Searching for cool and cooling X-ray emitting gas in 45 galaxy clusters and groups

Abstract

We present a spectral analysis of cool and cooling gas in 45 cool-core clusters and groups of galaxies obtained from Reflection Grating Spectrometer (RGS) XMM-Newton observations. The high-resolution spectra show Fe XVII emission in many clusters, which implies the existence of cooling flows. The cooling rates are measured between the bulk Intracluster Medium (ICM) temperature and 0.01 keV and are typically weak, operating at less than a few tens of M yr −1 in clusters, and less than 1 M yr −1 in groups of galaxies. They are 10-30% of the classical cooling rates in the absence of heating, which suggests that AGN feedback has a high level of efficiency. If cooling flows terminate at 0.7 keV in clusters, the associated cooling rates are higher, and have a typical value of a few to a few tens of M yr −1 . Since the soft X-ray emitting region, where the temperature kT < 1 keV, is spatially associated with Hα nebulosity, we examine the relation between the cooling rates above 0.7 keV and the Hα nebulae. We find that the cooling rates have enough energy to power the total UV-optical luminosities, and are 5 to 50 times higher than the observed star formation rates for low luminosity objects. In 4 high luminosity clusters, the cooling rates above 0.7 keV are not sufficient and an inflow at a higher temperature is required. Further residual cooling below 0.7 keV indicates very low complete cooling rates in most clusters.On the contrary, observations have shown that the star formation rate is only a small fraction of the predicted coolc 2018 RAS arXiv:1902.03826v1 [astro-ph.HE]

The inner gas mass–temperature profile in the core of nearby galaxy clusters

“…The lifetime are of course longer if AGN heating acts on these components. Note that in the Perseus cluster, we measured a higher cooling rate from a larger 99% PSF core spectrum (Liu et al 2019).…”

“…We find a further component at 0.2 keV usually gives an upper limit. Resonant scattering of Fe XVII lines also leads to degeneracy in the emission measure of the 0.2 and 0.7 keV components as found in some clusters in the CHEERS sample (Pinto et al 2015;Liu et al 2019). Therefore we only use the three-component model in this work.…”

“…The existence of gas at all X-ray temperatures suggests the inexact balance between the cooling and AGN heating. The cooling rates deduced from RGS spectra are very low, typically less than 10% of the predicted rates in the absence of heating (Liu et al 2019). Some cooling is presumably necessary, if the central supermassive black hole is powered by gas accretion and a sustaining accretion-feedback loop.…”

“…It is then convolved with the line broadening (lpro) component in SPEX. These settings except binning are the same as Liu et al (2019).…”

Lessons learned from 19 years of high‐resolution X‐ray spectroscopy of galaxy clusters with the reflection grating spectrometer on board XMM‐Newton

“…The comparison of the cooling rates measured by RGS with the results obtained at lower energies is a key to unveiling the evolution of the ICM. For instance, Liu et al () used RGS observations for a sub‐sample of the CHEERS catalog plus A 1835 and confirmed that the cooling rates are an order of magnitude lower than the theoretical predictions. However, they also showed that the cooling rates may still be high enough to explain the H α luminosity and the star formation rates measured with the Hubble Space Telescope and WISE.…”