An<i>XMM-Newton</i>spatially-resolved study of metal abundance evolution in distant galaxy clusters

Baldi, A.; Ettori, S.; Molendi, S.; Balestra, I.; Gastaldello, F.; Tozzi, P.

doi:10.1051/0004-6361/201117836

Cited by 53 publications

(78 citation statements)

References 39 publications

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“…Thus, we had to degrade the spatial resolution of Leccardi & Molendi (2008) abundance profiles to match its resolution with Baldi et al (2012a) and obtain uniform abundance profiles in three radial bins: 0−0.15 R 500 , 0.15−0.4 R 500 , and >0.4 R 500 , where R 500 is estimated through a scaling relation (e.g. Vikhlinin et al 2006;see Baldi et al 2012 for details) by using a global gas temperature that does not include the core emission (<0.15 R 500 ).…”

Section: Discussionmentioning

confidence: 99%

“…In a consistent and similar way (see details in Leccardi & Molendi 2008;Baldi et al 2012a), we resolved the cluster emission for all objects in the data set in three different regions: the core region (corresponding to 0 < r < 0.15 R 500 ), the region immediately surrounding the core (0.15 R 500 < r < 0.4 R 500 ), and the outskirts of the cluster (r > 0.4 R 500 ). Using the pseudo-entropy ratio σ, we also distinguish between cool core and non-cool core objects, with CC clusters that represent ∼35 per cent of the whole sample.…”

Section: Discussionmentioning

confidence: 99%

“…Balestra et al 2007;Maughan et al 2008;Anderson et al 2009; a statistical analysis of the combination of these different data sets is presented in Andreon 2012). In Baldi et al (2012a), we have presented Article published by EDP Sciences A46, page 1 of 5 the XMM-Newton analysis of 39 galaxy clusters at 0.4 < z < 1.4, covering a temperature range of 2 < ∼ kT < ∼ 12.8 keV. We were able to resolve their abundance in three radial bins.…”

Section: Introductionmentioning

confidence: 99%

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The evolution of the spatially resolved metal abundance in galaxy clusters up toz= 1.4

Ettori

Baldi

Balestra

et al. 2015

A&A

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Context. We present the combined analysis of the metal content of 83 objects in the redshift range 0.09−1.39, and spatially resolved in the three bins (0−0.15, 0.15−0.4, >0.4) R 500 , as obtained with similar analysis using XMM-Newton data in our previous two papers. Aims. By combining these two large data sets, we investigate the relations between abundance, temperature, radial position and redshift holding in the intracluster medium. Methods. We fit functional forms to the combination of the different physical quantities of interest, i.e., intracluster medium (ICM) metal abundance, radius, and redshift. We use the pseudo-entropy ratio to separate the cool core (CC) cluster population, where the central gas density tends to be relatively higher, cooler and more metal rich, from the non-cool core systems. Results. The average, redshift-independent, metal abundance measured in the three radial bins decreases moving outwards, with a mean metallicity in the core that is even three (two) times higher than the value of 0.16 times the solar abundance in Anders & Grevesse (1989, Geochim. Cosmochim. Acta, 53, 197) estimated at r > 0.4 R 500 in CC (NCC) objects. We find that the values of the emission-weighted metallicity are well fitted by the relation Z(z) = Z 0 (1 + z) −γ at the given radius. A significant scatter, intrinsic to the observed distribution and of the order of 0.05−0.15, is observed below 0.4 R 500 . The nominal best-fit value of γ is significantly different from zero (>3σ) in the inner cluster regions (γ = 1.6 ± 0.2) and in CC clusters only. These results are also confirmed with a bootstrap analysis, which provides a still significant negative evolution in the core of CC systems (P > 99.9 per cent, when counting the number of random repetitions, which yields γ > 0). No redshift evolution is observed when regions above the core (r > 0.15 R 500 ) are considered. A reasonable good fit of both the radial and redshift dependence is provided from the functional form Z(r, z) = Z 0 (1 + (r/0.15 R 500 ) 2 ) −β (1 + z) −γ , with (Z 0 , β, γ) = (0.83 ± 0.13, 0.55 ± 0.07, 1.7 ± 0.6) in CC clusters and (0.39 ± 0.04, 0.37 ± 0.15, 0.5 ± 0.5) for NCC systems. Conclusions. Our results represent the most extensive study of the spatially resolved metal distribution in the cluster plasma as function of redshift. Our study defines the limits that numerical and analytic models describing the metal enrichment in the ICM have to meet.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The evolution of the spatially resolved metal abundance in galaxy clusters up toz= 1.4

