@prefix pubblicazioni: . @prefix unitaDiPersonaleInterno: . @prefix prodotto: . unitaDiPersonaleInterno:MATRICOLA1831 pubblicazioni:autoreCNRDi prodotto:ID5720 . @prefix rdf: . prodotto:ID5720 rdf:type prodotto:TIPO1101 . @prefix retescientifica: . prodotto:ID5720 rdf:type retescientifica:ProdottoDellaRicerca . @prefix rdfs: . prodotto:ID5720 rdfs:label "Chandra Study of an Overdensity of X-Ray Sources around Two Distant (Z~0.5) Clusters (Articolo in rivista)"@en . @prefix xsd: . prodotto:ID5720 pubblicazioni:anno "2001-01-01T00:00:00+01:00"^^xsd:gYear . @prefix skos: . prodotto:ID5720 skos:altLabel "
Cappi, M.; Mazzotta, P.; Elvis M, Burke D.J., Comastri A., Fiore F., et al. (2001)
Chandra Study of an Overdensity of X-Ray Sources around Two Distant (Z~0.5) Clusters
"^^rdf:HTML ; pubblicazioni:autori "Cappi, M.; Mazzotta, P.; Elvis M, Burke D.J., Comastri A., Fiore F., et al."^^xsd:string ; pubblicazioni:paginaInizio "624"^^xsd:string ; pubblicazioni:paginaFine "638"^^xsd:string ; pubblicazioni:numeroVolume "548"^^xsd:string ; skos:note "ISI Web of Science (WOS)"^^xsd:string ; pubblicazioni:affiliazioni "IASF-CNR, Bologna; Harvard-Smithsonian Center for Astrophysics (CfA); \nInstitute for Astronomy, Hawai; Osservatorio Astronomico di Bologna; \nOsservatorio Astronomico di Roma; SRON."^^xsd:string ; pubblicazioni:titolo "Chandra Study of an Overdensity of X-Ray Sources around Two Distant (Z~0.5) Clusters"^^xsd:string . @prefix prodottidellaricerca: . prodotto:ID5720 prodottidellaricerca:abstract "We present results from a Chandra X-Ray Observatory study of the field X-ray source populations in four different observations: two high-redshift (z~0.5) clusters of galaxies 3C 295 and RX J003033.2+261819; and two noncluster fields with similar exposure time. Surprisingly, the 0.5-2 keV source surface densities (~900-1200 sources deg-2 at a flux limit of 1.5\u00D710-15 ergs cm-2 s-1) measured in an ~8'\u00D78' area surrounding each cluster exceed by a factor of ~2 the value expected on the basis of the ROSAT and Chandra logN-logS, with a significance of ~2 sigma each, or ~3.5 sigma when the two fields are combined (i.e., a probability to be a statistical fluctuation of <1% and <0.04%, respectively). The same analysis performed on the noncluster fields and on the outer chips of the cluster fields does not show evidence of such an excess. In both cluster fields, the summed 0.5-10 keV spectrum of the detected objects is well fitted by a power law with Gamma~1.7 similar to active galactic nuclei (AGNs) and shows no sign of intrinsic absorption. The few (~10 of 35) optical identifications available to date confirm that most of them are, as expected, AGNs, but the number of redshifts available is too small to allow conclusions on their nature. We discuss possible interpretations of the overdensity in terms of a statistical variation of cosmic background sources; a concentration of AGNs and/or powerful starburst galaxies associated with the clusters; and gravitational lensing of background QSOs by the galaxy clusters. All explanations, however, are difficult to reconcile with the large number of excess sources detected. Deeper X-ray observations and more redshifts measurements are clearly required to settle the issue." . @prefix istituto: . prodotto:ID5720 prodottidellaricerca:prodottoDi istituto:CDS005 ; pubblicazioni:autoreCNR unitaDiPersonaleInterno:MATRICOLA1831 . @prefix parolechiave: . prodotto:ID5720 parolechiave:insiemeDiParoleChiave . istituto:CDS005 prodottidellaricerca:prodotto prodotto:ID5720 . parolechiave:insiemeDiParoleChiaveDi prodotto:ID5720 .