Volume 592, August 2016
|Number of page(s)||18|
|Section||Cosmology (including clusters of galaxies)|
|Published online||24 August 2016|
Origin of central abundances in the hot intra-cluster medium
I. Individual and average abundance ratios from XMM-Newton EPIC
1 SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
2 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
3 Institute of Astronomy, Madingley Road, CB3 0 HA Cambridge, UK
4 Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany
5 Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, 452 Lomita Mall, Stanford, CA 94305, USA
6 Department of Physics, Stanford University, 382 Via Pueblo Mall, Stanford, CA 94305-4060, USA
Received: 24 November 2015
Accepted: 3 June 2016
The hot intra-cluster medium (ICM) is rich in metals, which are synthesised by supernovae (SNe) explosions and accumulate over time into the deep gravitational potential well of clusters of galaxies. Since most of the elements visible in X-rays are formed by type Ia (SNIa) and/or core-collapse (SNcc) supernovae, measuring their abundances gives us direct information on the nucleosynthesis products of billions of SNe since the epoch of the star formation peak (z ~ 2−3). In this study, we use the EPIC and RGS instruments on board XMM-Newton to measure the abundances of nine elements (O, Ne, Mg, Si, S, Ar, Ca, Fe, and Ni) from a sample of 44 nearby cool-core galaxy clusters, groups, and elliptical galaxies. We find that the Fe abundance shows a large scatter (~20−40%) over the sample, within 0.2r500 and especially 0.05r500. Unlike the absolute Fe abundance, the abundance ratios (X/Fe) are uniform over the considered temperature range (~0.6−8 keV) and with a limited scatter. In addition to an unprecedented treatment of systematic uncertainties, we provide the most accurate abundance ratios measured so far in the ICM, including Cr/Fe and Mn/Fe which we firmly detected (>4σ with MOS and pn independently). We find that Cr/Fe, Mn/Fe, and Ni/Fe differ significantly from the proto-solar values. However, the large uncertainties in the proto-solar abundances prevent us from making a robust comparison between the local and the intra-cluster chemical enrichments. We also note that, interestingly, and despite the large net exposure time (~4.5 Ms) of our dataset, no line emission feature is seen around ~3.5 keV.
Key words: X-rays: galaxies: clusters / galaxies: clusters: general / galaxies: clusters: intracluster medium / galaxies: abundances / supernovae: general / dark matter
© ESO, 2016
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