High-resolution X-ray spectroscopy with XRISM/Resolve reveals super-Solar abundance ratios in Virgo/M87

TL;DR

This study uses high-resolution X-ray spectroscopy from XRISM/Resolve to measure elemental abundances in the Virgo cluster core, revealing super-Solar ratios and spatial variations that inform its enrichment history.

Contribution

First detailed XRISM/Resolve measurements of multiple elemental abundances in Virgo/M87, showing super-Solar ratios and spatially resolved chemical enrichment patterns.

Findings

All four Virgo core regions show super-Solar X/Fe ratios.

Cool, metal-rich gas coexists with hotter ambient ICM.

Super-Solar ratios are consistent across models and robust against analysis variations.

Abstract

The chemical composition of the intracluster medium (ICM) provides key insights into the enrichment history of galaxy clusters. However, high-resolution abundance measurements with X-ray microcalorimeters remain available for only a few systems. While most cool-core clusters exhibit near-Solar elemental abundance ratios relative to Fe, previous studies of the Virgo cluster suggested super-Solar ratios in its core. We investigate the chemical properties of the Virgo cluster core using XRISM/Resolve observations, focusing on precise measurements of Si, S, Ar, Ca, Cr, Fe, and Ni abundances. We aim to determine whether Virgo displays abundance patterns distinct from other nearby cool-core clusters and to explore the origin of any differences. We analysed XRISM/Resolve spectra in four regions of the Virgo core (center, east, northwest, and southwest) in the 1.7-11 keV band. Single-temperature, multi-temperature, and multi-abundance models were applied to characterize the thermal structure and derive elemental abundances. The resulting abundance ratios were compared between pointings, with previous studies of Virgo/M87, and with recent XRISM measurements of other clusters. All four pointings exhibit systematically super-Solar X/Fe ratios, although the northwest region shows values closer to Solar. Multi-abundance modeling of the eastern and southwestern regions reveals that cool, metal-rich gas uplifted by the AGN coexists with a hotter, more chemically homogeneous ambient ICM. The super-Solar ratios are robust against variations in bandpass and temperature structure. We interpret these enhanced ratios as reflecting the enrichment history of the old stellar population in M87 combined with a limited cold gas reservoir. The Virgo core exhibits spatially resolved chemical enrichment that differs from the abundance patterns observed in other cool-core clusters.