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

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, MACS J2229.7-2755, gives a velocity limit of 280 km s^{-1} at the 90 per cent confidence level. Other systems with limits close to 300 km s^{-1} include A 1835, NGC 4261 and NGC 4472. For more than a third of the targets we find limits better than 500 km s^{-1} . HCG 62, NGC 1399 and A 3112 show evidence for {∼ } 400 km s^{-1} 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^{-1} ), we find broadening at the level of 280 to 500 km s^{-1} in A 3112, NGC 1399 and NGC 4636.