Constraints on turbulent velocity broadening for a sample of clusters, groups and elliptical galaxies using XMM-Newton

TL;DR

This study uses XMM-Newton spectra to constrain turbulent velocities in the cores of galaxy clusters, groups, and ellipticals, finding most have low turbulence levels below 700 km/s, with some showing even lower velocities.

Contribution

First direct constraints on turbulent velocities in galaxy cluster cores using XMM-Newton spectral line widths, including methods to account for spatial broadening effects.

Findings

Five objects have upper limits on line-of-sight broadening of 500 km/s.

Half of the objects have an upper limit below 700 km/s.

At least 15 sources have turbulence energy less than 20% of thermal energy.

Abstract

Using the width of emission lines in XMM-Newton Reflection Grating Spectrometer spectra, we place direct constraints on the turbulent velocities of the X-ray emitting medium in the cores of 62 galaxy clusters, groups and elliptical galaxies. We find five objects where we can place an upper limit on the line-of-sight broadening of 500 km/s (90 per cent confidence level), using a single thermal component model. Two other objects are lower than this limit when two thermal components are used. Half of the objects examined have an upper limit on the velocity broadening of less than 700 km/s. To look for objects which have significant turbulent broadening, we use Chandra spectral maps to compute the expected broadening caused by the spatial extent of the source. Comparing these with our observed results, we find that Klemola 44 has extra broadening at the level of 1500 km/s. RX J1347.5-1145 shows weak evidence for turbulent velocities at 800 km/s. In addition we obtain limits on turbulence for Zw3146, Abell 496, Abell 1795, Abell 2204 and HCG 62 of less than 200 km/s. After subtraction of the spatial contribution and including a 50 km/s systematic uncertainty, we find at least 15 sources with less than 20 per cent of the thermal energy density in turbulence.