Ettori

Baldi

Balestra

et al. 2015

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“…Furthermore, unless individual spectra all have the same S/N, the best-fit metal abundance will be biased toward the metal abundance of the spectrum with the highest S/N. Finally, if an intrinsic scatter is not allowed, a redshift trend may be overly driven by a single high S/N measurement, as noted by Baldi et al (2011), who note the dramatic effect of including, or removing, a very low upper limit in a fit where the intrinsic scatter is not allowed.…”

Section: Intrinsic Scattermentioning

confidence: 99%

The enrichment history of the intracluster medium: a Bayesian approach

Andreon

2012

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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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“…Also, contrary to some initial findings 6,7 , there should be no substantial redshift evolution in the ICM metallicity outside of the central regions of clusters, out to z ~ 2. The presence and strength of such evolution are a matter of ongoing debate 2,23,24 . The observed large iron abundance of the high-entropy gas in the outskirts of the Perseus Cluster is also consistent with the idea that the highest-energy cosmic rays (above a few 10 18 eV) may be primarily iron nuclei 25 accelerated by cluster formation shocks 26 .…”

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A uniform metal distribution in the intergalactic medium of the Perseus cluster of galaxies

Werner

Urban

Simionescu

et al. 2013

Nature

143

133

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Most of the metals (elements heavier than helium) ever produced by stars in the member galaxies of galaxy clusters currently reside within the hot, X-ray emitting intra-cluster gas. Observations of X-ray line emission from this intergalactic medium have suggested a relatively small cluster-to-cluster scatter outside of the cluster centers 1,2 and enrichment with iron out to large radii 3,4,5 , leading to the idea that the metal enrichment occurred early in the history of the Universe 3 . Models with early enrichment predict a uniform metal distribution at large radii in clusters, while late-time enrichment, favored by some previous studies 6,7 , is expected to introduce significant spatial variations of the metallicity. To discriminate clearly between these competing models, it is essential to test for potential inhomogeneities by measuring the abundances out to large radii along multiple directions in clusters, which has not hitherto been done. Here we report a remarkably uniform measured iron abundance, as a function of radius and azimuth, that is statistically consistent with a constant value of ZFe = 0.306 ± 0.012 Solar out to the edge of the nearby Perseus Cluster. This homogeneous distribution requires that most of the metal enrichment of the intergalactic medium occurred before the cluster formed, likely over 10 billion years ago, during the period of maximal star formation and black hole activity.Between 2009 and 2011, we obtained a total of 84 observations of the Perseus Cluster with the Suzaku X-ray satellite, as a Key Project for that mission. The pointings covered eight azimuthal directions from the cluster center out to an offset angle of 2 o , with a total exposure time of over 1 million seconds. We have analyzed the data from all three functioning X-ray Imaging Spectrometers, extracting spectra from annuli centered on the cluster center. We modeled the spectra from each of the 76 independent regions as a single-temperature thermal plasma in collisional ionization equilibrium, with the temperature, iron abundance, and spectrum normalization included as free parameters 8 .The measured radial and azimuthal variation of the iron abundance of the hot intra-cluster medium (ICM) out to the edge of the Perseus Cluster along the eight different directions is presented in Fig. 1. We define this `edge' as r200, the radius within which the mean enclosed mass density of the cluster is 200 times the critical density of the Universe at the cluster redshift (for the Perseus Cluster r200 = 1.8 Mpc, corresponding to 82 arcmin 4 ). We have tested the statistical uniformity of the measured iron abundance at radii r > 400 kpc (i.e. beyond the central metallicity peak associated with the brightest cluster galaxy 4,9 ) by modeling the data from all radii and azimuths with a constant abundance. The measured chi-square value of 65.8 for 75 degrees of freedom is consistent with the null hypothesis of a constant iron abundance with a value of ZFe = 0.306±0.012 Solar (68% confidence limit; we adopt a Solar iron abundance of ...

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AnXMM-Newtonspatially-resolved study of metal abundance evolution in distant galaxy clusters

Cited by 53 publications

References 39 publications

The evolution of the spatially resolved metal abundance in galaxy clusters up toz= 1.4

The evolution of the spatially resolved metal abundance in galaxy clusters up toz= 1.4

The enrichment history of the intracluster medium: a Bayesian approach

A uniform metal distribution in the intergalactic medium of the Perseus cluster of galaxies

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