Modified Entropy Models for the Intracluster Medium

By G. Mark Voit, Greg L. Bryan, M. Balogh, Richard G. Bower. 2002

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We present a set of cluster models that link the present-day properties of clusters to the processes that govern galaxy formation. These models treat the entropy distribution of the intracluster medium as its most fundamental property. Because convection strives to establish an entropy gradient that rises with radius, the observable properties of a relaxed cluster depend entirely on its dark matter potential and the entropy distribution of its uncondensed gas. Guided by simulations, we compute the intracluster entropy distribution that arises in the absence of radiative cooling and supernova heating by assuming that the gas density distribution would be identical to that of the dark matter. The lowest entropy gas would then fall below a critical entropy threshold at which the cooling time equals a Hubble time. Radiative cooling and whatever feedback is associated with it must modify the entropy of that low-entropy gas, changing the overall entropy distribution function and thereby altering the observable properties of the cluster. Using some phenomenological prescriptions for entropy modification based on the existence of this cooling threshold, we construct a remarkably realistic set of cluster models. The surface brightness profiles, mass-temperature relation, and luminosity-temperature relation of observed clusters all naturally emerge from these models. By introducing a single adjustable parameter related to the amount of intracluster gas that can cool within a Hubble time, we can also reproduce the observed temperature gradients of clusters and the deviations of cooling flow clusters from the standard luminosity-temperature relation.

Subfields: Astronomy and Astrophysics, Instrumentation, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/f1c8b7f65dd5a1ff1324208bf3c0e9a6a96fcc7d

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Citations in the corpus

Cosmological constraints from the local X-ray luminosity function of the most X-ray-luminous galaxy clusters (2002, background): “This highlights the likely importance of additional physics such as cooling and pre-heating in the intracluster gas (see also Pearce et al. 2000; Thomas et al. 2002; Voit et al. 2002; Muanwong et al. 2002).”
Gas expulsion by quasar-driven winds as a solution to the overcooling problem in galaxy groups and clusters (2010, background): “In the language of VB, radiative cooling ‘truncates’ the entropy distribution of the gas (Voit & Bryan 2001 and Voit et al. 2002 also noted the possibility that feedback could truncate the entropy distribution, by removing the lowest entropy gas).”
What Shapes the Luminosity Function of Galaxies? (2003, background): “While the key physics of gas cooling and merging is now thought to be modeled with reasonable accuracy (Benson et al. 2001, 2002; Yoshida et al. 2002; Helly et al. 2003; Voit et al. 2002), other physics crucial to establishing the shape of the luminosity function remains poorly understood.”
The structural and scaling properties of nearby galaxy clusters. II. The M-T relation (2005, methodology): “This is in good agreement with the observed value; however, in this case the larger slope is mostly due to the variation of the concentration of the Dark Matter with mass in their model (Voit et al. 2002), which is larger than we observe (Paper I).”
Fossil H ii regions: self-limiting star formation at high redshift (2003, methodology): “The models we construct are in the spirit of Voit et al (2002); Tozzi & Norman (2001); Oh & Benson (2003); Babul et al (2002), which match observations of low-redshift cluster X-ray profiles well.”
X-ray coronae in simulations of disc galaxy formation (2010, background): “Cooling acts to reduce the gas temperature by selectively removing the lowest entropy gas and locking it into stars, thus raising the mean entropy of the remaining coronal gas (e.g. Voit et al. 2002).”
MASSIVE HALOS IN MILLENNIUM GAS SIMULATIONS: MULTIVARIATE SCALING RELATIONS (2009, methodology): “In the PH case, one expects the entropy floor to introduce curvature into the scaling relations (Voit et al. 2002), and so we extend this model to a quadratic with respect to µ for the ICM mass fraction and related measures for this case.”
Planck intermediate results: V. Pressure profiles of galaxy clusters from the Sunyaev-Zeldovich effect (2012, unknown): “In the cluster surroundings, accretion along ﬁlaments is three-dimensional and non-spherical (Tozzi & Norman 2001) and the initial conditions of the accretion shock are driven by the thermodynamical state of the (pre-shocked) in-falling material (Voit et al. 2002, 2003).”
Scaling laws in X-ray galaxy clusters at redshift between 0.4 and 1.3 (2003, background): “…are currently interpreted as evidence for non-gravitational processes, such as extra heating and radiative cooling, that affect the assembly of the baryons in the cluster potential well (e.g. Cavaliere et al. 1999; Bower et al. 2001; Tozzi & Norman 2001; Babul et al. 2002; Voit et al. 2002).”
A comparison of weak-lensing masses and X-ray properties of galaxy clusters (2007, background): “The net result is a increased temperature, or lower normalization (e.g. Voit et al. 2002; Borgani et al. 2004).”
Gas entropy in a representative sample of nearby X-ray galaxy clusters (REXCESS): relationship to gas mass fraction (2009, methodology): “1 (Tozzi & Norman 2001; Borgani et al. 2005; Voit et al. 2002, 2005; Mitchell et al. 2009).”
An Entropy Threshold for Strong Hα and Radio Emission in the Cores of Galaxy Clusters (2008, background): “…observational work (see Donahue et al. 2005, 2006; Cavagnolo et al. 2008a), we have focused on ICM entropy as a means for understanding the cooling and heating processes in clusters because it is a more fundamental property of the ICM than temperature or density alone (Voit et al. 2002; Voit 2005).”
INTRACLUSTER MEDIUM ENTROPY PROFILES FOR A CHANDRA ARCHIVAL SAMPLE OF GALAXY CLUSTERS (2009, methodology): “…it was realized that nongravitational effects, such as heating and radiative cooling in cluster cores, could not be neglected if models were to accurately replicate the process of cluster formation (e.g., Kaiser 1991; Evrard & Henry 1991; Loewenstein 2000; Voit et al. 2002; Borgani et al. 2002).”
On the Origin of Intracluster Entropy (2003, methodology): “From this point of view, simply adding a constant value to the entropy profile produced without preheating, as in the shifted models of Voit et al. (2002), seems like a good representation of the effects of preheating.”
Hydrodynamical simulations of cluster formation with central AGN heating (2005, background): “…invoked some sort of nongravitational heating to explain the cluster scaling relations (e.g. Kaiser 1991; Navarro, Frenk & White 1995; Bower 1997; Tozzi & Norman 2001; Voit & Bryan 2001; Borgani et al. 2001, 2004; Babul et al. 2002; Voit et al. 2002, 2003; Oh & Benson 2003; Tornatore et al. 2003).”
Near-Infrared Properties of Galaxy Clusters: Luminosity as a Binding Mass Predictor and the State of Cluster Baryons (2003, background): “The gas that cools to form stars is the lowest entropy gas, and its removal from the cluster causes similar structural signatures to those produced in the preheating scenario (see also Voit et al. 2002; Muanwong et al. 2002; Nath 2002).”
X‐ray properties of galaxy clusters and groups from a cosmological hydrodynamical simulation (2003, background): “Gas entropy is currently receiving considerable attention as a diagnostic tool for tracing the past dynamical and thermal history of the ICM (e.g., Bower 1997; Ponman et al. 1999; Tozzi & Norman 2001; Balogh et al. 2001; Borgani et al. 2001; Voit et al. 2002; Babul et al. 2002).”
The Birmingham-CfA cluster scaling project - III. Entropy and similarity in galaxy systems (2003, background): “In the case of the M :T relation, Lloyd-Davies et al. (2002) and Voit et al. (2002) show that systematic variations in the concentration parameter of dark matter haloes with mass, may play a key role in steepening its slope, as discussed in Paper I.”