Thermal evaporation of gas from x-ray clusters

Loeb, Abraham

doi:10.1088/1475-7516/2007/03/001

Cited by 9 publications

(6 citation statements)

References 49 publications

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“…The other sources of non-thermal pressure support in outskirts of the cluster (turbulence, magnetic field, and cosmic rays) would reduce the thermal SZ effect relative to the expectation, if these effects are not taken into account in modeling the intracluster medium. Heat conduction may also play some role in suppressing the gas pressure (Loeb 2002(Loeb , 2007.…”

Section: Discussionmentioning

confidence: 99%

SEVEN-YEARWILKINSON MICROWAVE ANISOTROPY PROBE(WMAP) OBSERVATIONS: COSMOLOGICAL INTERPRETATION

Komatsu¹,

Smith²,

Dunkley³

et al. 2011

ApJS

7,552

471

6,407

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The combination of seven-year data from WMAP and improved astrophysical data rigorously tests the standard cosmological model and places new constraints on its basic parameters and extensions. By combining the WMAP data with the latest distance measurements from the baryon acoustic oscillations (BAO) in the distribution of galaxies and the Hubble constant (H 0 ) measurement, we determine the parameters of the simplest six-parameter ΛCDM model. The power-law index of the primordial power spectrum is n s = 0.968 ± 0.012 (68% CL) for this data combination, a measurement that excludes the Harrison-Zel'dovich-Peebles spectrum by 99.5% CL. The other parameters, including those beyond the minimal set, are also consistent with, and improved from, the five-year results. We find no convincing deviations from the minimal model. The seven-year temperature power spectrum gives a better determination of the third acoustic peak, which results in a better determination of the redshift of the matter-radiation equality epoch. Notable examples of improved parameters are the total mass of neutrinos, m ν < 0.58 eV (95% CL), and the effective number of neutrino species, N eff = 4.34 +0.86 −0.88 (68% CL), which benefit from better determinations of the third peak and H 0 . The limit on a constant dark energy equation of state parameter from WMAP+BAO+H 0 , without high-redshift Type Ia supernovae, is w = −1.10 ± 0.14 (68% CL). We detect the effect of primordial helium on the temperature power spectrum and provide a new test of big bang nucleosynthesis by measuring Y p = 0.326 ± 0.075 (68% CL). We detect, and show on the map for the first time, the tangential and radial polarization patterns around hot and cold spots of temperature fluctuations, an important test of physical processes at z = 1090 and the dominance of adiabatic scalar fluctuations. The seven-year polarization data have significantly improved: we now detect the temperature-E-mode polarization cross power spectrum at 21σ , compared with 13σ from the five-year data. With the seven-year temperature-B-mode cross power spectrum, the limit on a rotation of the polarization plane due to potential parity-violating effects has improved by 38% to Δα = −1.• 1 ± 1.• 4(statistical) ± 1.• 5(systematic) (68% CL). We report significant detections of the Sunyaev-Zel'dovich (SZ) effect at the locations of known clusters of galaxies. The measured SZ signal agrees well with the expected signal from the X-ray data on a cluster-by-cluster basis. However, it is a factor of 0.5-0.7 times the predictions from "universal profile" of Arnaud et al., analytical models, and hydrodynamical simulations. We find, for the first time in the SZ effect, a significant difference between the cooling-flow and non-cooling-flow clusters (or relaxed and non-relaxed clusters), which can explain some of the discrepancy. This lower amplitude is consistent with the lower-than-theoretically expected SZ power spectrum recently measured by the South Pole Telescope Collaboration.

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Section: Discussionmentioning

confidence: 99%

SEVEN-YEARWILKINSON MICROWAVE ANISOTROPY PROBE(WMAP) OBSERVATIONS: COSMOLOGICAL INTERPRETATION

Komatsu¹,

Smith²,

Dunkley³

et al. 2011

ApJS

7,552

471

6,407

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“…This piece of observational evidence has motivated proposals for thermal evaporation of galaxy clusters, such as the work by Loeb (2007). This work supposes that the outer portions of galaxy clusters could thermally evaporate, losing up to 10% of their mass.…”

Section: Thermal Evaporation and Missing Baryonsmentioning

confidence: 99%

The Magnetothermal Instability in the Intracluster Medium

Parrish

Stone

Lemaster

2008

Astrophysical Journal

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The electron mean free path in the intracluster medium (ICM) of galaxy clusters is much larger than the gyroradius; thus, heat is transported anisotropically along magnetic field lines. We show that the intracluster medium is unstable to the magnetothermal instability (MTI ) where the temperature declines with radius using MHD simulations with anisotropic thermal conduction. As a result of the MTI, we find that the temperature profile of the ICM can be substantially modified on timescales of several billion years, while the magnetic field is amplified by dynamo action up to more than 50 times the original energy. We also show that the instability drives field lines to become preferentially radial, leading to conduction that is a highly efficient fraction of the Spitzer conductivity.

