ROSAT PSPC observations of 36 high-luminosity clusters of galaxies: constraints on the gas fraction

Ettori, S.; Fabian, A. C.

doi:10.1046/j.1365-8711.1999.02460.x

Cited by 190 publications

(262 citation statements)

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“…Our results indicate that the dark matter density falls as r −6 whereas the gas density falls as r −2 and thus the gas mass fraction increases rapidly at large radii. At r 500 our gas mass fraction value (see Table 2) is consistent with those for A2256 (Markevitch & Vikhlinin 1997), A401 (Nevalainen et al 1999), A2199 and A496 ) and for samples in Ettori & Fabian (1999) and Mohr et al (1999). At the virial radius we obtain f gas (≤ r 178 ) = 0.26 +0.05 −0.10 h −3/2 50 .…”

Section: Resultssupporting

confidence: 83%

Temperature and total mass profiles of the A3571 cluster of galaxies

Nevalainen

Kaastra

Parmar

et al. 2001

A&A

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Abstract. We present BeppoSAX results of a spatially resolved spectral analysis of A3571, a relaxed nearby cluster of galaxies. In the central 2 (130 h −1 50 kpc) radius the metal abundance is 0.49 ± 0.08 solar and the absorption (1.13 ± 0.28) 10 21 atom cm −2 , whereas elsewhere within an 8 (520 h −1 50 kpc) radius the abundance is 0.32 ± 0.05 solar and the absorption consistent with the galactic value of 4.4 10 20 atom cm −2 . The significant central metal abundance enhancement is consistent with the supernova enrichment scenario. The excess absorption may be attributed to the cooling flow, whose mass flow rate is 80 ± 40 M yr −1 from our spectral fit. The BeppoSAX and ASCA radial temperature profiles agree over the entire overlapping radial range r < 25 = 1.6 h −1 50 Mpc. The combined BeppoSAX and ASCA temperature profile exhibits a constant value out to a radius of ∼10 (650 h −1 50 kpc) and a significant decrease (T ∝ r −0.55 , corresponding to γ = 1.28) at larger radii. These temperature data are used to derive the total mass profile. The best fit NFW dark matter density model results in a temperature profile that is not convectively stable, but the model is acceptable within the uncertainties of the data. The temperature profile is acceptably modeled with a "core" model for the dark matter density, consisting of a core radius with a constant slope at larger radii. With this model the total mass and formal 90% confidence errors within the virial radius r178 (2.5 h −1 50 Mpc) are 9.1 +3.6 −1.5 10 14 h −1 50 M , by a factor of 1.4 smaller than the isothermal value. The gas mass fraction increases with radius, reaching f gas (r178) = 0.26 +0.05 −0.10 × h −3/2 50. Assuming that the measured gas mass fraction is the lower limit to the primordial baryonic fraction gives Ωm < 0.4 at 90% confidence.

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Section: Resultssupporting

confidence: 83%

Temperature and total mass profiles of the A3571 cluster of galaxies

Nevalainen

Kaastra

Parmar

et al. 2001

A&A

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“…On the observational side, the density profiles in this radial range are well-fitted by the β-model (see Eq. (4)), and several independent works converge to the canonical value of β ∼ 0.7 (e.g., Mohr et al 1999;Ettori & Fabian 1999;Vikhlinin et al 1999;Croston et al 2008;Ettori & Balestra 2009;Eckert et al 2011b). As a benchmark, we computed the values of β for our average density profile and the various sets of simulations, fixing the core radius to 0.12r 200 (e.g., Mohr et al 1999).…”

