Baryons at the Edge of the X-ray–Brightest Galaxy Cluster

Simionescu, A.; Allen, S. W.; Mantz, Adam; Werner, Norbert; Takei, Yoh; Morris, R. Glenn; Fabian, A. C.; Sanders, J. S.; Nulsen, P. E. J.; George, Matthew R.; Taylor, G. B.

doi:10.1126/science.1200331

Cited by 276 publications

(461 citation statements)

References 32 publications

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“…This would however not explain an offset between our results and other work that relies on Chandra data as well, like Sun et al (2009). Furthermore, other investigators have found the cluster density profiles to be consistent with (Humphrey et al 2011) or even flatter than predictions Simionescu et al 2011;Urban et al 2011).…”

Section: Discussioncontrasting

confidence: 52%

Testing the low-mass end of X-ray scaling relations with a sample ofChandragalaxy groups

Eckmiller

Hudson

Reiprich

2011

A&A

125

182

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Context. Well-determined scaling relations between X-ray observables and cluster mass are essential for using large cluster samples to constrain fundamental cosmological parameters. Scaling relations between cluster masses and observables, such as the luminositytemperature, mass-temperature, luminosity-mass relations, have been investigated extensively, however the question of whether these relations hold true also for poor clusters and groups remains unsettled. Some evidence supports a "break" at the low end of the group/cluster mass range, possibly caused by the stronger influence of non-gravitational physics on low-mass systems. Aims. The main goal of this work is to test local scaling relations for the low-mass range in order to check whether or not there is a systematic difference between clusters and groups, and to thereby extend this method of reliable and convenient cluster mass determination for future large samples down to the group regime. Methods. We compiled a statistically complete sample of 112 X-ray galaxy groups, 26 of which have usable Chandra data. Temperature, metallicity, and surface brightness profiles were created for these 26 groups, and used to determine the main physical quantities and scaling relations. We then compared the group properties to those of the HIFLUGCS clusters, as well as several other group and cluster samples. Results. We present radial profiles for the individual objects and scaling relations of the whole sample (. Temperature and metallicity profiles behave universally, except for the core regions.and L x − Y x relations of the group sample are generally in good agreement with clusters. The L x − T relation steepens for T < 3 keV, which could point to a larger impact of heating mechanisms on cooler systems. We found a significant drop in the gas mass fraction below < ∼ 1 keV, as well as a correlation with radius, which indicates the ICM is less dominant in groups compared to clusters and the galaxies have a stronger influence on the global properties of the system. In all relations the intrinsic scatter for groups is larger than for clusters, which appears not to be correlated with merger activity but could be due to scatter caused by baryonic physics in the group cores. We also demonstrate the importance of selection effects. Conclusions. We have found some evidence for a similarity break between groups and clusters. However this does not have a strong effect on the scaling relations.

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Section: Discussioncontrasting

confidence: 52%

Testing the low-mass end of X-ray scaling relations with a sample ofChandragalaxy groups

Eckmiller

Hudson

Reiprich

2011

A&A

125

182

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“…Collisional ionization and electron-ion equilibrium are likely to hold out to r200 in the Perseus Cluster, where the equilibration timescales are only ~3.5×10 8 yr and ~7.3×10 8 yr, respectively. Within a radius r ~ 400 kpc (~0.2r200; not shown here) metal enrichment is strongly influenced by the brightest cluster galaxy and the metallicity is centrally peaked 4,9 . Along the eastern direction, large scale sloshing motions are present and are uplifting the ICM from smaller radii out to r ~ 650 kpc 14 .…”

Section: Competing Interestsmentioning

confidence: 85%

A uniform metal distribution in the intergalactic medium of the Perseus cluster of galaxies

