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Visualisations of 6dF data

Visualisations of 6dF data. by A.P. Fairall Using ‘Labyrinth’ software developed by Carl Hultquist and Samesham Perumal Departments of Astronomy and Computer Science University of Cape Town. An introduction to Labyrinth.

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Visualisations of 6dF data

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  1. Visualisations of 6dF data by A.P. Fairall Using ‘Labyrinth’ software developed by Carl Hultquist and Samesham Perumal Departments of Astronomy and Computer Science University of Cape Town

  2. An introduction to Labyrinth This software allows one to visualise a galaxy database from any chosen position, looking in any chosen direction. One can also interactively fly around the database (although the presentation here uses still frames).

  3. Lets start by looking at some (non-6dF) data with the galaxies Represented as white points

  4. The readouts in the lower left corner give direction of view and position in Cartesian Supergalactic coordinates

  5. Labels can be turned on to identify features

  6. Colour coding can be introduced to represent distance. Nearest galaxies red, distant galaxies blue

  7. This enables a steroscopic view of the distribution using ChromoDepth™ spectacles

  8. But instead of this distracting false colour…

  9. ..we change the coding to white (near) to blue (far), which works with or without spectacles

  10. Labyrinth also lets us fade background structures…

  11. Now we see only the nearest galaxies, which can also be shown ..

  12. ..as billboards, with images to scale, so giving a realistic visualisation of extragalactic space.

  13. But the main purpose of Labyrinth is to grow “Tully bubbles” around groups and clusters of galaxies

  14. This is 6dF data!

  15. The bubbles can be made completely opaque

  16. The individual galaxies need not be shown

  17. The Software identifies Minimal Spanning Trees (MSTs) and wraps a surface around them. A minimum number of galaxies per MST can be specified

  18. The MSTs are specified by a percolation radius (r) At cz = 0 To compensate for the diminishing density of data with increasing redshift, the percolation radius is increased with incresing cz. In this way the average density of bubbles stays more or less constant with increasing distance

  19. As the bubbles grow, they interconnect to reveal the web of large-scale structures

  20. Now to 6dF! We begin by taking 6dF data with cz < 7500 km/s so to examine very nearby large-scale structures.

  21. The view is looking back from a point at cz = 20000 km/s in the direction of the North Celestial Pole

  22. Northern Galactic Hemisphere at top Southern Galactic Hemisphere at bottom

  23. Now to switch on the colour coding

  24. True stereoscopy can be obtained by viewing these images With ChromoDepth spectacles

  25. Individual galaxies

  26. Mimimal spanning trees show the densest regions in the data

  27. The percolation distance r is set at 5 km/s

  28. The minimum number of galaxies per MST is set at 10

  29. As we increase the percolation distance, so the structures grow. Here it is r = 10 km/s

  30. r = 20 km/s

  31. r = 30 km/s

  32. r = 40 km/s

  33. r = 50 km/s

  34. r = 60 km/s

  35. r = 70 km/s

  36. Much more Detail can be Seen than was Previously possible r = 80 km/s

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