Imaging-spectroscopy diagnosis of the giant sloshing spiral in the Virgo cluster with the Einstein Probe Follow-up X-ray Telescope

¹ State Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
² School of Physics and Astronomy, Beijing Normal University, Beijing 100875, China
³ Department of Astronomy, Tsinghua University, Beijing 100084, China
⁴ Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
⁵ Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University, Beijing 102206, China
⁶ National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Beijing 100101, China
⁷ Department of Astronomy, Xiamen University, Xiamen 361005, China
⁸ School of Astronomy and Space Science, University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, China
⁹ Computing Center, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China

^⋆ Corresponding author: xyzheng@ihep.ac.cn

Received: 24 March 2025
Accepted: 5 July 2025

Abstract

We performed deep X-ray observations of the Virgo cluster using the Einstein Probe Follow-up X-ray Telescope (EP-FXT) with a total exposure of 295 ks. Taking advantage of the large field of view (FoV) and low particle background of EP-FXT, the image reveals a giant spiral feature connecting the cold fronts in the northwest and southeast, forming a coherent structure consistent with previous XMM-Newton and Suzaku findings. Furthermore, we present two-dimensional maps of the temperature, metallicity, and entropy in the Virgo cluster that cover a FoV of approximately 28.5′. These maps clearly depict a spiral structure that is characterized by high density, low temperature, high metallicity, and low entropy. These results support the scenario in which the spiral morphology originates from gas sloshing that is induced by a minor merger. In addition, the temperatures measured with EP-FXT are reasonably consistent with those obtained from XMM-Newton within the uncertainties.