The north ecliptic pole supercluster

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 ou r understanding of this supercluster's characteristics, approximately doubl ing our knowledge of the structure's spatial extent and tripling the cluste r/group membership compared with the optical discovery data. The superclust er 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. E xtending 129 x 102 x 67 (h(50)(-1) Mpc)(3), the north ecliptic pole supercl uster has a flattened shape oriented nearly edge-on to our line of sight. O wing 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 pop ulation of X-ray-emitting galaxy groups in a supercluster. These results de monstrate the effectiveness of X-ray observations with contiguous coverage for studying structure in the universe.