Chemical enrichment in the Ophiuchus cluster core studied by high-resolution XRISM spectroscopy

Abstract Galaxy clusters provide an ideal laboratory for investigating the chemical enrichment history of the universe because they host the hot intracluster medium (ICM), which contains various chemical elements. The X-ray observations have constituted a unique way to measure the element abundance and composition of the ICM due to their prominent emission lines in the 0.1–10 keV range. We explore the metal abundances and chemical enrichment in the cool-core galaxy cluster, Ophiuchus, by using a 217 ks XRISM data set. The abundances of Si, S, Ar, Ca, Cr, Mn, Fe, and Ni are accurately determined using high-resolution spectroscopy. We find that the average uncertainties of chemical composition, which are reported as ${\rm X/Fe}$ ratios, are only 10%–20%. The ${\rm X/Fe}$ abundance pattern of the Ophiuchus centre is remarkably consistent with solar, which is reminiscent of the Hitomi constraint on the Perseus core. The observed abundance pattern can be replicated globally by linear combination models of core-collapse, including massive progenitors, and Type Ia supernovae. While nucleosynthesis models typically underestimate the ${\rm Ca/Fe}$ ratio, a substantial contribution of Ca-rich gap transients may help improve the deficit of Ca. High-resolution spectroscopic data can enable us to estimate the underlying impact on the chemical enrichment from subclasses of Type Ia supernovae.