Nonthermal Origin of the EUV and Soft X-Rays from the Coma Cluster:Cosmic Rays in Equipartition with the Thermal Medium

Lieu, Richard; Ip, W. H.; Axford, W. I.; Bonamente, Massimiliano

doi:10.1086/311790

Cited by 69 publications

(85 citation statements)

References 19 publications

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“…Evidence of non-thermal electrons in the ICM exist in the form of synchrotron radio emission (Feretti & Giovannini 2008;Brunetti et al 2008), excess of extreme-ultraviolet (EUV) and hard X-ray radiation (Bowyer & Berghöfer 1998;Lieu et al 1999;Fusco-Femiano 2004). Another consequence of the presence of cosmic rays in the ICM is the production of gamma rays.…”

Section: Cosmic Ray Pressurementioning

confidence: 99%

On the influence of non-thermal pressure on the mass determination of galaxy clusters

Laganá

Keller

2010

A&A

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Aims. Given that in most cases just thermal pressure is taken into account in the hydrostatic equilibrium equation to estimate galaxy cluster mass, the main purpose of this paper is to consider the contribution of all three non-thermal components to total mass measurements. The non-thermal pressure is composed by cosmic rays, turbulence and magnetic pressures. Methods. To estimate the thermal pressure we used public XMM-Newton archival data of five Abell clusters to derive temperature and density profiles. To describe the magnetic pressure, we assume a radial distribution for the magnetic field, B(r) ∝ ρ α g . To seek generality we assume α within the range of 0.5 to 0.9, as indicated by observations and numerical simulations. Turbulent motions and bulk velocities add a turbulent pressure, which is considered using an estimate from numerical simulations. For this component, we assume an isotropic pressure, P turb = 1 3 ρ g (σ 2 r + σ 2 t ). We also consider the contribution of cosmic ray pressure, P cr ∝ r −0.5 . Thus, besides the gas (thermal) pressure, we include these three non-thermal components in the magnetohydrostatic equilibrium equation and compare the total mass estimates with the values obtained without them. Results. A consistent description for the non-thermal component could yield a variation in mass estimates that extends from 10% to ∼30%. We verified that in the inner parts of cool core clusters the cosmic ray component is comparable to the magnetic pressure, while in non-cool core clusters the cosmic ray component is dominant. For cool core clusters the magnetic pressure is the dominant component, contributing more than 50% of the total mass variation due to non-thermal pressure components. However, for non-cool core clusters, the major influence comes from the cosmic ray pressure that accounts for more than 80% of the total mass variation due to non-thermal pressure effects. For our sample, the maximum influence of the turbulent component to the total mass variation can be almost 20%. Although all of the assumptions agree with previous works, it is important to notice that our results rely on the specific parametrization adopted in this work. We show that this analysis can be regarded as a starting point for a more detailed and refined exploration of the influence of non-thermal pressure in the intra-cluster medium (ICM).

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Section: Cosmic Ray Pressurementioning

confidence: 99%

On the influence of non-thermal pressure on the mass determination of galaxy clusters

Laganá

Keller

2010

A&A

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“…Their energy would amount to 1-10% of the thermal energy content of the ICM. The inverse Compton model was also favoured by Berghöfer (1998), andLieu et al (1999a) suggested that cosmic rays could be as energetically important as the thermal ICM. Lieu et al (1996a).…”

Section: The Firstmentioning

confidence: 99%

Soft X-Ray and Extreme Ultraviolet Excess Emission from Clusters of Galaxies

et al. 2008

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An excess over the extrapolation to the extreme ultraviolet and soft X-ray ranges of the thermal emission from the hot intracluster medium has been detected in a number of clusters of galaxies. We briefly present each of the satellites (EUVE, ROSAT PSPC and BeppoSAX, and presently XMM-Newton, Chandra and Suzaku) and their corresponding instrumental issues, which are responsible for the fact that this soft excess remains controversial in a number of cases. We then review the evidence for this soft X-ray excess and discuss the possible mechanisms (thermal and non-thermal) which could be responsible for this emission.

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“…However, Arabadjis & Bregman (2000) find significantly lower or even no additional absorbing column densities in a number of other clusters. A spatially extended EUV emission of non-thermal origin (Enßlin et al 1999, and references therein) above the expected flux from the hot X-ray gas in at least the Coma and possibly other clusters seems to be fairly established (Lieu et al 1996a,b;Mittaz et al 1998;Lieu et al 1999;Bowyer et al 1999), although an accompanying low energy X-ray excess emission is uncertain (Dixon et al 1996;Arabadjis & Bregman 1999). Overall, these observations indicate a striking departure from a nearly homogeneous intracluster gas towards a spatially inhomogeneous multiphase ICM (Bonamente et al 2001;Lieu et al 2000).…”

Section: Introductionmentioning

confidence: 98%

Far-infrared emission from intracluster dust in Abell clusters

Stickel

Klaas

Lemke

et al. 2002

A&A

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Abstract. The ISOPHOT instrument aboard ISO has been used to observe extended FIR emission of six Abell clusters. Strip scanning measurements with crossing position angles centered on the clusters were carried out at 120 µm and 180 µm. The raw profiles of the I120 µm/I180 µm surface brightness ratio including zodiacal light show a bump towards Abell 1656 (Coma), dips towards Abell 262 and Abell 2670, and are without clear structure towards Abell 400, Abell 496, and Abell 4038. After subtraction of the zodiacal light, the bump towards Abell 1656 is still present, while the dips towards Abell 262 and Abell 2670 are no longer noticable. This indicates a localized excess of emitting material outside the Galaxy towards Abell 1656 with properties different from the galactic foreground cirrus, while the behavior in Abell 262 and Abell 2670 can be reconciled with galactic cirrus structures localized on the line-of-sight to these clusters. The excess of ≈0.2 MJy/sr seen at 120 µm towards Abell 1656 (Coma) is interpreted as being due to thermal emission from intracluster dust distributed in the hot X-ray emitting intracluster medium. The integrated excess flux within the central region of 10 -15 diameter is ≈2.8 Jy. Since the dust temperature is poorly constrained, only a rough estimate of the associated dust mass of MD ≈ 10 7 M can be derived. The associated visual extinction is negligible (AV 0.1 mag) and much smaller than claimed from optical observations. No evidence is found for intracluster dust in the other five clusters observed. The absence of any signature for intracluster dust in five clusters and the rather low inferred dust mass in Abell 1656 indicates that intracluster dust is likely not responsible for the excess X-ray absorption seen in cooling flow clusters. These observations thereby represent a further unsuccessful attempt in detecting the presumed final stage of the cooling flow material, in accord with quite a number of previous studies in other wavelengths regions. Finally, the observed dimming of the high-redshift supernovae is unlikely be attributable to extinction caused by dust in the intracluster or even a presumed intercluster medium.

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Nonthermal Origin of the EUV and Soft X-Rays from the Coma Cluster:Cosmic Rays in Equipartition with the Thermal Medium

Cited by 69 publications

References 19 publications

On the influence of non-thermal pressure on the mass determination of galaxy clusters

On the influence of non-thermal pressure on the mass determination of galaxy clusters

Soft X-Ray and Extreme Ultraviolet Excess Emission from Clusters of Galaxies

Far-infrared emission from intracluster dust in Abell clusters

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