Is the Gas in Cooling Flows Multiphase?

Abstract

Employing XMM-Newton EPIC data we perform a detailed comparison between different spectral models to test whether the gas in cooling-flows is multi-phase or not. Our findings all point in the same direction, namely that gas in cooling-flows does not show the wide distribution of temperatures expected from standard multi-phase models. This result has profound implications for cooling-flow models. Firstly, the large absorption column depths inferred by previous analysis of cooling-flow spectra are most likely an artifact following from the application of an incorrect spectral model to the data. Secondly, the mass deposition and mass flow are likely to be much smaller than previously thought. Last, but perhaps not least, the term "cooling-flow" cluster is probably no longer appropriate, as it describes a phenomenon of smaller entity and impact than previously thought. We propose to substitute it with that of "cool-core" cluster. The latter definition is less ambitious than the first, as it reflects only an observational fact rather than an inferred physical property, the flow, but has the undeniable advantage of being firmer.

Abundance Gradients and the Role of Supernovae in M87

“…This model has 15 free parameters, as does the 2T model, because the maximum temperature T max is tied to the vmekal component temperature. As indicated in recent papers (Molendi & Pizzolato 2001;Molendi & Gastaldello 2001), this model is used to describe a scenario that is different from a multiphase gas, which it was written for; the gas is all at one temperature, and the multiphase appearance of the spectrum comes from the projection of emission from many different physical radii. A more correct description will be given by a real deprojection of the spectrum (F. Pizzolato et al 2002, in preparation).…”

Models of Galaxy Clusters with Thermal Conduction

“…Recent high-resolution X-ray data from XMM-Newton and Chandra indicate that there is no evidence for the multitemperature gas that one expects if there is substantial mass dropout Tamura et al 2001;Bö hringer et al 2001;Fabian et al 2001;Molendi & Pizzolato 2001;Matsushita et al 2002;Johnstone et al 2002). The new data strongly suggest that mass dropout must be prevented by some additional source of heat that balances radiative losses.…”

Nonthermal support for the outer intracluster medium

“…In preparation for the developments given below, we stress that the few parameters specifying k(r) are enough for the SM to provide remarkably good fits to the detailed X-ray data on surface brightness and on temperature profiles of many clusters (see Fusco-Femiano et al 2009). These include central temperature profiles of both main classes identified by Molendi & Pizzolato (2001): the cool-cored CCs with a central dip and the centrally flat, non-cool-cored NCCs. The SM intrinsically links these morphologies to low or high entropy levels of k c ∼ 10 1 or ∼10 2 keV cm 2 , respectively, and they are conceivably imprinted by energy inputs from central AGN outbursts or from deep mergers Fusco-Femiano et al 2009).…”