Werner

Urban

Simionescu

et al. 2013

Nature

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Most of the metals (elements heavier than helium) ever produced by stars in the member galaxies of galaxy clusters currently reside within the hot, X-ray emitting intra-cluster gas. Observations of X-ray line emission from this intergalactic medium have suggested a relatively small cluster-to-cluster scatter outside of the cluster centers 1,2 and enrichment with iron out to large radii 3,4,5 , leading to the idea that the metal enrichment occurred early in the history of the Universe 3 . Models with early enrichment predict a uniform metal distribution at large radii in clusters, while late-time enrichment, favored by some previous studies 6,7 , is expected to introduce significant spatial variations of the metallicity. To discriminate clearly between these competing models, it is essential to test for potential inhomogeneities by measuring the abundances out to large radii along multiple directions in clusters, which has not hitherto been done. Here we report a remarkably uniform measured iron abundance, as a function of radius and azimuth, that is statistically consistent with a constant value of ZFe = 0.306 ± 0.012 Solar out to the edge of the nearby Perseus Cluster. This homogeneous distribution requires that most of the metal enrichment of the intergalactic medium occurred before the cluster formed, likely over 10 billion years ago, during the period of maximal star formation and black hole activity.Between 2009 and 2011, we obtained a total of 84 observations of the Perseus Cluster with the Suzaku X-ray satellite, as a Key Project for that mission. The pointings covered eight azimuthal directions from the cluster center out to an offset angle of 2 o , with a total exposure time of over 1 million seconds. We have analyzed the data from all three functioning X-ray Imaging Spectrometers, extracting spectra from annuli centered on the cluster center. We modeled the spectra from each of the 76 independent regions as a single-temperature thermal plasma in collisional ionization equilibrium, with the temperature, iron abundance, and spectrum normalization included as free parameters 8 .The measured radial and azimuthal variation of the iron abundance of the hot intra-cluster medium (ICM) out to the edge of the Perseus Cluster along the eight different directions is presented in Fig. 1. We define this `edge' as r200, the radius within which the mean enclosed mass density of the cluster is 200 times the critical density of the Universe at the cluster redshift (for the Perseus Cluster r200 = 1.8 Mpc, corresponding to 82 arcmin 4 ). We have tested the statistical uniformity of the measured iron abundance at radii r > 400 kpc (i.e. beyond the central metallicity peak associated with the brightest cluster galaxy 4,9 ) by modeling the data from all radii and azimuths with a constant abundance. The measured chi-square value of 65.8 for 75 degrees of freedom is consistent with the null hypothesis of a constant iron abundance with a value of ZFe = 0.306±0.012 Solar (68% confidence limit; we adopt a Solar iron abundance of ...

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“…The long conduction timescale therefore delays the virialization of the stripped, low-entropy gas inside the potential well of the main cluster (De Grandi et al 2016;Eckert et al 2014), which causes the ICM in the outer regions of massive clusters to be clumpy (Mathiesen et al 1999;Nagai & Lau 2011;Vazza et al 2013). Since the X-ray emissivity depends on the squared gas density, inhomogeneities in the gas distribution lead to an overestimation of the mean gas density (Eckert et al 2015b;Nagai & Lau 2011;Simionescu et al 2011), which biases the measured entropy low. This effect needs to be taken into account when measuring the entropy associated with the bulk of the ICM.…”

Section: Introductionmentioning

confidence: 99%

The XMM cluster outskirts project (X‐COP)

et al. 2017

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Galaxy clusters are thought to grow hierarchically through the continuous merging and accretion of smaller structures across cosmic time. In the Local Universe, these phenomena are still active in the outer regions of massive clusters (R > R500), where the matter distribution is expected to become clumpy and asymmetric because of the presence of accreting structures. We present the XMM-Newton Cluster Outskirts Project (X-COP), which targets the outer regions of a sample of 13 massive clusters (M500 > 3 × 10 14 M ) in the redshift range 0.04-0.1 at uniform depth. The sample was selected based on the signal-to-noise ratio in the Planck Sunyaev-Zeldovich (SZ) survey with the aim of combining high-quality X-ray and SZ constraints throughout the entire cluster volume. Our observing strategy allows us to reach a sensitivity of 3 × 10 −16 ergs cm −2 s −1 arcmin −2 in the [0.5-2.0] keV range thanks to a good control of systematic uncertainties. The combination of depth and field of view achieved in X-COP will allow us to pursue the following main goals: i) measure the distribution of entropy and thermal energy to an unprecedented level of precision; ii) assess the presence of non-thermal pressure support in cluster outskirts; iii) study the occurrence and mass distribution of infalling gas clumps. We illustrate the capabilities of the program with a pilot study on the cluster Abell 2142.

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Baryons at the Edge of the X-ray–Brightest Galaxy Cluster

Cited by 276 publications

References 32 publications

Testing the low-mass end of X-ray scaling relations with a sample ofChandragalaxy groups

Testing the low-mass end of X-ray scaling relations with a sample ofChandragalaxy groups

A uniform metal distribution in the intergalactic medium of the Perseus cluster of galaxies

The XMM cluster outskirts project (X‐COP)

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