The most distant cluster of Galaxy ever detected ?

ALBACETE-COLOMBO J.F., J.A. COMBI, P. TOZZI, J. LOPEZSANTIAGO, G.E. ROMERO , J. MARTI, P. BENAGLIA & S.A. CORA

Granada, Espana

Congreso; The X-ray Universe 2008; 2008

Agencia Espacial Europea - Consorcio XMM-Newton

We investigate the nature of an extended X-ray source serendipitously discovered by the use of a 38 ks off-axis XMM-Newton observation. Its central X-ray emission is most likely due to an AGN, while the faint and extended X-ray morphology can be possibly interpreted as ICM.No clear optical and near-IR counterpart of the X-ray source is detected in deep images available. X-ray spectrum shows a clear signature of the FeK 6.7 keV line complex [6.7+6.9 keV in rest frame], redshifted at the energy of 2.1keV: z~2.15±0.08 !. A double-peakof FeK 6.7 keV emission was found, but displaced from the maximum of the extended 0.3-12keV emission. Total X-ray spectrum (AGN+ICM) was fitted to a temperature kTx~2.8 ±0.7 keV, while diffuse X-ray spectrum (ICM alone) seems to be characterized by a similar, but lower value, kTgas~2.2±1.1 keV. If the nature of the object is confirmed as a cluster of galaxies, it would constitute the highest z-detection from ICM, with an invaluable impact for cosmology.