Density Profiles Of Galaxy Clusters Research Articles

Correction to: X-ray surface brightness and gas density profiles of galaxy clusters up to 3 × R500c with SRG/eROSITA

Correction to: X-ray surface brightness and gas density profiles of galaxy clusters up to 3 × <i>R</i>500c with SRG/eROSITA

X-ray surface brightness and gas density profiles of galaxy clusters up to 3 × R500c with SRG/eROSITA

ABSTRACT Using the data of the SRG/eROSITA all-sky survey, we stacked a sample of ∼40 galaxy cluster images in the 0.3–2.3 keV band, covering the radial range up to 10 × R500c. The excess emission on top of the Galactic and extragalactic X-ray backgrounds and foregrounds is detected up to ∼3 × R500c. At these distances, the surface brightness of the stacked image drops below ∼1 per cent of the background. The density profile reconstructed from the X-ray surface brightness profile agrees well (within ∼30 per cent) with the mean gas profile found in numerical simulations, which predict the local gas overdensity of ∼ 20–30 at 3 × R500c and the gas fraction close to the universal value of $\frac{\Omega _b}{\Omega _m}\approx 0.15$ in the standard Λ cold dark matter model. Taking at face value, this agreement suggests that up to ∼3 × R500c the X-ray signal is not strongly boosted by the gas clumpiness, although a scenario with a moderately inhomogeneous gas cannot be excluded. A comparison of the derived gas density profile with the electron pressure profile based on the Sunyaev-Zeldovich (SZ) effect measurements suggests that by r ∼ 3 × R500c the gas temperature drops by a factor of ∼ 4–5 below the characteristic temperature of a typical cluster in the sample within R500c, while the entropy keeps growing up to this distance. Better constraints on the gas properties just beyond 3 × R500c should be possible with a sample larger than used for this pilot study.

Super interacting dark sector: An improvement on self-interacting dark matter via scaling relations of galaxy clusters

Self-interacting dark matter is known as one of the most appropriate candidates for dark matter. Due to its excellent success in removing many astrophysical problems, particularly in small scale structure, studying this model has taken on added significance. In this paper, we focus on the results of two previously performed simulations of cluster sized halos with self-interacting dark matter and introduce a new function for the density profile of galaxy clusters, which can perfectly describe the result of these simulations. This density profile helps to find a velocity dispersion profile and also a relation between cluster mass and concentration parameter. Using these relations, we investigate two scaling relations of galaxy clusters, namely mass-velocity dispersion and mass-temperature relations. The scaling relations reveal that in the self-interacting dark matter model, halos are more massive than what the standard non-interacting model predicts for any fixed temperature. We also study the mass-temperature relation for a hybrid interacting model, which is a combination of self-interacting dark matter idea with another model of the dark sector in which dark matter particle mass is determined according to its interaction with dark energy. This super interacting dark sector (SIDS) model can change the mass-temperature relation to a modified form that has the same result as a non-interacting model. Finally, we provide quantitative expressions which can describe the constants of this interacting model with the value of cross-section per unit mass of dark matter particles.

The Three Hundred Project: The evolution of galaxy cluster density profiles

Recent numerical studies of the dark matter density profiles of massive galaxy clusters ($M_{\rm halo} > 10^{15}$M$_{\odot}$) show that their median radial mass density profile remains unchanged up to $z > 1$, displaying a highly self-similar evolution. We verify this by using the data set of the THE THREE HUNDRED project, i.e. 324 cluster-sized haloes as found in full physics hydrodynamical simulations. We track the progenitors of the mass-complete sample of clusters at $z=0$, and find that their median shape is already in place by $z=2.5$. However, selecting a dynamically relaxed subsample ($\sim16$ per cent of the clusters), we observe a shift of the scale radius $r_s$ towards larger values at earlier times. Classifying the whole sample by formation time, this evolution is understood as a result of a two-phase halo mass accretion process. Early-forming clusters -- identified as relaxed today -- have already entered their slow accretion phase, hence their mass growth occurs mostly at the outskirts. Late-forming clusters -- which are still unrelaxed today -- are in their fast accretion phase, thus the central region of the clusters is still growing. We conclude that the density profile of galaxy clusters shows a profound self-similarity out to redshifts $z\sim2.5$. This result holds for both gas and total density profiles when including baryonic physics, as reported here for two rather distinct sub-grid models.

