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The total mass derived from X-ray emission is biased low in a large number of clusters when compared with the mass estimated via strong and weak lensing. Suzaku and Chandra observations out to the virial radius report in several relaxed clusters' steep temperature gradients that on assuming pure thermal hydrostatic equilibrium (HE) imply an unphysically decreasing mass profile. Moreover, the gas mass fraction appears to be inconsistent with the cosmic value measured from the cosmic microwave background. Such findings can be interpreted as evidence for an additional nonthermal pressure in the outskirts of these clusters. This nonthermal component may be due to turbulence stirred by residual bulk motions of extragalactic gas infalling into the cluster. Here, we present a SuperModel analysis of A1835 observed by Chandra out to the virial radius. The SuperModel formalism can include in the equilibrium a nonthermal component whose level and distribution are derived imposing that the gas mass fraction (f gas) equals the cosmic value at the virial radius. Including such a nonthermal component, we reconstruct from X-rays an increasing mass profile consistent with the HE also in the cluster outskirts and in agreement at the virial boundary with the weak-lensing value. The increasing f gas profile confirms that the baryons are not missing but located at the cluster outskirts.
Fusco‐Femiano et al. (Fri,) studied this question.