts for beam smearing and data analysis transfer function, accounts for the temperature and metallicity dependencies of the SZ and X-ray conversion factors, adopts flexible parametrisation for the thermodynamic profiles, and on user request, allows either adopting or relaxing the assumption of hydrostatic equilibrium (HE). When HE holds, JoXSZ uses a physical (positive) prior on the radial derivative of the enclosed mass and derives the mass profile and overdensity radii rΔ. For these reasons, JoXSZ goes beyond simple SZ and electron density fits. We illustrate the use of JoXSZ by combining Chandra and NIKA data of the high-redshift cluster CL J1226.9+3332. The code is written in Python, it is fully documented, and the users are free to customise their analysis in accordance with their needs and requirements. JoXSZ is publicly available on GitHub.

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Matter Distribution in the Galaxy Clusters A 539 and A 2319

Symposium - International Astronomical Union ◽

10.1017/s0074180900115396 ◽

1998 ◽

Vol 188 ◽

pp. 329-329

Author(s):

D. Trèvese ◽

G. Cirimele ◽

M. de Simone

Keyword(s):

Temperature Gradient ◽

Galaxy Clusters ◽

Radial Distribution ◽

Hydrostatic Equilibrium ◽

Gas Temperature ◽

Matter Distribution ◽

The Public ◽

The Galaxy ◽

Mass Profile ◽

New Evidence

We performed a combined X-ray and optical analysis of the two clusters A539 and A2319, based on ROSAT PSPC 0.4-2.4 keV images of the public archive and F band photometry from microdensitometric scans of Palomar 48 inch plates (Trèvese et al. 1992, A&AS, 94, 327). Assuming spherical symmetry and following the methods adopted in Cirimele, Nesci, and Trèvese (1997, ApJ, 475, 11 (CNT97)) we derived the radial distribution of gas and galaxy densities ρgas and ρgal and we have computed the morphological parameter βxo ≡ d ln ρgas(r)/d ln ρgal(r), introduced in CNT97. This allows to check the validity of the hydrostatic equilibrium condition, which reads, for an isotropic and uniform velocity distribution of r.m.s. dispersion σr. In the case of A539, adopting σr=629 km s−1 from Fadda et al. (1996, ApJ, 473, 670) and T=1.57 keV David et al. (1996, ApJ, 473, 692), we obtained marginally consistent values of βspec= 1.54±0.50 and βxo=1.08±0.11. In the case of A2319 we took into account the presence of the secondary component A2319B (Oegerle et al. 1995, AJ, 110, 32) and the temperature gradient (Markevitch M. 1996, ApJ, 465, L1). The resulting radial increase of βspec is consistent with that of (βxo(r) + d ln T(r)/d ln ρgal), suggesting that the hydrostatic equilibrium holds also in the presence of a temperature gradient. The radial distribution of the total binding mass, the mass in galaxies and intergalactic gas show that in both clusters the gas mass profile is steeper than galaxies and total masses consistently with our previous results (CNT97). Adopting a constant gas temperature, the relevant baryon fractions are larger than 20 %, adding new evidence to the “baryon catastrophe”. Taking into account the radial decrease of gas temperature, the baryon fraction is further increased. This implies that either Ωo < 0.25, or that large halos of dark matter surround galaxy clusters, as suggested by White & Fabian (1995, MNRAS, 273, 72).

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Using the Outskirts of Galaxy Clusters to Determine their Mass Accretion Rate

10.20944/preprints201612.0057.v1 ◽

2016 ◽

Author(s):

Cristiano De Boni

Keyword(s):

Dark Matter ◽

Spherical Shell ◽

Galaxy Clusters ◽

Accretion Rate ◽

Redshift Range ◽

Mass Accretion Rate ◽

The Mean ◽

Mass Profile

We explore the possibility of using the external regions of galaxy clusters to measure their mass accretion rate (MAR). The main goal is to provide a method to observationally investigate the growth of structures on the nonlinear scales of galaxy clusters. We derive the MAR by using the mass profile beyond the splashback radius, evaluating the mass of a spherical shell and the time it takes to fall in. The infall velocity of the shell is extracted from N-body simulations. The average MAR returned by our prescription in the redshift range z=[0, 2] is within 20-40% of the average MAR derived from the merger trees of dark matter haloes in the reference N-body simulations. Our result suggests that the external regions of galaxy clusters can be used to measure the mean MAR of a sample of clusters.

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