| Speaker: Renée C. Kraan-Korteweg (University of Cape Town)
I will give a brief overview of the current status of the mapping of the Great Attractor (GA) mass overdensity which is mostly hidden from our view by the Milky Way. The combined results from optical, NIR (FIR, X-ray) and in particular the systematic Parkes HI surveys find the GA to consist of a nearby Great-Wall like structure that crosses the Zone of Avoidance diagonally.
However, questions like "how massive is the GA really" and "who is pulling in the Zone of Avoidance", the so-called GA versus Shapley controversy, still remain unanswered. To try to address this, a deep NIR imaging survey of 37.5 square degrees was performed along the most opaque part of the Great Attractor Wall. Independently an attempt was made at deriving the peculiar velocity flow fields around the nominal center of the GA from the near-infrared (NIR) Tully-Fisher relation of HI detected galaxies "in" the Zone of Avoidance. The imaging survey finds clear evidence for an overall density enhancement at the GA distance though no further clusters were identified apart from some at higher redshifts. A mass estimate of the GA Wall will be presented. The TF analysis shows some signature of back-flow, but it is too sparsely sampled to provide conclusive evidence.
If time permits I will hint at some of tug-and-war in this area that is happening at even larger distances and how future SKA Pathfinder HI surveys may resolve this controversy.
|Renée C. Kraan-Korteweg