A direct limit on the turbulent velocity of the intracluster medium in the core of Abell 1835 from XMM-Newton

TL;DR

This study uses XMM-Newton RGS data to set the first direct limits on turbulent velocities in the core of galaxy cluster Abell 1835, constraining non-thermal motions and cooling gas properties.

Contribution

It provides the first direct measurement of turbulent velocity limits in a galaxy cluster core using high-resolution X-ray spectroscopy.

Findings

Turbulent velocity upper limit is 274 km/s within 30 kpc.

Turbulent energy density is less than 13% of thermal energy.

Cooling gas below 3.85 keV is limited to 140 solar masses per year.

Abstract

We examine deep XMM-Newton Reflection Grating Spectrometer (RGS) observations of the X-ray luminous galaxy cluster A1835. For the first time in a galaxy cluster we place direct limits on turbulent broadening of the emission lines. This is possible because the coolest X-ray emitting gas in the cluster, which is responsible for the lines, occupies a small region within the core. The most conservative determination of the 90 per cent upper limit on line-of-sight, non-thermal, velocity broadening is 274 km/s, measured from the emission lines originating within 30 kpc radius. The ratio of turbulent to thermal energy density in the core is therefore less than 13 per cent. There are no emission lines in the spectrum showing evidence for gas below ~3.5 keV. We examine the quantity of gas as a function of temperature and place a limit of 140 Msun/yr (90 per cent) for gas cooling radiatively below 3.85 keV.