Impact of magnetic field on the gas mass fraction of galaxy clusters

TL;DR

This study investigates how magnetic fields influence the gas mass fraction in galaxy clusters, finding a modest impact of about 1% due to magnetic pressure, with potential for more precise future measurements.

Contribution

The paper quantifies the effect of magnetic fields on gas mass fraction estimates in galaxy clusters using observationally motivated magnetic profiles and hydrostatic equilibrium.

Findings

Magnetic fields reduce the estimated gas mass fraction by about 1%.

The impact depends on magnetic field strength and profile.

Future observations like SKA can improve these estimates.

Abstract

Magnetic fields have been observed in galaxy clusters with strengths of the order of $\sim \mu$G. The non-thermal pressure exerted by magnetic fields also contributes to the total pressure in galaxy clusters and can in turn affect the estimates of the gas mass fraction, $f_{gas}$. In this paper, we have considered a central magnetic field strength of $5\mu$G, motivated by observations and simulations of galaxy clusters. The profile of the magnetic field has also been taken from the results obtained from simulations and observations. The role of magnetic field has been taken into account in inferring the gas density distribution through the hydrostatic equilibrium condition (HSE) by including the magnetic pressure. We have found that the resultant gas mass fraction is smaller with magnetic field as compared to that without magnetic field. However, this decrease is dependent on the strength and the profile of the magnetic field. We have also determined the total mass using the NFW profile to check for the dependency of $f_{gas}$ estimates on total mass estimators. From our analysis, we conclude that for the magnetic field strength that galaxy clusters seem to possess, the non-thermal pressure from magnetic fields has an impact of $\approx 1~\%$ on the gas mass fraction of galaxy clusters. However, with upcoming facilities like Square Kilometre Array (SKA), it can be further expected to improve with more precise observations of the magnetic field strength and profile in galaxy clusters, particularly in the interior region.