New $\beta$ Model of Intracluster Gas Distribution

TL;DR

This paper introduces a new $eta$ model for intracluster gas distribution using the exact King model, improving fit to X-ray data and resolving mass discrepancies without invoking cooling flows.

Contribution

The new model employs the exact King model instead of approximate dark matter profiles, providing better fit and insight into intracluster gas and mass distribution.

Findings

Model fits observed X-ray profiles well except outermost regions.

Central mass concentration explains lensing and X-ray mass discrepancies.

$eta$ values support non-gravitational heating theories.

Abstract

A new type of $\beta$ model of intracluster gas distribution is established, which is well fitted to the observed X-ray surface brightness profile except for outermost region. It employs the exact King model of the self-gravitating system of collisionless particles instead of the widely used approximated analytical formula for the dark matter distribution. The small difference between the modelled and the observed X-ray surface brightness profiles would disappear if the infall of matter from the intercluster space is taken into account. The number of parameters of our model is the same as for the isothermal $\beta$ model, but the agreement between our model and data points is satisfactory even when the fitting with the isothermal $\beta$ model remains a large central excess. In addition, the enhanced central mass concentration in our model is high enough to resolve the discrepancy between the X-ray and the lensing measurements of cluster mass. These facts suggest that most of the central excess might be no more than a ghost embossed by an inadequate fitting. Therefore the central excess would not necessarily be linked to the existence of cooling flow. It is also shown that the obtained values of $\beta$ (our model) ~ 0.5 support the theory of non-gravitational intracluster gas heatings comparable to those reached through gravitational collapse. On the other hand, the value of $\beta$ ~ 0.6 obtained for the isothermal $\beta$ model is explained as showing the scarcity of matter in the space surrounding each cluster, brobably due to the infall of matter towards it over a long time.