Details

Autor(en) / Beteiligte

• Mahdavi, Andisheh
• Hoekstra, Henk
• Babul, Arif
• Balam, David D
• Capak, Peter L

Titel

A Dark Core in Abell 520

Ist Teil von

• The Astrophysical journal, 2007-10, Vol.668 (2), p.806-814

Ort / Verlag

Chicago, IL: IOP Publishing

Erscheinungsjahr

2007

Quelle

Elektronische Zeitschriftenbibliothek (Open access)

Beschreibungen/Notizen

• The rich cluster Abell 520 (z = 0.201) exhibits truly extreme and puzzling multiwavelength characteristics. It may best be described as a "cosmic train wreck." It is a major merger showing abundant evidence for ram pressure stripping, with a clear offset in the gas distribution compared to the galaxies (as in the Bullet Cluster, 1E 0657-558). However, the most striking feature is a massive dark core (721 h sub(70) M [unk]/L [unk] sub(B)) in our weak-lensing mass reconstruction. The core coincides with the central X-ray emission peak, but is largely devoid of galaxies. An unusually low mass-to-light ratio region lies 500 kpc to the east, and coincides with a shock feature visible in radio observations of the cluster. Although a displacement between the X-ray gas and the galaxy/dark matter distributions may be expected in a merger, a mass peak without galaxies cannot be easily explained within the current collisionless dark matter paradigm. Interestingly, the integrated gas mass fraction ( approximately 0.15), mass-to-light ratio (220 h sub(70) M [unk]/L [unk] sub(B)), and position on the X-ray luminosity-temperature and mass-temperature relations are unremarkable. Thus, gross properties and scaling relations are not always useful indicators of the dynamical state of clusters.