Section: Comparison Of Gas Density Profilesmentioning

confidence: 99%

The gas distribution in the outer regions of galaxy clusters

Eckert

Vazza

Ettori

et al. 2012

A&A

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Aims. We present our analysis of a local (z = 0.04−0.2) sample of 31 galaxy clusters with the aim of measuring the density of the X-ray emitting gas in cluster outskirts. We compare our results with numerical simulations to set constraints on the azimuthal symmetry and gas clumping in the outer regions of galaxy clusters. Methods. We have exploited the large field-of-view and low instrumental background of ROSAT/PSPC to trace the density of the intracluster gas out to the virial radius. We stacked the density profiles to detect a signal beyond r 200 and measured the typical density and scatter in cluster outskirts. We also computed the azimuthal scatter of the profiles with respect to the mean value to look for deviations from spherical symmetry. Finally, we compared our average density and scatter profiles with the results of numerical simulations. Results. As opposed to some recent Suzaku results, and confirming previous evidence from ROSAT and Chandra, we observe a steepening of the density profiles beyond ∼r 500 . Comparing our density profiles with simulations, we find that bibradiative runs predict density profiles that are too steep, whereas runs including additional physics and/or treating gas clumping agree better with the observed gas distribution. We report high-confidence detection of a systematic difference between cool-core and non cool-core clusters beyond ∼0.3r 200 , which we explain by a different distribution of the gas in the two classes. Beyond ∼r 500 , galaxy clusters deviate significantly from spherical symmetry, with only small differences between relaxed and disturbed systems. We find good agreement between the observed and predicted scatter profiles, but only when the 1% densest clumps are filtered out in the ENZO simulations. Conclusions. Comparing our results with numerical simulations, we find that bibradiative simulations fail to reproduce the gas distribution, even well outside cluster cores. Although their general behavior agrees more closely with the observations, simulations including cooling and star formation convert a large amount of gas into stars, which results in a low gas fraction with respect to the observations. Consequently, a detailed treatment of gas cooling, star formation, AGN feedback, and consideration of gas clumping is required to construct realistic models of the outer regions of clusters.

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“…Blue, green and red symbols refer to redshifts z = 0, 0.7 and 1 (from Ettori et al 2006). The shaded area indicates the range of values of the observed gas fraction (Ettori and Fabian 1999) include the effects of cooling, star formation and feedback heating, it is not clear whether they provide a reliable description of the gas distribution within real clusters. Kravtsov et al (2005) used high resolution simulations, based on an Eulerian code, for a set of clusters using both non-radiative and radiative physics.…”

Section: The Gas Mass Fractionmentioning

confidence: 99%

Thermodynamical Properties of the ICM from Hydrodynamical Simulations

et al. 2008

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Modern hydrodynamical simulations offer nowadays a powerful means to trace the evolution of the X-ray properties of the intra-cluster medium (ICM) during the cosmological history of the hierarchical build up of galaxy clusters. In this paper we review the current status of these simulations and how their predictions fare in reproducing the most recent X-ray observations of clusters. After briefly discussing the shortcomings of the self-similar model, based on assuming that gravity only drives the evolution of the ICM, we discuss how the processes of gas cooling and non-gravitational heating are expected to bring model predictions into better agreement with observational data. We then present results from the hydrodynamical simulations, performed by different groups, and how they compare with observational data. As terms of comparison, we use X-ray scaling relations between mass, luminosity, temperature and pressure, as well as the profiles of temperature and entropy. The results of this comparison can be summarised as follows: (a) which include gas cooling, star formation and supernova feedback, are generally successful in reproducing the X-ray properties of the ICM outside the core regions; (b) simulations generally fail in reproducing the observed "cool core" structure, in that they have serious difficulties in regulating overcooling, thereby producing steep negative central temperature profiles. This discrepancy calls for the need of introducing other physical processes, such as energy feedback from active galactic nuclei, which should compensate the radiative losses of the gas with high density, low entropy and short cooling time, which is observed to reside in the innermost regions of galaxy clusters.

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ROSAT PSPC observations of 36 high-luminosity clusters of galaxies: constraints on the gas fraction

Cited by 190 publications

References 59 publications

Temperature and total mass profiles of the A3571 cluster of galaxies

Temperature and total mass profiles of the A3571 cluster of galaxies

The gas distribution in the outer regions of galaxy clusters

Thermodynamical Properties of the ICM from Hydrodynamical Simulations

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