Measuring sloshing, merging and feedback velocities in the Virgo cluster

TL;DR

This study uses advanced X-ray calibration techniques to map the velocity structure of the Virgo cluster, revealing complex gas motions including outflows, backflows, and sloshing effects.

Contribution

It introduces a novel calibration method for precise velocity measurements and provides detailed 2D velocity maps of the Virgo cluster.

Findings

Detection of high-velocity outflows near the AGN

Identification of gas backflows in radio lobes

Observation of velocity gradients indicating sloshing

Abstract

We present a detailed analysis of the velocity structure of the Virgo cluster using {\it XMM-Newton} observations. Using a novel technique which uses uses the Cu K$\alpha$ instrumental line to calibrate the EPIC-pn energy scale, we are able to obtain velocity measurements with uncertainties down to $\Delta v \sim 100$ km/s. We created 2D projected maps for the velocity, temperature, metallicity, density, pressure and entropy with an spatial resolution of 0.25$'$. We have found that in the innermost gas there is a high velocity structure, most likely indicating the presence of an outflow from the AGN while our analysis of the cluster cool core using RGS data indicates that the velocity of the gas agrees with the M87 optical redshift. An overall gradient in the velocity is seen, with larger values as we move away from the cluster core. The hot gas located within the western radio flow is redshifted, moving with a velocity $\sim 331$ km/s while the hot gas located within the eastern radio flow is blueshifted, with a velocity $\sim 258$ km/s, suggesting the presence of backflows. Our results reveal the effects of both AGN outflows and gas sloshing, in the complex velocity field of the Virgo cluster.