Detect multiple overdensities in frame (Voronoi etc)

[Gabriel-p]

Check the Voronoi tessellation method:

• Seems simple enough to follow and apply: Finding galaxy clusters using Voronoi tessellations
• Compares several methods of clustering: A Comparative Study of Density Field Estimation for Galaxies (Full PDF)
• Finding structures in photometric redshift galaxy surveys: An extended friends-of-friends algorithm (Full PDF)
• Application of the Voronoi Tessellation Technique for Galaxy Cluster Search in the Münster Red Sky Survey
• ORCA: The Overdense Red-sequence Cluster Algorithm
• A reliable cluster detection technique using photometric redshifts: introducing the 2TecX algorithm

Somewhat related to #164.

[Gabriel-p]

See implementation of Voronoi algorithm here: https://github.com/Gabriel-p/voronoi

Implementation using KDE here: https://gist.github.com/Gabriel-p/17e67b705d12f7c05293

[Gabriel-p]

The Voronoi algorithm to detect the maximum spatial overdensity in a frame should work as follows:

• Calculate the average cell area for the frame either by averaging all the areas or by calculating the average Voronoi polygon area of a 2D Poisson distribution.
• In the params_input.dat file the user should select between the modes low, mid, high, man, which determine how the overdensities detection will work.
• If the global mode auto and low, mid, high are selected then the algorithm should detect an overdensity if these conditions are met:
  • low: all cells have at most 1.5*average_area and a minimum of 10 members (defined as cells sharing at least one vortex)
  • mid: all cells having at most average_area and a minimum of 25 members
  • high: all cells having at most 0.5*average_area and a minimum of 100 members
  • man: select both parameters p*average_area & N_min members
• Select as the main overdensity that which displays the highest concentration, defined as: (total members)/(total area).
• If the global mode semi is set, then use low, mid, high, man the same way but use the center & radius values in the semi_input.dat file to assign as the main overdensity that which lies closer to the center value within the radius given. If only the center value is given then search the entire frame. If none is given, default back to auto global mode and select the overdensity with the highest concentration..

[Gabriel-p]

User should handle this