Hidden Cooling Flows in clusters of Galaxies II: a wider sample

We have recently uncovered Hidden Cooling Flows (HCFs) in the XMM Reflection Grating Spectrometer spectra of three clusters of galaxies; Centaurus, Perseus, and A1835. Here, we search for them in a wider sample of objects: the X-ray brightest group NGC 5044; four moderate X-ray luminosity clusters Sersic 159, A262, A2052, and RX J0821; and three high X-ray luminosity clusters RX J1532, MACS 1931, and the Phoenix cluster. Finally, we examine two Virgo elliptical galaxies, M49 and M84. All statistically allow the addition of an HCF. We find a significant detection of an HCF in six clusters and two elliptical galaxies. The hidden mass cooling rates are 5 -40 M-? yr(-1) for the normal clusters, 1000 M-? yr(-1) or more for the extreme clusters, and 1 -2 M-? yr(-1) for the elliptical galaxies. We discuss the implications of the results for the composition of the innermost parts of the massive host galaxies and look forward to future observations.

Automated summary

We have discovered Hidden Cooling Flows (HCFs) in the spectra of three clusters of galaxies using the XMM Reflection Grating Spectrometer. We extended our search to a wider sample of objects and found HCFs in six clusters and two elliptical galaxies. The cooling rates vary from 5-40 M-? yr(-1) for normal clusters, over 1000 M-? yr(-1) for extreme clusters, and 1-2 M-? yr(-1) for elliptical galaxies. The implications of these findings for the composition of galaxies' innermost parts are discussed, and further observations are anticipated.