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“…For example, the thermodynamic state of the shocked gas, as well as the shock position, depends on the pre-shock gas temperature; the shock will be weaker if the infalling gas is pre-heated (Tozzi et al 2000). Even worse, recently it was noted that the non-fluid properties may be important in regions near the virial radius, where the Coulomb collisional mean free path is comparable to the cluster size of a few Mpc (Loeb 2007). The Coulomb collisional timescale can also be of the order of the age of the cluster.…”

Section: Introductionmentioning

confidence: 99%

“…This suggests that a full kinetic gas theory is needed instead of the fluid approximation when studying the gas properties near the edge of the cluster. Direct consequences include non-equipartition between electrons and ions (Fox & Loeb 1997;Ettori & Fabian 1998), element sedimentation (Chuzhoy & Loeb 2004), and suprathermal evaporation of hot gas from the clusters (Loeb 2007; see also Medvedev 2007). Some of these effects can lead to a bias in baryon fraction measurements, and hence cosmological studies.…”

Section: Introductionmentioning

confidence: 99%

Effects of the Non-Equipartition of Electrons and Ions in the Outskirts of Relaxed Galaxy Clusters

Wong

Sarazin

2009

ApJ

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We have studied the effects of electron-ion non-equipartition in the outer regions of relaxed clusters for a wide range of masses in the ΛCDM cosmology using one-dimensional hydrodynamic simulations. The effects of the non-adiabatic electron heating efficiency, β, on the degree of non-equipartition are also studied. Using the gas fraction f gas = 0.17 (which is the upper limit for a cluster), we give a conservative lower limit of the non-equipartition effect on clusters. We have shown that for a cluster with a mass of M vir ∼ 1.2 × 10 15 M ⊙ , electron and ion temperatures differ by less than a percent within the virial radius R vir . The difference is ≈ 20% for a non-adiabatic electron heating efficiency of β ∼ 1/1800 to 0.5 at ∼ 1.4R vir . Beyond that radius, the non-equipartition effect depends rather strongly on β, and such a strong dependence at the shock radius can be used to distinguish shock heating models or constrain the shock heating efficiency of electrons. With our simulations, we have also studied systematically the signatures of non-equipartition on X-ray and Sunyaev-Zel'dovich (SZ) observables. We have calculated the effect of non-equipartition on the projected temperature and X-ray surface brightness profiles using the MEKAL emission model. We found that the effect on the projected temperature profiles is larger than that on the deprojected (or physical) temperature profiles. The non-equipartition effect can introduce a ∼ 10% bias in the projected temperature at R vir for a wide range of β. We also found that the effect of non-equipartition on the projected temperature profiles can be enhanced by increasing metallicity. In the low-energy band 1 keV, the non-equipartition model surface brightness can be higher than that of the equipartition model in the cluster outer regions. Future X-ray observations extending to ∼ R vir or even close to the shock radius should be able to detect these non-equipartition signatures. For a given cluster, the difference between the SZ temperature decrements for the equipartition and the non-equipartition models, δ∆T SZE , is larger at a higher redshift. For the most massive clusters at z ≈ 2, the differences can be δ∆T SZE ≈ 4-5 µK near the shock radius. We also found that for our model in the ΛCDM universe, the integrated SZ bias, Y non-eq /Y eq , evolves slightly (at a percentage level) with redshift, which is in contrast to the self-similar model in the Einstein-de Sitter universe. This may introduce biases in cosmological studies using the f gas technique. We discussed briefly whether the equipartition and non-equipartition models near the shock region can be distinguished by future radio observations with, for example, the Atacama Large Millimeter Array. Subject headings: cosmic microwave background -galaxies: clusters: general -hydrodynamicsintergalactic medium -shock waves -X-rays: galaxies: clusters 1 R ∆ is the radius within which the mean total mass density of the cluster is ∆ times the critical density. The virial radius R vir is defined as a radius within...

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Thermal evaporation of gas from x-ray clusters

Cited by 9 publications

References 49 publications

SEVEN-YEARWILKINSON MICROWAVE ANISOTROPY PROBE(WMAP) OBSERVATIONS: COSMOLOGICAL INTERPRETATION

SEVEN-YEARWILKINSON MICROWAVE ANISOTROPY PROBE(WMAP) OBSERVATIONS: COSMOLOGICAL INTERPRETATION

The Magnetothermal Instability in the Intracluster Medium

Effects of the Non-Equipartition of Electrons and Ions in the Outskirts of Relaxed Galaxy Clusters

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