相关论文: Heating Cooling Flows with Weak Shock Waves
Room temperature compressed air was pumped into a short (H/D = 0.18) vortex chamber. Experiments revealed temperature separation. The highest temperature of the periphery was 465 degC, and the lowest temperature of the central zone was -45…
We describe 2D gasdynamical models of jets that carry mass as well as energy to the hot gas in galaxy clusters. These flows have many attractive attributes for solving the galaxy cluster cooling flow problem: Why the hot gas temperature and…
Galaxy cluster cores are pervaded by hot gas which radiates at far too high a rate to maintain any semblance of a steady state; this is referred to as the cooling flow problem. Of the many heating mechanisms that have been proposed to…
We evaluate whether dissipation of turbulence injected into hot cluster atmospheres by jets and bubbles can offset radiative cooling flows. No trends are found between atmospheric velocity dispersion, $\sigma_v$, and either the ratio of…
The discrepancy between expected and observed cooling rates of X-ray emitting gas has led to the {\it cooling flow problem} at the cores of clusters of galaxies. A variety of models have been proposed to model the observed X-ray spectra and…
Active galactic nuclei are clearly heating gas in `cooling flows'. The effectiveness and spatial distribution of the heating are controversial. We use three-dimensional simulations on adaptive grids to study the impact on a cooling flow of…
Feedback from active galactic nuclei (AGN) is believed to be the most promising solution to the cooling flow problem in cool-core clusters, though how exactly the jet energy is transformed into heat is a subject of debate. Dissipation of…
We present a spectral analysis of cool and cooling gas in 45 cool-core clusters and groups of galaxies obtained from Reflection Grating Spectrometer (RGS) XMM-$Newton$ observations. The high-resolution spectra show FeXVII emission in many…
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 (RGS) on…
We present three-dimensional simulations of viscous dissipation of AGN induced gas motions and waves in clusters of galaxies. These simulations are motivated by recent detections of ripples in the Perseus and Virgo clusters. Although the…
Galactic winds are crucial to the cosmic cycle of matter, transporting material out of the dense regions of galaxies. Observations show the coexistence of different temperature phases in such winds, which is not easy to explain. We present…
We investigate a model of galaxy clusters in which the hot intracluster gas is efficiently heated by dynamical friction (DF) of galaxies. We allow for both subsonic and supersonic motions of galaxies and use the gravitational drag formula…
High resolution X-ray spectroscopy of the hot gas in galaxy clusters has shown that the gas is not cooling to low temperatures at the predicted rates of hundreds to thousands of solar masses per year. X-ray images have revealed giant…
In many clusters of galaxies there is evidence for cooling flows in the central regions. The ultimate fate of the gas which cools is still unknown. A possibility is that a fraction of the gas forms cold molecular clouds. We investigate the…
During the last few decades, the most widely favored models for coronal heating have involved the in situ dissipation of energy, with footpoint shuffling giving rise to multiple current sheets (the "nanoflare" model) or to Alfv{\'e}n waves…
There is mounting observational evidence from Chandra for strong interaction between keV gas and AGN in cooling flows. It is now widely accepted that the temperatures of cluster cores are maintained at a level of 1 keV and that the mass…
Observations of gravitational lensing indicate that the mass distribution in clusters of galaxies (where most of the mass is dark matter) is highly peaked towards the center, while X-ray observations imply that the gas is more extended. The…
By simulating jet-inflated bubbles in cooling flows with the PLUTO hydrodynamic code we show that mixing of high entropy shocked jet's material with the intra-cluster medium (ICM) is the major heating process perpendicular to the jets'…
Protoplanetary disks are mainly heated by radiation from the central star. Since the incident stellar flux at any radius is sensitive to the disk structure near that location, an unstable feedback may be present. Previous investigations…
The hot, X-ray-emitting intracluster medium (ICM) is the dominant baryonic constituent of clusters of galaxies. In the cores of many clusters, radiative energy losses from the ICM occur on timescales significantly shorter than the age of…