2001ApJ...553L.115M

We have used the ROSAT All-Sky Survey to detect a known supercluster at z=0.087 in the north ecliptic pole region. The X-ray data greatly improve our understanding of this supercluster's characteristics, approximately doubling our knowledge of the structure's spatial extent and tripling the cluster/group membership compared with the optical discovery data. The supercluster is a rich structure consisting of at least 21 galaxy clusters and groups, 12 active galactic nuclei, 61 IRAS galaxies, and various other objects. A majority of these components were discovered with the X-ray data, but the supercluster is also robustly detected in optical, IR, and UV wave bands. Extending 129x102x67 (h^–1₅₀Mpc)³, the north ecliptic pole supercluster has a flattened shape oriented nearly edge-on to our line of sight. Owing to the softness of the ROSAT X-ray passband and the deep exposure over a large solid angle, we have detected for the first time a significant population of X-ray-emitting galaxy groups in a supercluster. These results demonstrate the effectiveness of X-ray observations with contiguous coverage for studying structure in the universe.