A Redshift Survey of Obscured Galaxies

Abstract

One of the problems for studies of large scale structures in nearby space (cz < 10, 000 km/s) is the presence of the Zone of Avoidance which is so large and wide on the sky that potentially important clusters and large voids have remained undetected. A prime example was the Ophiuchus cluster (cz = 8, 500 km/s), discovered by Wakamatsu and Malkan (1981) as a heavily obscured cD cluster close to the Galactic centre region (l = 0.5º, b = +9.5º) and is the 2nd brightest X-ray cluster after the Perseus cluster (Okamura, 1991). A hidden galaxy survey was performed by visually searching ESO/SERC Sky Survey (R and J) copy films of the region centred at l = 355º, b = +10º finding more than 4000 galaxies in 6 fields. Several irregular clusters adjacent to Ophiuchus were found forming an Ophiuchus supercluster which may itself be connected to the Hercules supercluster by a wall structure parallel to the local supergalactic plane (Wakamatsu et al. 1994). In front of this supercluster, an ‘Ophiuchus Void’ is suggested (cz = 4, 500 km/s). The Ophiuchus supercluster at cz = 8, 500 km/s is similar to the Hercules supercluster (cz = 11, 000 km/s), and extends to the north toward the latter supercluster.