Structure and scaling of the entropy in nearby galaxy clusters

Pratt, G. W.; Arnaud, M.; Pointecouteau, É.

doi:10.1051/0004-6361:20054025

Cited by 93 publications

(182 citation statements)

References 42 publications

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“…Comparing to previous work, a wide variety of slopes have been found from fits to the entropy-temperature relation at 0.1 R 200 , ranging from very shallow (α = 0.49 ± 0.15: Pratt et al 2006; α = 0.50 ± 0.08: Nagai et al 2007) to very steep (α = 0.92 ± 0.12: Sanderson et al 2009; α = 0.85 ± 0.19: this work). We simply note that cool core-only samples tend to yield shallower slopes than statistically-selected samples, a fact borne out in the present data, for which the entropy temperature relation at 0.1 R 200 for the cool core subsample has a slope of α = 0.63 ± 0.94, while the morphologically disturbed subsample has a slope of α = 1.22 ± 0.76.…”

Section: Entropy Scaling Relationssupporting

confidence: 57%

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Gas entropy in a representative sample of nearby X-ray galaxy clusters (REXCESS): relationship to gas mass fraction

Pratt

Arnaud²,

Piffaretti³

et al. 2010

A&A

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309

415

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We examine the radial entropy distribution and its scaling using 31 nearby galaxy clusters from the representative XMM-Newton cluster structure survey (REXCESS), a sample in the temperature range 2−9 keV selected in X-ray luminosity only, with no bias toward any particular morphological type. The entropy profiles are robustly measured at least out to R 1000 in all systems and out to R 500 in thirteen systems. Compared to theoretical expectations from non-radiative cosmological simulations, the observed distributions show a radial and mass-dependent excess entropy, such that the excess is greater and extends to larger radii in lower mass systems. At R 500 , the mass dependence and entropy excess are both negligible within the large observational and theoretical uncertainties. Mirroring this behaviour, the scaling of gas entropy is shallower than self-similar in the inner regions, but steepens with radius, becoming consistent with self-similar at R 500 . There is a large dispersion in scaled entropy in the inner regions, apparently linked to the presence of cool cores and dynamical activity; at larger radii the dispersion decreases by approximately a factor of two to 30 per cent, and the dichotomy between subsamples disappears. There are two peaks in the distribution of both inner slope and, after parameterising the profiles with a power law plus constant model, in central entropy K 0 . However, we are unable to distinguish between a bimodal or a left-skewed distribution of K 0 with the present data. The distribution of outer slopes is unimodal with a median value of 0.98, and there is a clear correlation of outer slope with temperature. Renormalising the dimensionless entropy profiles by the gas mass fraction profile f gas (

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Section: Entropy Scaling Relationssupporting

confidence: 57%

“…Simulated profiles flatten in the very central regions due to entropy mixing (Wadsley et al 2008;Mitchell et al 2009). Observed profiles are also found generally to have similar external slopes (e.g., Pratt et al 2006;Sun et al 2009) and to flatten in the central regions in high Fig. 3.…”

Section: Radial Entropy Structurementioning

confidence: 67%

Gas entropy in a representative sample of nearby X-ray galaxy clusters (REXCESS): relationship to gas mass fraction

Pratt

Arnaud²,

Piffaretti³

et al. 2010

A&A

Self Cite

309

415

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show abstract

“…Markevitch et al 1998;Arnaud & Evrard 1999;Mohr & Evrard 1997;Finoguenov et al 2001;Ikebe et al 2002;Ponman et al 2003;Ettori et al 2004;Vikhlinin et al 2005;Pointecouteau et al 2005;Arnaud et al 2005;Pratt et al 2006;Kotov & Vikhlinin 2006;Zhang et al 2006;Maughan et al 2006;Maughan 2007;Arnaud et al 2007;Pratt et al 2009;Mantz et al 2010;Arnaud et al 2010;Sun et al 2011;Reichert et al 2011). An investigation of the relevant literature shows, however, that a number different methods are used for scaling the data at different redshifts.…”

