By J.M. Kempf

The hot intracluster medium (ICM) plasma is thought to be in a poorly understood dilute, magnetised regime that may give rise to a variety of astrophysically important dynamical plasma effects regulating its internal transport and heating. The most promising candidate for detection is the magneto-thermal instability (MTI), which could drive thermal turbulence at resolved scales (~hundreds of kiloparsec) in the outskirts of galaxy clusters, where the background temperature outwardly decreases. As the Athena/X-IFU instrument will enable direct and spatially-resolved maps of the internal dynamics of the ICM, could it notably detect the MTI?

In this paper, we assessed the typical strength, scales and possible detectability of this magneto-convective dynamics. Our results suggest that in bright enough regions of galaxy clusters amenable to observations,  turbulent fluctuations induced by the magneto-thermal instability may at best only be marginally detectable with the X-IFU — the level of the MTI-driven turbulence only gets large enough in external regions that are too dim even for the very large collecting area of the Athena mirrors. Finding direct signatures of magnetised plasma dynamics in the ICM, even at large observable scales typical of the MTI, therefore remains challenging.

Access to the manuscript in ADS.