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Hans Publishers, Astronomy & Astrophysics, (578), p. A46

DOI: 10.1051/0004-6361/201425470

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

Journal article published in 2015 by S. Ettori, A. Baldi, I. Balestra ORCID, F. Gastaldello, S. Molendi, P. Tozzi
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Red circle
Preprint: archiving forbidden
Red circle
Postprint: archiving forbidden
Red circle
Published version: archiving forbidden
Data provided by SHERPA/RoMEO

Abstract

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 3 bins (0-0.15, 0.15-0.4, >0.4) R500, as obtained with similar analysis using XMM-Newton data in Leccardi & Molendi (2008) and Baldi et al. (2012). 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. The average, redshift-independent, metal abundance measured in the 3 radial bins decrease moving outwards, with a mean metallicity in the core that is even 3 (two) times higher than the value of 0.16 times the solar abundance in Anders & Grevesse (1989) estimated at r>0.4 R500 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 given radius. A significant scatter, intrinsic to the observed distribution and of the order of 0.05-0.15, is observed below 0.4 R500. The nominal best-fit value of $γ$ is significantly different from zero in the inner cluster regions ($γ = 1.6 ± 0.2$) and in CC clusters only. These results are confirmed also with a bootstrap analysis, which provides a still significant negative evolution in the core of CC systems (P>99.9 per cent). No redshift-evolution is observed when regions above the core (r > 0.15 R500) are considered. A reasonable good fit of both the radial and redshift dependence is provided from the functional form $Z(r,z)=Z_0 (1+(r/0.15 R500)^2)^{-β} (1+z)^{-γ}$, 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. Our results represent the most extensive study of the spatially-resolved metal distribution in the cluster plasma as function of redshift. ; Comment: 5 pages. Research Note accepted for publication in A&A