High‐Resolution X‐Ray Spectroscopic Constraints on Cooling‐Flow Models for Clusters of Galaxies

Abstract

We present high resolution X-ray spectra of 14 putative cooling-flow clusters of galaxies obtained with the Reflection Grating Spectrometer on XMM-Newton. The clusters in the sample span a large range of temperatures and mass deposition rates. Various of these spectra exhibit line emission from O VIII, Ne X, Mg XII & XI, Al XIII & XII, Si XIV & XIII, N VII, and C VI as well as all Fe L ions. The spectra exhibit strong emission from cool plasma at just below the ambient temperature, T 0 , down to T 0 /2, but also exhibit a severe deficit of emission, relative to the predictions of the isobaric cooling-flow model at lower temperatures (< T 0 /3). In addition, the bestresolved spectra show emission throughout the entire X-ray temperature range, but increasingly less emission at lower temperatures than the cooling-flow model would predict.These results are difficult to reconcile with simple prescriptions for distorting the emission measure distribution, e.g. by including additional heating or rapid cooling terms. We enumerate some theoretical difficulties in understanding the soft X-ray spectra of cooling-flows independent of the classic problem of the failure to detect the cooling-flow sink. Empirically, the differential luminosity distribution is consistent with being proportional to the temperature to the power of ≈ 1 to 2, instead of being independent of the temperature, as expected in the standard multi-phase model. The primary differences in the observed low temperature spectra are ascribed to differences in the ambient temperature.

Implications of a variable IMF for the interpretation of observations of galaxy populations

“…The large gas accretion rates may be inconsistent with X-ray observations of galaxy clusters (e.g. Peterson et al 2003). Combining the high-end Table 1.…”

AGN jet-driven stochastic cold accretion in cluster cores

“…In fact, the largest molecular gas mass occurs in the hottest cluster, unlike what is expected from T −3/2 keV scaling ofṀB (Eq. 1; this assumes that the temperature of the hot gas at the Bondi radius scales with the core Xray temperature; X-ray spectra do not show X-ray emitting gas below 0.3 the cluster temperature; e.g., Peterson et al 2003; see also Fig. 1a of Hogan et al 2016).…”

Scaling Relations for Galaxy Clusters: Properties and Evolution

“…Given the short gas cooling time this should lead to significant star formation, which is not observed; nor is the cold gas (e.g. Kaastra et al 2001;Peterson et al 2003). A solution can be provided by a suitable scheme of gas heating that compensates for the radiative losses, pressurizes the gas in the core regions, and regulates star formation.…”