On the soft X-ray spectrum of cooling flows

By A. C. Fabian, R. Mushotzky, P. Nulsen, J. R. Peterson. 2000

132 citations recorded by the source corpus.

Strong evidence for cooling flows has been found in low-resolution X-ray imaging and spectra of many clusters of galaxies. However, high-resolution X-ray spectra of several clusters from the Reflection Grating Spectrometer on XMM-Newton now show a soft X-ray spectrum inconsistent with a simple cooling flow. The main problem is a lack of the emission lines expected from gas cooling below 1–2 keV. Lines from gas at about 2–3 keV are observed, even in a high-temperature cluster such as A1835, indicating that gas is cooling down to about 2–3 keV, but is not found at lower temperatures. Here we discuss several solutions to the problem: heating, mixing, differential absorption and inhomogeneous metallicity. Continuous or sporadic heating creates further problems, including the targeting of the heat at the cooler gas and also the high total energy required. So far there is no clear observational evidence for widespread heating, or shocks, in cluster cores, except in radio lobes which occupy only part of the volume. Alternatively, if the metals in the intracluster medium are not uniformly spread but are clumped, then little line emission is expected from the gas cooling below 1 keV. The low-metallicity part cools without line emission, whereas the strengths of the soft X-ray lines from the metal-rich gas depend on the mass fraction of that gas and not on the abundance, since soft X-ray line emission dominates the cooling function below 2 keV.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/bf7b0dd72181421445eb6ba9d33e9d13335bacab

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Instrumentation

Citations in the corpus

The dependence of star formation history and internal structure on stellar mass for 105 low‐redshift galaxies (2002, background): “…halo mass. Clues as to why this is the case may come from recent Chandra and XMM observations, which show that cooling of gas to temperatures below 1 keV is suppressed at the centres of rich clusters, where the most massive ellipticals are located (e.g. Fabian et al 2001; Bohringer et al 2001).”
Chandra observations of Abell 2199 (2002, background): “It may be heated, mixed with much cooler gas or expelled (see e.g. Fabian et al. 2001b).”
Spatially resolved X-ray spectroscopy of cooling clusters of galaxies (2003, unknown): “Worked-out examples include metallicity inhomogeneities (Fabian et al. 2001), buoyantly rising radio bubbles transporting cool gas outwards (Churazov et al. 2001), halo-in-halo structure (Makishima et al. 2001), turbulent mixing due to rising and falling hot gas bubbles (Quilis et al. 2001),…”
Thermal conduction and reduced cooling flows in galaxy clusters (2003, background): “…models which preserve the classic mass deposition rates by invoking differential absorption, mixing or inhomogeneous metallicity distributions (Fabian et al. 2001; Morris & Fabian 2002; Fabian et al. 2002a), and those which prevent, or significantly reduce, mass dropout by balancing the…”
Thermal Conduction in Clusters of Galaxies (2001, background): “Only perturbations on the scale lB cause strong mirroring, but these have a negligible effect so long as λ < lB (Chandran et al. 1999; Malyshkin & Kulsrud 2001).”
High-Resolution X-Ray Spectroscopic Constraints on Cooling-Flow Models for Clusters of Galaxies (2002, methodology): “—Begelman & Fabian (1990) and Fabian et al. (2001) discussed the possibility that hot electrons are cooled conductively by interfaces with cold clouds.”
Heating cooling flows with jets (2003, background): “These included strong internal absorption (Allen & Fabian 1997), magnetic locking of overdense regions (Tribble 1989; Balbus 1991), abundance anomalies (Fabian et al. 2001; Morris & Fabian 2003), and conduction of heat from large to small radii (Bertschinger & Meiksin 1986; Narayan & Medvedev 2001).”
Hydrodynamical simulations of cluster formation with central AGN heating (2005, background): “However, up to the present time, optical and X-ray observations have failed to detect the required amount of this cool gas, suggesting that it is simply not there (e.g. McNamara et al. 2000; Tamura et al. 2001; Balogh et al. 2001; Kaastra et al. 2001; Fabian et al. 2001; C© 2005 The Authors.”
The hydrodynamics of dead radio galaxies (2002, background): “Fabian et al. (2001) discusses various solutions for this puzzle and favours a model in which there are large abundance inhomogenieties affecting the predicting cooling rates.”
A deep Chandra observation of the Perseus cluster: shocks and ripples (2003, background): “Other possibilities involving inhomogeneous metallicity (Fabian et al. 2001; Morris & Fabian 2003) and mixing with cooler gas (Fabian et al. 2001, 2002b) remain.”
The Cluster-Scale AGN Outburst in Hydra A (2004, background): “While they face some difficulties (e.g. Fabian et al. 2001), AGN heating models provide a natural feedback mechanism, making them the strongest candidate to solve this cooling flow problem.”
Cooling flows as a calorimeter of active galactic nucleus mechanical power (2002, background): “One possible example of such a filament may be found in A1795 (Cowie et al. 1983, Fabian et al. 2001).”
Energy, momentum and mass outflows and feedback from thick accretion discs around rotating black holes (2013, background): “…much shorter than the age of the system, suggesting that gas at the centres of these clusters must condense and turn into stars; however, there is no observational evidence for star formation at the required level (Fabian et al. 2001; Peterson et al. 2003; Kaastra et al. 2004; Croton et al. 2006).”
Hot Gas In and Around Elliptical Galaxies (2003, background): “The spectral contributions of cooling gas can be reduced if X-ray emission from the cooling gas is absorbed or if the cooling is more rapid than normal radiative cooling (Peterson et al. 2001; Fabian et al. 2001).”
Raining on black holes and massive galaxies: the top-down multiphase condensation model (2016, background): “While the adopted cooling curve is customary in the literature, we note other types of cooling may be at work, such as the mixing layers proposed by Fabian et al. (2001).”
Enhancement and Suppression of Heat Transfer by MHD Turbulence (2006, background): “The latter problem has been subjected to particular scrutiny as observations do not support the evidence for the cool gas (see Fabian et al. 2001).”
How do galaxies populate dark matter haloes (2009, background): “The inefficiency of star formation at the centre of massive halos is related to the well known “cooling flow paradox” (e.g. Fabian et al. 2001).”
The detection of molecular gas in the central galaxies of cooling flow clusters (2001, background): “This galaxy has an unusual optical line emission filament (see Fabian et al. 2001a) so further CO observations are necessary to search for similarly extended molecular gas.”
Heating Hot Atmospheres with Active Galactic Nuclei (2007, background): “Processes such as gas-phase mixing, differential photoelectric absorption, and rapidly cooling, unresolved, high metallicity inclusions in the hot gas (Fabian et al. 2001) are possible.”