Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userA note on Temperature Profiles of rich Clusters of Galaxies
112
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We derive here the mean temperature profile for a sample of hot, medium distant clusters recently observed with XMM-Newton, whose profiles are available from the literature, and compare it with the mean temperature profile found from BeppoSAX data. The XMM-Newton and BeppoSAX profiles are in good agreement between 0.05 and 0.25 r_180. From 0.25 to about 0.5 r_180 both profiles decline, however the BeppoSAX profile does so much more rapidly than the XMM-Newton profile.
rate research
Read More
We report results from the analysis of 21 nearby galaxy clusters, 11 with cooling flow (CF) and 10 without cooling flow, observed with BeppoSAX. The temperature profiles of both CF and non-CF systems are characterized by an isothermal core extending out to 0.2 r_180; beyond this radius both CF and non-CF cluster profiles rapidly decline. Our results differ from those derived by other authors who either found continuously declining profiles or substantially flat profiles. Neither the CF nor the non-CF profiles can be modeled by a polytropic temperature profile, the reason being that the radius at which the profiles break is much larger than the core radius characterizing the gas density profiles. For r > 0.2 r_180, where the gas can be treated as a polytrope, the polytropic indices derived for CF and non-CF systems are respectively 1.20 +/- 0.06 and 1.46 +/- 0.06. The former index is closer to the isothermal value, 1, and the latter to the adiabatic value, 5/3. Published hydrodynamic simulations do not reproduce the peculiar shape of the observed temperature profile, probably suggesting that a fundamental ingredient is missing.
We use the Evolution and assembly of galaxies and their environments (EAGLE) cosmological simulation to investigate the effect of baryons on the density profiles of rich galaxy clusters. We focus on EAGLE clusters with $M_{200}>10^{14}~M_odot$ of which we have six examples. The central brightest cluster galaxies (BCGs) in the simulation have steep stellar density profiles, $rho_*(r) propto r^{-3}$. Stars dominate the mass density for $r<10~rm{kpc}$, and, as a result, the total mass density profiles are steeper than the Navarro-Frenk-White (NFW) profile, in remarkable agreement with observations. The dark matter halo itself closely follows the NFW form at all resolved radii ($rgtrsim3.0~rm{kpc}$). The EAGLE BCGs have similar surface brightness and line-of-sight velocity dispersion profiles as the BCGs in the sample of Newman et al., which have the most detailed measurements currently available. After subtracting the contribution of the stars to the central density, Newman et al. infer significantly shallower slopes than the NFW value, in contradiction with the EAGLE results. We discuss possible reasons for this discrepancy, and conclude that an inconsistency between the kinematical model adopted by Newman et al. for their BCGs, which assumes isotropic stellar orbits, and the kinematical structure of the EAGLE BCGs, in which the orbital stellar anisotropy varies with radius and tends to be radially biased, could explain at least part of the discrepancy.
The results of hydrodynamic simulations of the Virgo and Perseus clusters suggest that thermal conduction is not responsible for the observed temperature and density profiles. As a result it seems that thermal conduction occurs at a much lower level than the Spitzer value. Comparing cavity enthalpies to the radiative losses within the cooling radius for seven clusters suggests that some clusters are probably heated by sporadic, but extremely powerful, AGN outflows interspersed between more frequent but lower power outflows.
In this paper we study the iron content of a sample of 22 nearby hot clusters observed with BeppoSAX. We find that the global iron mass of clusters is tightly related to the cluster luminosity and that the relatively loose correlation between the iron mass and the cluster temperature follows from the combination of the iron mass vs. luminosity and luminosity vs. temperature correlations. The iron mass is found to scale linearly with the intracluster gas mass, implying that the global iron abundance in clusters is roughly constant. This result suggests that enrichment mechanisms operate at a similar rate in all clusters. By employing population synthesis and chemical enrichment models, we show that the iron mass associated to the abundance excess which is always found in the centre of cool core clusters can be entirely produced by the brightest cluster galaxy (BCG), which is always found at the centre of cool core clusters. The iron mass associated to the excess, the optical magnitude of the BCG and the temperature of the cluster are found to correlate with one another suggesting a link between the properties of the BCG and the hosting cluster. These observational facts lends strength to current formation theories which envisage a strong connection between the formation of the giant BCG and its hosting cluster.
We present Chandra gas temperature profiles at large radii for a sample of 13 nearby, relaxed galaxy clusters and groups, which includes A133, A262, A383, A478, A907, A1413, A1795, A1991, A2029, A2390, MKW4, RXJ1159+5531, and USGC S152. The sample covers a range of average temperatures from 1 to 10 keV. The clusters are selected from the archive or observed by us to have sufficient exposures and off-center area coverage to enable accurate background subtraction and reach the temperature accuracy of better than 20-30% at least to r=0.4-0.5 r_180, and for the three best clusters, to 0.6-0.7 r_180. For all clusters, we find cool gas in the cores, outside of which the temperature reaches a peak at r =~ 0.15 r_180 and then declines to ~0.5 of its peak value at r =~ 0.5 r_180. When the profiles are scaled by the cluster average temperature (excluding cool cores) and the estimated virial radius, they show large scatter at small radii, but remarkable similarity at r>0.1-0.2 r_180 for all but one cluster (A2390). Our results are in good agreement with previous measurements from ASCA by Markevitch et al. and from Beppo-SAX by DeGrandi & Molendi. Four clusters have recent XMM-Newton temperature profiles, two of which agree with our results, and we discuss reasons for disagreement for the other two. The overall shape of temperature profiles at large radii is reproduced in recent cosmological simulations.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
