New insights into the Triangulum Australis supercluster of galaxies

Abstract

The Triangulum Australis cluster is one of about a dozen nearby massive cluster systems which contribute to the gravitational pull behind the so-called Great Attractor that is dominated by the nearby Shapley Supercluster mass, which conforms the galaxy velocity flows observed in that general direction. Here, we study the structure and dynamical mass of the Triangulum Australis cluster together with the neighbouring cluster AS0794. We present a set of 131 velocities collected in the regions of the two clusters with the 2.5 m Du Pont telescope at Las Campanas Observatory (Chile). For the Triangulum Australis cluster we find a dynamical mass of about Mv = 4.2 (±1.3) × 1015 M⊙ and for AS0794 a value of about Mv = 1.7 (±1.3) × 1013 M⊙. These values are consistent with the observed X-ray luminosities of these clusters. Combined with velocities already known we reanalyse the structure and dynamics of this general region, finding that both clusters, together with at least eight other ones, form a large supercluster, centered on TriAus (which dominates in terms of mass). We find that this supercluster is part of a large-scale structure filament linked to the Shapley supercluster (SSC). Uncertainties remain on the richness and detailed structure of this filament and the TriAus supercluster because parts of it remain hidden behind the Galaxy disk.