Outer Regions of the Cluster Gaseous Atmospheres

Vikhlinin, A.; Forman, W.; Jones, C.

doi:10.1086/307876

Cited by 187 publications

(248 citation statements)

References 45 publications

(59 reference statements)

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“…Vikhlinin et al (1999) recently found R ∝ T 0.57±0.04 , which is close to the predicted scaling law. Both the gas density and temperature profiles of hot clusters (T > 4 keV) do show regularity Neumann & Arnaud 1999, hereafter Paper I;Vikhlinin et al 1999). The shapes of various clusters, once the radius is scaled to the virial radius, look remarkably similar outside the cooling flow region, Send offprint requests to: D. M. Neumann, e-mail: ddon@cea.fr supporting the existence of an universal underlying dark matter profile.…”

Section: Introductionsupporting

confidence: 81%

Self-similarity of clusters of galaxies and the $L_{\sf X}{-} T$ relation

Neumann¹,

Arnaud²

2001

A&A

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Abstract. In this paper based on ROSAT/PSPC data we investigate the emission measure profiles of a sample of hot clusters of galaxies (kT > 3.5 keV) in order to explain the differences between observed and theoretically predicted LX-T relation. Looking at the form of the emission measure profiles as well as their normalizations we find clear indication that indeed the profiles have similar shapes once scaled to the virial radius, however, the normalization of the profiles shows a strong temperature dependence. We introduce a Mgas-T relation with the dependence Mgas ∝ T 1.94 . This relationship explains the observed LX-T relation and reduces the scatter in the scaled profiles by a factor of 2 when compared to the classical scaling. We interpret this finding as strong indication that the Mgas-T relation in clusters deviates from classical scaling.

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Section: Introductionsupporting

confidence: 81%

Self-similarity of clusters of galaxies and the $L_{\sf X}{-} T$ relation

Neumann¹,

Arnaud²

2001

A&A

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“…The β-model also overestimates the true profiles at r r c . They are steeper than the power-law behavior of the β-model (Vikhlinin et al 1999), as is also found in numerical simulations (e.g. Rasia et al 2004, online).…”

supporting

confidence: 70%

Theβ-model of the intracluster medium

Arnaud¹

2009

A&A

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The space between the galaxies in clusters of galaxies is filled with a hot tenous gas. Its high temperature (0.5-15 keV) is set by the the virialization process in the cluster's deep potential well, and the gas emits in X-rays predominantly through thermal Bremsstrahlung. This intracluster medium (ICM) is the main baryonic components of clusters and accounts for about 10% of the total dark matter dominated mass. While this is now wellestablished, it was not the case in the mid 70s, when the pioneering paper by Cavaliere & Fusco-Femiano (1976), which set the basis of the powerful β-model, was written.The idea of an ICM was proposed as early as 1959, but it took 10 years after its first detection in 1966 to definitively prove the existence of the hot ICM (see also Sarazin 1986; Biviano 2000, for a historical review). Limber (1959) stated that it is "rather likely that there is an appreciable quantity of intracluster gas pervading (...) clusters", primordial gas left over from galaxy formation, gas swept out of galaxies during galaxy collisions, or both. However, "it (was) not at all clear at (that) time whether one should expect the intracluster gas to be hot or cold". The first observational clue was the detection of M 87 in the Virgo cluster with the Geiger counters onboard an Aerobee rocket (Byram et al. 1966), which was also the first detection of an X-ray source associated with a cluster. The next major advance was made with Uhuru, the first satellite dedicated to X-ray astronomy, launched in 1970. Uhuru performed an all-sky X-ray survey and permitted longer observations of individual sources than with rockets experiments. This established that clusters are X-ray luminous sources and that the X-ray emission is extended and not time variable (e.g. Gursky et al. 1972, online).The detectors onboard Uhuru and rocket experiments were non-imaging proportional counters equipped with collimators to limit the field of view. Because of the crude spectral and spatial resolution (∼1 • ) of the detectors, the origin of the X-ray emission was ambiguous. Three possibilities were considered: 1) thermal bremsstrahlung from a hot tenuous gas; 2) inverse Compton (IC) scattering of CMB photons by relativistic electrons within the clusters; and 3) summed contributions of stellar sources (binaries or globular clusters). This was discussed very early by Felten et al. (1966) who correctly favored the thermal model on energetics arguments (unfortunately based on a spurious detection of the Coma cluster).In their paper, Cavaliere and Fusco-Femiano outlined several problems with the IC interpretation and, in particular, with the low value of the magnetic field implied by the ratio of the X-ray and Synchrotron radio luminosity. On the other hand, they emphasized that the IC emission is expected to stand out at energies above the thermal emission's exponential cut-off, E ∼ > 10 keV. The IC emission was indeed searched later on as an excess over the thermal emission in the hard X-ray band with Beppo-SAX, RXTE, and now Suzaku. Its level r...

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“…Interestingly, some of the Suzaku results indicate very steep temperature profiles and shallow density profiles in cluster outskirts, at variance with the results from XMM-Newton ; Leccardi & Molendi 2008;Snowden et al 2008;Croston et al 2008), Chandra (Vikhlinin et al 2006;Ettori & Balestra 2009), ROSAT (Vikhlinin et al 1999;Neumann 2005), and with the results from numerical simulations (Roncarelli et al 2006;Tozzi & Norman 2001;. Thus, the behavior of the gas in cluster outskirts is still the subject of debate.…”

Section: Introductionmentioning

confidence: 89%

The gas distribution in the outer regions of galaxy clusters

Eckert

Vazza

Ettori

et al. 2012

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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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Outer Regions of the Cluster Gaseous Atmospheres

Cited by 187 publications

References 45 publications

Self-similarity of clusters of galaxies and the $L_{\sf X}{-} T$ relation

Self-similarity of clusters of galaxies and the $L_{\sf X}{-} T$ relation

Theβ-model of the intracluster medium

The gas distribution in the outer regions of galaxy clusters

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