Section: Introductionmentioning

confidence: 99%

Modelling self-similar appearance of galaxy clusters in X-rays

Böhringer

Dolag

Chon

2012

A&A

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Context. The largest uncertainty for cosmological studies using clusters of galaxies is introduced by our limited knowledge of the statistics of galaxy cluster structure and the related scaling relations between observables and cluster mass. A large effort has therefore been made to compile global galaxy cluster properties, in particular those obtained through X-ray observations, and to study their scaling relations. However, the scaling schemes used in the literature differ. Aims. The present paper aims to clarify this situation by providing a thorough review of the scaling laws within the standard model of large-scale structure growth and to discuss various steps in practical approximations. Methods. We derived the scaling laws for X-ray observables and cluster mass within the pure gravitational structure growth scenario. Using N-body simulations we tested the recent formation approximation used in earlier analytic approaches. It involves a redshiftdependent overdensity parameter. We find this approximation less precise than using a fiducial radius based on a fixed overdensity with respect to critical density. Results. Inspired by the comparison of the predicted scaling relations with observations, we propose a first-order modification of the scaling scheme to include the observed effects of hydrodynamics in structure formation. This modification involves a cluster-mass dependent gas-mass fraction. We also discuss the observational results of the reshift evolution of the most important scaling relations and find that a redshift dependence of the gas mass to total mass relation also has to be invoked within our modification scheme. Conclusions. We find that the current observational data are, within their uncertainties, consistent with the proposed modified scaling laws.

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“…Young et al 2011, and references therein). For example, star formation (galaxy feedback) is a suspected source of non-gravitational entropy excess (Buote et al 2007;Pratt et al 2006;Sun et al 2009), yet the amount of star formation required to reproduce the observed X-ray derived quantities (e.g. baryon fraction in gas or mass-temperature scaling relations) is at least ten times greater than the amount of stars observed (Gonzalez et al 2007;Kravtsov et al 2009;Andreon 2010).…”

Section: Introductionmentioning

confidence: 99%

The enrichment history of the intracluster medium: a Bayesian approach

Andreon

2012

A&A

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This work measures the evolution of the iron content in galaxy clusters by a rigorous analysis of the data of 130 clusters at 0.1 < z < 1.3. This task is made difficult by a) the low signal-to-noise ratio of abundance measurements and the upper limits; b) possible selection effects; c) boundaries in the parameter space; d) non-Gaussian errors; e) the intrinsic variety of the objects studied; and f) abundance systematics. We introduce a Bayesian model to address all these issues at the same time, thus allowing cross-talk (covariance). On simulated data, the Bayesian fit recovers the input enrichment history, unlike in standard analysis. After accounting for a possible dependence on X-ray temperature, for metal abundance systematics, and for the intrinsic variety of studied objects, we found that the present-day metal content is not reached either at high or at low redshifts, but gradually over time: iron abundance increases by a factor 1.5 in the 7 Gyr sampled by the data. Therefore, feedback in metal abundance does not end at high redshift. Evolution is established with a moderate amount of evidence, 19 to 1 odds against faster or slower metal enrichment histories. We quantify, for the first time, the intrinsic spread in metal abundance, 18 ± 3%, after correcting for the effect of evolution, X-ray temperature, and metal abundance systematics. Finally, we also present an analytic approximation of the X-ray temperature and metal abundance likelihood functions, which are useful for other regression fitting involving these parameters. The data for the 130 clusters and code used for the stochastic computation are provided with the paper.

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Structure and scaling of the entropy in nearby galaxy clusters

Cited by 93 publications

References 42 publications

Gas entropy in a representative sample of nearby X-ray galaxy clusters (REXCESS): relationship to gas mass fraction

Gas entropy in a representative sample of nearby X-ray galaxy clusters (REXCESS): relationship to gas mass fraction

Modelling self-similar appearance of galaxy clusters in X-rays

The enrichment history of the intracluster medium: a Bayesian approach

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