Velocity width measurements of the coolest X-ray emitting material in the cores of clusters, groups and elliptical galaxies

TL;DR

This study measures the velocity broadening of cool X-ray emitting gas in galaxy clusters, groups, and ellipticals using advanced spectral modeling, revealing velocities mostly below 500 km/s and providing new constraints on gas motions.

Contribution

It introduces an improved spectral model that accounts for spatial broadening and applies both conventional and MCMC methods to better constrain velocity widths in X-ray emitting gas.

Findings

Velocity limits often below 500 km/s in studied systems.

Detection of ~400 km/s velocity broadening in some targets.

Systematic errors around 150 km/s in surface brightness profile method.

Abstract

We examine the velocity width of cool X-ray emitting material using XMM-Newton Reflection Grating Spectrometer (RGS) spectra of a sample of clusters and group of galaxies and elliptical galaxies. Improving on our previous analyses, we apply a spectral model which accounts for broadening due to the spatial extent of the source. With both conventional and Markov Chain Monte Carlo approaches we obtain limits, or in a few cases measurements, of the velocity broadening of the coolest X-ray material. In our sample, we include new observations targeting objects with compact, bright, line-rich cores. One of these, MACSJ2229.7-2755, gives a velocity limit of 280 km/s at the 90 per cent confidence level. Other systems with limits close to 300 km/s include A1835, NGC4261 and NGC4472. For more than a third of the targets we find limits better than 500 km/s. HCG62, NGC1399 and A3112 show evidence for ~400 km/s velocity broadening. For a smaller sample of objects, we use continuum-subtracted emission line surface brightness profiles to account for the spatial broadening. Although there are significant systematic errors associated with the technique (~150 km/s), we find broadening at the level of 280 to 500 km/s in A3112, NGC1399 and NGC4636.