Metal transport by gas sloshing in M87

TL;DR

This study uses X-ray observations to analyze a cold front in M87, revealing how gas sloshing transports metals like iron within the Virgo cluster's core, with implications for understanding cluster evolution.

Contribution

It provides the first quantitative estimate of iron mass transported by a cold front, highlighting the role of sloshing in metal redistribution in galaxy clusters.

Findings

Gas sloshing creates a cold front with a metallicity discontinuity.

Approximately 6% of the Fe mass within the affected region is transported by the cold front.

Fe abundance outside the front is very low (~0.2 solar), indicating transport of enriched gas into pristine regions.

Abstract

We present the results of an XMM-Newton mosaic covering the central ~200 kpc of the nearby Virgo cluster. We focus on a strong surface brightness discontinuity in the outskirts of the brightest cluster galaxy, M87. Using both XMM-Newton and Suzaku, we derive accurate temperature and metallicity profiles across this feature and show that it is a cold front probably due to sloshing of the Virgo ICM. It is also associated with a discontinuity in the chemical composition. The gas in the inner, bright region of the front is ~40% more abundant in Fe than the gas outside the front, suggesting the important role of sloshing in transporting metals through the ICM. For the first time, we provide a quantitative estimate of the mass of Fe transported by a cold front. This amounts to ~6% of the total Fe mass within the radial range affected by sloshing, significantly more than the amount of metals transported by the AGN in the same cluster core. The very low Fe abundance of only ~0.2 solar immediately outside the cold front at a radius of 90 kpc suggests we are witnessing first-hand the transport of higher metallicity gas into a pristine region, whose abundance is typical of the cluster outskirts. The Mg/Fe and O/Fe abundance ratios remain approximately constant over the entire radial range between the centre of M87 and the faint side of the cold front, which requires the presence of a centrally peaked distribution not only for Fe but also for core-collapse type supernova products. This peak may stem from the star formation triggered as the BCG assembled during the protocluster phase.