Constraining the origin and models of chemical enrichment in galaxy clusters using the Athena X-IFU

F Mernier,P Peille,M Gaspari,L Tornatore,E Pointecouteau,F Pajot,S Ettori,J Wilms,T Dauser,K Dolag,D Barret,S Borgani,E Cucchetti,E Rasia,N Clerc,E Bulbul,V Biffi,M Roncarelli

doi:10.1051/0004-6361/202038638

Abstract

Chemical enrichment of the Universe at all scales is related to stellar winds and explosive supernovae phenomena. Metals produced by stars and later spread throughout the intracluster medium (ICM) at the megaparsec scale become a fossil record of the chemical enrichment of the Universe and of the dynamical and feedback mechanisms determining their circulation. As demonstrated by the results of the soft X-ray spectrometer onboard Hitomi, high-resolution X-ray spectroscopy is the path to differentiating among the models that consider different metal-production mechanisms, predict the outcoming yields, and are a function of the nature, mass, and/or initial metallicity of their stellar progenitor. Transformational results shall be achieved through improvements in the energy resolution and effective area of X-ray observatories, allowing them to detect rarer metals (e.g. Na, Al) and constrain yet-uncertain abundances (e.g. C, Ne, Ca, Ni). The X-ray Integral Field Unit (X-IFU) instrument onboard the next-generation European X-ray observatory Athena is expected to deliver such breakthroughs. Starting from 100 ks of synthetic observations of 12 abundance ratios in the ICM of four simulated clusters, we demonstrate that the X-IFU will be capable of recovering the input chemical enrichment models at both low (z = 0.1) and high (z = 1) redshifts, while statistically excluding more than 99.5% of all the other tested combinations of models. By fixing the enrichment models which provide the best fit to the simulated data, we also show that the X-IFU will constrain the slope of the stellar initial mass function within ∼12%. These constraints will be key ingredients in our understanding of the chemical enrichment of the Universe and its evolution.

Highlights

The processes that lead to chemical enrichment of the Universe remain one of the major open questions in astrophysics
Starting from 100 ks of synthetic observations of 12 abundance ratios in the intracluster medium (ICM) of four simulated clusters, we demonstrate that the X-ray Integral Field Unit (X-IFU) will be capable of recovering the input chemical enrichment models at both low (z = 0.1) and high (z = 1) redshifts, while statistically excluding more than 99.5% of all the other tested combinations of models
By fixing the enrichment models which provide the best fit to the simulated data, we show that the X-IFU will constrain the slope of the stellar initial mass function within ∼12%

Summary

Introduction

The processes that lead to chemical enrichment of the Universe remain one of the major open questions in astrophysics. Most of the light elements (H, He, Li) were produced in the very first minutes of the Universe, during the primordial nucleosynthesis (Cyburt et al 2016). Are instead more recent, as most of this enrichment is related to supernovae events (SNe) and to stellar winds (Burbidge et al 1957). Elements from O to Si are predominantly produced by fusion reactions in the outer shells of massive stars (M ≥ 10 M ) during core-collapse supernovae (SNcc, see Nomoto et al 2013 for a review), while heavier elements (i.e. Si to Fe) are mostly related to thermonuclear explosions of white dwarfs (WDs) – former remnants of low-mass stars

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