Tracing the non-thermal pressure and hydrostatic bias in galaxy clusters

Ettori, S.; Eckert, D.

doi:10.1051/0004-6361/202142638

Cited by 17 publications

(7 citation statements)

References 28 publications

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“…Overall, we can see that the hydrostatic mass bias does not significantly affect the estimated sparsity, with a bias of the order of few per cent and in most cases compatible with a vanishing bias with only a few exceptions. This is consistent with the results of the recent analysis based on observed X-ray clusters presented in Ettori & Eckert ( 2022 ), which yield sparsity biasses at the per cent level and consistent with having no bias at all. Ho we v er, we hav e seen in the case of the WL mass bias that even though the effect on the measured sparsity remains small, the scatter around the true sparsity can severely affect the efficiency of the detector at identifying recent mergers.…”

Section: Hydrostatic Mass Biassupporting

confidence: 92%

“…Deviations from this condition can induce a radially dependent bias on the cluster masses (see e.g. Biffi et al 2016 ;Eckert et al 2019 ;Ettori & Eckert 2022 ), thus affecting the estimation of the cluster's sparsity. The hydrostatic mass bias has been studied in Biffi et al ( 2016 ), who have realized cosmological zoom N -body/hydro simulations of 29 clusters to e v aluate the bias of masses at o v erdensities = 200, 500, and 2500 (in units of the critical density) for Cool Core (CC) and No Cool Core (NCC) clusters, as defined with respect to the entropy in the core of their sample, as well as for regular and disturbed clusters defined by the offset of the centre of mass and the fraction of substructures.…”

Section: Hydrostatic Mass Biasmentioning

confidence: 99%

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Timing the last major merger of galaxy clusters with large halo sparsity

Richardson

Corasaniti

2022

Monthly Notices of the Royal Astronomical Society

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Numerical simulations have shown that massive dark matter haloes, which today host galaxy clusters, assemble their mass over time alternating periods of quiescent accretion and phases of rapid growth associated with major merger episodes. Observations of such events in clusters can provide insights on the astrophysical processes that characterise the properties of the intra-cluster medium, as well as the gravitational processes that contribute to their assembly. It is therefore of prime interest to devise a fast and reliable way of detecting such perturbed systems. We present a novel approach to identifying and timing major mergers in clusters characterised by large values of halo sparsity. Using halo catalogues from the MultiDark-Planck2 simulation, we show that major merger events disrupt the radial mass distribution of haloes, thus leaving a distinct universal imprint on the evolution of halo sparsity over a period not exceeding two dynamical times. We exploit this feature using numerically calibrated distributions to test whether an observed galaxy cluster with given sparsity measurements has undergone a recent major merger and to eventually estimate when such an event occurred. We implement these statistical tools in a specifically developed public python library lammas, which we apply to the analysis of Abell 383 and Abell 2345 as test cases. Finding that, for example, Abell 2345 had a major merger about 2.1 ± 0.2 Gyr ago. This work opens the way to detecting and timing major mergers in galaxy clusters solely through measurements of their mass at different radii.

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Section: Hydrostatic Mass Biassupporting

confidence: 92%

Section: Hydrostatic Mass Biasmentioning

confidence: 99%

Timing the last major merger of galaxy clusters with large halo sparsity

Richardson

Corasaniti

2022

Monthly Notices of the Royal Astronomical Society

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“…[41] classify this cluster as dynamically active based on the central entropy estimates. However, the X-COP clusters are on average relaxed systems due to the selection applied [41], and this has been confirmed from the observed hydrostatic bias and the negligible amount of non-thermal pressure support [44] (see also [46], which reaffirmed the earlier conclusions using a new method to estimate the hydrostatic bias and non-thermal pressure).…”

Section: Recap Of Resultssupporting

confidence: 71%

A test of galaxy cluster fundamental plane for the X-COP sample

Pradyumna¹,

Desai²

2022

J. Cosmol. Astropart. Phys.

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We test the galaxy cluster fundamental plane using the X-COP sample of 12 clusters. The fundamental plane is given by the relation TX ∝ Ms α rs β, where TX, Ms, and rs correspond to the gas temperature, NFW halo mass, and scale radius, respectively. We did this analysis using two different temperatures: the error-weighted temperature in (50–500)h-1 kpc as well as the mass-weighted temperature in the same range. With both these temperatures, we find a very tight fundamental plane with dispersion of about 0.02 dex. The best-fit values for α and β are in-between those expected from virial equilibrium and self-similarity solution for secondary infall and collapse, with α being closer to the virial expectation. Our best-fit values are also consistent with a recent re-analyses of the fundamental plane for the CLASH sample, after excluding the hottest clusters.

