* Astronomy

Title: Discovery of a supercluster in the ZOA in Vela
Author: Renée C. Kraan-Korteweg, Michelle E. Cluver, Maciej Bilicki, Thomas H. Jarrett, Matthew Colless, Hans Böhringer, Gayoung Chon

We report the discovery of a potentially major supercluster that extends across the Galactic Plane in the constellation of Vela, at a mean recessional velocity of ~18,000 km/s. Recent multi-object spectroscopic observations of this Vela Supercluster (VSCL), using AAOmega+2dF and SALT, confirm an extended galaxy overdensity in the Zone of Avoidance (ZOA) located where residual bulk flows predict a considerable mass excess. We present a preliminary analysis of ~4500 new spectroscopic galaxy redshifts obtained in the ZOA centred on the Vela region (l=272.5°±20°,b=0°±10°). The presently sparsely-sampled dataset traces an overdensity that covers 25° in Galactic longitude on either side of the Plane, suggesting an extent of 25° x 20°, corresponding to ~115 x 90 h_70 Mpc at the supercluster redshift. In redshift space the overdensity appears to consist of two merging wall-like structures, interspersed with clusters and groups. Both the velocity histogram and the morphology of the multi-branching wall structure are consistent with a supercluster classification. K_s^o galaxy counts show an enhancement of ~1.2 over the survey area for galaxies brighter than M_{K}^* at the VSCL distance, and a galaxy overdensity of delta=0.50--0.77 within a photometric redshift shell around VSCL, when compared to various 2MASS samples. Taking account of selection effects, the VSCL is estimated to contribute v_LG \gtrsim 50 km/s to the motion of the Local Group.

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