Further X-ray observations of the galaxy cluster PKS 0745-191 to the virial radius and beyond

TL;DR

This study uses improved Suzaku X-ray observations to accurately measure the thermodynamic properties of galaxy cluster PKS 0745-191 out to 1.25 times its virial radius, addressing previous background modeling issues.

Contribution

It provides the first detailed thermodynamic profiles of PKS 0745-191 beyond the virial radius with enhanced accuracy and resolves prior discrepancies caused by background modeling errors.

Findings

Entropy profile flattens in outskirts, starting at larger radius than previously observed.

Outside ~17' (~1.9 Mpc), the ICM shows signs of non-hydrostatic equilibrium.

Results suggest significant non-thermal pressure support in the cluster outskirts.

Abstract

We use new Suzaku observations of PKS 0745-191 to measure the thermodynamic properties of its ICM out to and beyond r_{200} (reaching 1.25r_{200}) with better accuracy than previously achieved, owing to a more accurate and better understood background model. We investigate and resolve the tensions between the previous Suzaku and ROSAT results for PKS 0745-191, which are found to be principally caused by incorrect background modelling in the previous Suzaku analysis. We investigate in depth the systematic errors affecting this observation, and present temperature, density, entropy and gas mass fraction profiles reaching out to and beyond the virial radius. We find that the entropy profile flattens in the outskirts as originally observed in the previous Suzaku analysis, but that the flattening starts at larger radius. The flattening of the entropy profile and our mass analysis suggests that outside ~17' (~1.9 Mpc) the ICM is out of hydrostatic equilibrium or the presence of significant non-thermal pressure support.