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“…Therefore, several studies investigated the impact of modifications to the way the mass observable relations are determined on the cluster abundance observable with relative success when trying to account for it as solution to the σ 8 discrepancy. One line targeted the cooling and heating processes closely related to cluster mass determination, such as the work by McDonald et al (2017), Henson et al (2017), and Mummery et al (2017), who showed, using hydrodynamic simulations, that using a different mass weighted cooling scheme or taking into account non-thermal pressure coming from bulk and turbulent motions of gas in the intracluster medium (Shi et al 2016;Ettori & Eckert 2022) could reduce the hydrostatic bias, although still below the amount needed to reconcile the observed cluster number count with CMB. Another study was performed by the second release of the Planck collaboration (Planck Collaboration et al 2016a) on the impact of the signal-to-noise ratio (S/N) on the number of detections, but found that it would be necessary for Planck to have missed nearly 40% of the clusters with predicted SZ S/N > 7 in order for the SZ and CMB cluster number count to match with a level of scatter with cluster structure inconsistent with the predictions of current hydrodynamical simulations.…”

Section: Introductionmentioning

confidence: 99%

Cluster counts

Sakr

Ilić

Blanchard

2022

A&A

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Despite the success of the Lambda cold dark matter (ΛCDM) cosmological model, current estimations of the amplitude of matter fluctuations (σ 8 ) show an appreciable difference between its value inferred from the cosmic microwave background (CMB) angular power spectrum (C ℓ ) and those obtained from cluster counts. Neutrinos or a modification of the growth of structures had been previously investigated as the possible origin of this discrepancy. In this work we examine whether further extensions to the ΛCDM model could alleviate the tension. To this end, we derived constraints on the parameters subject to the discrepancy, using CMB C ℓ combined with cluster counts from the Sunyaev-Zel'dovich (SZ) sample with a free dark energy equation of state parameter, while allowing the cluster mass calibration parameter (1−b) to vary. This latter is degenerate with σ 8 , which translates the discrepancy within the ΛCDM framework into one between (1−b) ∼ 0.6, corresponding to constraints on σ 8 obtained from CMB, and (1−b) ∼ 0.8, the value adopted for the SZ sample calibration. We find that a constant w, when left free to vary along with large priors on the matter density ([0.1,1.0]) and the Hubble parameters ([30,200]), can reduce the discrepancy to less than 2σ for values far below its fiducial w = -1. However, such low values of w are not allowed when we add other probes like the baryonic acoustic oscillation (BAO) feature angular diameter distance measured in galaxy clustering surveys. We also found, when we allow to vary in addition to w a modification of the growth rate through the growth index γ, that the tension is alleviated, with the (1 − b) likelihood now centred around the Planck calibration value of ∼ 0.8. However, here again, combining CMB and cluster counts with geometrical distance probes restores the discrepancy, with the (1 − b) preferred value reverting back to the ΛCDM value of ∼ 0.6. The same situation is observed when introducing, along with w and γ, further extensions to ΛCDM (e.g. massive neutrinos), although these extensions reduce the tension to 2σ, even when combined with BAO datasets. We also explore other common extensions by comparing two cases: allowing a dynamical w following a CPL parametrisation in addition to a constant growth index, and when the growth index is expanded through a second parameter γ 1 along with a constant w. In the former we reach the same conclusions as with the case of a constant w and γ, where the discrepancy was alleviated only if we do not constrain w by BAO, while in the latter case, we observe that introducing γ 1 drives (1 − b) towards lower values that would instead increase the discrepancy on σ 8 . We conclude that none of these common extensions to ΛCDM is able to fix the discrepancy and a misdetermination of the calibration factor is the most preferred explanation. Finally, we investigate the effect on our posteriors from limiting the Hubble constant priors to the usual common adopted range of [30,100].

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Tracing the non-thermal pressure and hydrostatic bias in galaxy clusters

Cited by 17 publications

References 28 publications

Timing the last major merger of galaxy clusters with large halo sparsity

Timing the last major merger of galaxy clusters with large halo sparsity

A test of galaxy cluster fundamental plane for the X-COP sample

Cluster counts

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