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arXiv · 2609.35330

ViCTORIA project: A pilot study of the M49 region in the Virgo cluster in polarisation

A. Spasic·A. Benati·M. Brüggen·H. W. Edler·F. De Gasperin·V. Gustafsson·P. Serra·A. Bonafede·A. Boselli·H. McCall
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Abstract

Large-scale magnetic fields permeate the Intracluster Medium (ICM) of galaxy clusters. Understanding these fields gives an insight into the origin of cosmic magnetic fields and the interaction of cluster galaxies with the ICM. Using MeerKAT observations of the Virgo cluster as part of the ViCTORIA project, we probe magnetic fields via Rotation Measure (RM) synthesis. The aim of this work is to characterise the magnetic fields in and around the infalling group M49 in the Virgo cluster. We will probe the interaction of M49 with its surrounding medium through its imprint on the polarised emission and Faraday rotation. We use L-band MeerKAT data in full polarisation calibrated with the ViCTORIA MeerKAT Survey (ViMS) pipeline, which is designed for the calibration, imaging, mosaicking and RM Synthesis of the fields in the Virgo cluster, to achieve high-fidelity reconstruction of, both, total intensity and polarised emission. We analyse the background sources of the cluster for potential local changes in the magnetic field, by calculating the RM distribution. In the final polarised image, consisting of four pointings of 45 min, we reach a noise level of $23.3 μ\textrm{Jy/beam}$. We detect 101 background sources in the $\sim 2.5\, \textrm{deg}^2$ region around M49, corresponding to a source density of 40 sources/$ \textrm{deg}^2$. Across the $112\, \textrm{deg}^2$ observations of the Virgo cluster, this implies a total number of 4000 polarised sources. In M49 we find structured, diffuse polarised emission extending in the direction of the total intensity radio tails. A higher polarisation fraction across the upper edge of the source indicates the effect of magnetic field draping. Around M49 we find a larger RM scatter (at $3.8σ$) in the wake of M49 compared to the region in front of it. This can inform the modelling of the turbulence created by galactic motions.

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A. Spasic, A. Benati, M. Brüggen, H. W. Edler, F. De Gasperin, V. Gustafsson, P. Serra, A. Bonafede, A. Boselli, H. McCall. 2026-09-28. ViCTORIA project: A pilot study of the M49 region in the Virgo cluster in polarisation. https://arxiv.org/abs/2609.35330

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