A mature cluster with X-ray emission at z=2.07 (R. Gobat et al.)

Vol. 526In section 3. Cosmology

A mature cluster with X-ray emission at z=2.07

by R. Gobat, E. Daddi, M. Onodera, A. Finoguenov, A. Renzini, N. Arimoto, R. Bouwens, M. Brusa, R.-R. Chary, A. Cimatti, M. Dickinson, X. Kong, and M. Mignoli, A&A 526, A133 alt

Structures form hierarchically in the universe, and it is expected that most clusters form after a redshift z=2. This is why it has been difficult until now to detect distant galaxy clusters. The authors have discovered what appears as the most distant and the most mature galaxy cluster to date at z=2.07, showing that large clusters had already been formed at this early epoch. For that, they assembled evidence from strong (20sigma) galaxy over density, coincidence of redshifts with VLT spectroscopy, and X-ray diffuse emission expected from a cluster with the XMM satellite.