相关论文: AGN and Cooling Flows
We investigate the transition of a radiatively inefficient phase of a viscous two temperature accreting flow to a cooling dominated phase and vice versa around black holes. Based on a global sub-Keplerian accretion disc model in steady…
The assumption that radiative cooling of gas in the centers of galaxy clusters is approximately balanced by energy input from a central supermassive black hole implies that the observed X-ray luminosity of the cooling flow region sets a…
It is now widely accepted that heating processes play a fundamental role in galaxy clusters, struggling in an intricate but fascinating `dance' with its antagonist, radiative cooling. Last generation observations, especially X-ray, are…
Recent observations show that the cooling flows in the central regions of galaxy clusters are highly suppressed. Observed AGN-induced cavities/bubbles are a leading candidate for suppressing cooling, usually via some form of mechanical…
Radiatively inefficient, hot accretion flows are widely considered as a relevant accretion mode in low-luminosity AGNs. We study spectral formation in such flows using a refined model with a fully general relativistic description of both…
The cooling flow problem is one of the central problems in galaxy clusters, and active galactic nucleus (AGN) feedback is considered to play a key role in offsetting cooling. However, how AGN jets heat and suppress cooling flows remains…
We study the heating of the cool cores in galaxy clusters by cosmic-rays (CRs) accelerated by the central active galactic nuclei (AGNs). We especially focus on the stability of the heating. The CRs stream with Alfv\'en waves in the…
Analyses of Chandra's first images of cooling flow clusters find smaller cooling rates than previously thought. Cooling may be occurring preferentially near regions of star formation in central cluster galaxies, where the local cooling and…
Although soft X-ray absorption features in AGN were discovered almost ten years ago, the nature and location of the gas creating them has remained controversial. Guided by the results of recent high-resolution X-ray spectroscopy, we argue…
AGN heating, through massive subrelativistic outflows, might be the key to solve the long-lasting `cooling flow problem' in cosmological systems. In a previous paper, we showed that cold accretion feedback and, to a lesser degree, Bondi…
The co-evolution between supermassive black holes and their environment is most directly traced by the hot atmospheres of dark matter halos. Cooling of the hot atmosphere supplies the central regions with fresh gas, igniting active galactic…
I study non-radiative cooling of X-ray emitting gas via heat conduction along magnetic field lines inside magnetic flux loops in cooling flow clusters of galaxies. I find that such heat conduction can reduce the fraction of energy radiated…
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…
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…
Recent observations have found extended multi-phase gas in a significant fraction of massive elliptical galaxies. We perform high-resolution three-dimensional hydrodynamical simulations of two idealized elliptical galaxies -- one…
We examine the effects of cooling flows on the T_X-L_Bol relation for a sample of the most X-ray luminous (L_Bol > 10^45 erg/s) clusters of galaxies known. Using high-quality ASCA X-ray spectra and ROSAT images we explicitly account for the…
When cool clouds are ram-pressure accelerated by a hot supersonic galactic wind, some of the clouds may be shredded by hydrodynamical instabilities and incorporated into the hot flow. Recent one-dimensional steady-state calculations show…
Precipitation of cold gas due to thermal instability in both galaxy clusters and the circumgalactic medium may regulate AGN feedback. We investigate thermal instability in idealized simulations of the circumgalactic medium with a parameter…
We study the effect of active galactic nuclei (AGN) heating on the chemodynamical evolution of elliptical galaxies and their X-ray and optical properties using high-resolution Lambda-dominated cold dark matter cosmological simulations. Our…
I discuss the multiphase nature of the intracluster medium whose neglect can lead to overestimates of the baryon fraction of clusters by up to a factor of two. The multiphase form of the cooling flow equations are derived and reduced to a…