The diverse density profiles of galaxy clusters with self-interacting dark matter plus baryons

Abstract We present the first simulated galaxy clusters (M200 &amp;gt; 1014 M⊙) with both self-interacting dark matter (SIDM) and baryonic physics. They exhibit a greater diversity in both dark matter and stellar density profiles than their counterparts in simulations with collisionless dark matter (CDM), which is generated by the complex interplay between dark matter self-interactions and baryonic physics. Despite variations in formation history, we demonstrate that analytical Jeans modelling predicts the SIDM density profiles remarkably well, and the diverse properties of the haloes can be understood in terms of their different final baryon distributions.

The Halo Boundary of Galaxy Clusters in the SDSS

Abstract Analytical models and simulations predict a rapid decline in the halo density profile associated with the transition from the “infalling” regime outside the halo to the “collapsed” regime within the halo. Using data from SDSS, we explore evidence for such a feature in the density profiles of galaxy clusters using several different approaches. We first estimate the steepening of the outer galaxy density profile around clusters, finding evidence for truncation of the halo profile. Next, we measure the galaxy density profile around clusters using two sets of galaxies selected on color. We find evidence of an abrupt change in galaxy colors that coincides with the location of the steepening of the density profile. Since galaxies that have completed orbits within the cluster are more likely to be quenched of star formation and thus appear redder, this abrupt change in galaxy color can be associated with the transition from single-stream to multi-stream regimes. We also use a standard model comparison approach to measure evidence for a “splashback”-like feature, but find that this approach is very sensitive to modeling assumptions. Finally, we perform measurements using an independent cluster catalog to test for potential systematic errors associated with cluster selection. We identify several avenues for future work: improved understanding of the small-scale galaxy profile, lensing measurements, identification of proxies for the halo accretion rate, and other tests. With upcoming data from the DES, KiDS, and HSC surveys, we can expect significant improvements in the study of halo boundaries.

Testing the gas mass density profile of galaxy clusters with distance duality relation

In this paper, assuming the validity of distance duality relation, $\eta=D_L(z)(1+z)^{-2}/D_A(z)=1$, where $D_A(z)$ and $D_L(z)$ are the angular and the luminosity distance respectively, we explore two kinds of gas mass density profiles of clusters: the isothermal $\beta$ model and the non-isothermal double-$\beta$ model. In our analysis, performed on 38 massive galaxy clusters observed by \textit{Chandra} (within the redshift range of $0.14<z<0.89$), we use two types of cluster gas mass fraction data corresponding to different mass density profiles fitted to the X-ray data. Using two general parameterizations of $\eta(z)$ (phenomenologically allowing for distance duality violation), we find that the non-isothermal double-$\beta$ model agrees better with the distance duality relation, while the isothermal $\beta$ model tends to be marginally incompatible with the Etherington theorem at 68.3% CL. However, current accuracy of the data does not allow to distinguish between the two models for the gas-density distribution at a significant level.

Combining weak and strong cluster lensing: applications to simulations and MS 2137

AIMS. While weak lensing cannot resolve cluster cores and strong lensing is almost insensitive to density profiles outside the scale radius, combinations of both effects promise to constrain density profiles of galaxy clusters well, and thus to allow testing of the CDM expectation on dark-matter halo density profiles. METHODS. We develop an algorithm further that we had recently proposed for this purpose. It recovers a lensing potential optimally reproducing observations of both strong and weak-lensing effects by combining high resolution in cluster cores with the larger-scale information from weak lensing. The main extensions concern the accommodation of mild non-linearity in inner iterations, the progressive increase in resolution in outer iterations, and the introduction of a suitable regularisation term. The linearity of the method is essentially preserved. RESULTS. We demonstrate the success of the algorithm with both idealised and realistic simulated data, showing that the simulated lensing mass distribution and its density profile are well reproduced. We then apply it to weak and strong lensing data of the cluster MS 2137 and obtain a parameter-free solution which is in good qualitative agreement with earlier parametric studies.

