The Effects of Radiative Cooling on the Entropy Distribution of Intracluster Gas
نویسندگان
چکیده
High resolution X-ray observations indicate that the entropy profiles in the central regions of some massive cooling flow clusters are well approximated by powerlaws. McCarthy and coworkers recently accounted for this trend with an analytic model that includes the detailed effects of radiative cooling. Interestingly, these authors found that cooling (and subsequent inflow of the gas) naturally establishes approximate steady-state powerlaw entropy profiles in the cores of clusters. However, the origin of this behavior and its dependence on initial conditions have yet to be elucidated. In the present study, we explain this trend in the context of the self-similar cooling wave model developed previously by Bertschinger (1989). It is shown that the logarithmic slope of the entropy profile in the cores of relaxed cooling flow clusters is given by a simple analytic function that depends only on the logarithmic slopes of the local gravitational potential and the cooling function. We discuss a number of potentially interesting uses of the above result, including: (1) a way of measuring the shapes of gravitational potentials of cooling flow clusters (which may, for example, be compared against the standard hydrostatic equilibrium method); (2) a simple method for constructing realistic analytic cluster models that include the effects of radiative cooling; and (3) a test of the reliability of cooling routines implemented in analytic models and hydrodynamic simulations. Subject headings: cosmology: theory — galaxies: clusters: general — X-rays: galaxies: clusters
منابع مشابه
Modified-entropy Models for the Intracluster Medium
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-ma...
متن کاملOn the Origin of Intracluster Entropy
The entropy distribution of the intracluster medium and the shape of its confining potential well completely determine the X-ray properties of a relaxed cluster of galaxies, motivating us to explore the origin of intracluster entropy and to describe how it develops in terms of some simple models. We present an analytical model for smooth accretion, including both preheating and radiative coolin...
متن کاملThe entropy distribution in clusters: evidence of feedback?
The entropy of the intracluster medium at large radii has been shown recently to deviate from the self-similar scaling with temperature. Using N -body/hydrodynamic simulations of the ΛCDM cosmology, we demonstrate that this deviation is evidence that feedback processes are important in generating excess entropy in clusters. While radiative cooling increases the entropy of intracluster gas, resu...
متن کاملThe Effect of Radiative Cooling on the Sunyaev-Zel’dovich Cluster Counts and Angular Power Spectrum: Analytic Treatment
Recently, the entropy excess detected in the central cores of groups and clusters has been successfully interpreted as being due to radiative cooling of the hot intragroup/intracluster gas. In such a scenario, the entropy floors Sfloor in groups/clusters at any given redshift are completely determined by the conservation of energy. In combination with the equation of hydrostatic equilibrium and...
متن کاملCooling flows and the entropy of the intragroup medium
We study steady, homogeneous and subsonic cooling flows in poor clusters of galaxies in light of the recent proposal that radiative cooling of the intracluster gas can explain the observations of the ‘entropy floor’ and other related X-ray observations. We study a family of cooling flow solutions parameterized by the mass flux rate, and then determine the resulting entropy and the X-ray luminos...
متن کامل