Free Access

Fig. 1


Redshift distribution of the 198 known QSOs at z> 5.5 (black histogram) and of the 29 QSOs observed in the X-rays (red shaded histogram). The blue shaded histogram shows the distribution of the 18 sources detected at >3σ.

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.