The effects of ellipticity and substructure on estimates of cluster density profiles based on lensing and kinematics

We address the question of how well the density profile of galaxy clusters can be determined by combining strong lensing and velocity dispersion data. We use cosmological dark matter simulations of clusters to test the reliability of the method, producing mock catalogues of tangential and radial gravitational arcs and simulating the radial velocity dispersion profile of the cluster brightest central galaxy. The density profiles of the simulated clusters closely follow the NFW form, but we find that the recovered values of the inner slope are systematically underestimated, by about 0.4 in the mean, if the lens is assumed to be axially symmetric. However, if the ellipticity and orientation of the iso-contours of the cluster lensing potential are taken into account, then the inner slopes can be recovered quite accurately for a significant subset of the clusters whose central surface density profiles appear the most regular. These have lensing potentials with ellipticities in the range 0.15-0.4. Further simulations projecting one cluster along many random lines-of-sight show that, even for lower ellipticities, the central slopes are underestimated by $\sim 10-35%$. These simulations closely mimic past observations (see e.g. Sand et al., 2004), suggesting that existing estimates of the central slopes may be biased towards low values. For the remaining clusters, where the lensing potential is strongly perturbed by active merging or by substructure, the correct determination of the inner slope requires a more accurate model for the lens. When the halo profile is modelled by a generalised NFW profile, we find that the inferred scale radius and characteristic density, unlike the inner slope, are generally poorly constrained, since there is a strong degeneracy between these two parameters.

Cluster masses from CMB and galaxy weak lensing

Gravitational lensing can be used to directly constrain the projected density profile of galaxy clusters. We discuss possible future constraints using lensing of the cosmic microwave background (CMB) temperature and polarization, and compare to results from using galaxy weak lensing. We model the moving lens and kinetic Sunyaev-Zel'dovich signals that confuse the temperature CMB lensing when cluster velocities and angular momenta are unknown, and show how they degrade parameter constraints. The CMB polarization cluster lensing signal is {approx}1 {mu}K for massive clusters and challenging to detect; however it should be significantly cleaner than the temperature signal and may provide the most robust constraints at low noise levels. Galaxy lensing is likely to be much better for constraining cluster masses at low redshift, but for clusters at redshift z > or approx. 1 future CMB lensing observations may be able to do better.

XMM‐NewtonObservations of Evolution of Cluster X‐Ray Scaling Relations atz = 0.4–0.7

We present a spatially-resolved analysis of the temperature and gas density profiles of galaxy clusters at z=0.4-0.7 observed with XMM-Newton. These data are used to derive the total cluster mass within the radius r_500 without assuming isothermality, and also to measure the average temperature and total X-ray luminosity excluding the cooling cores. We derive the high-redshift M-T and L-T relations and compare them with the local measurements. The high-redshift L-T relation has low scatter and evolves as L ~ (1+z)^{1.8\pm0.3} for a fixed T, in good agreement with several previous Chandra and XMM-Newton studies (Vikhlinin et al., Lumb et al., Maughan et al.). The observed evolution of the M-T relation follows M_500 = A T^{3/2} E(z)^{-alpha}, where we measure alpha=0.88\pm0.23. This is in good agreement with predictions of the self-similar theory, alpha=1.

Radial Arc Statistics: A Powerful New Probe of the Central Density Profile of Galaxy Clusters

We show that the number ratio of radial arcs to tangential arcs in a cluster of galaxies depends sensitively on the central density profile of galaxy clusters but depends little on the lensing parameter and the threshold ellipticity of the lensed images. Based on these results, we propose a method to constrain the central density profile of clusters using radial arc statistics. A tentative comparison with the observations shows that radial arc statistics can be a powerful tool for constraining the cluster central density profile. Our results show that a systematic survey of radial and tangential arcs for an unbiased uniform cluster sample can be a promising test of the fundamental characteristics of dark matter.