yt.lagos.FOFHaloFinder

class yt.lagos.FOFHaloFinder(pf, link=0.20000000000000001, dm_only=True, padding=0.02)

Friends-of-friends halo finder.

Halos are found by linking together all pairs of particles closer than some distance from each other. Particles may have multiple links, and halos are found by recursively linking together all such pairs.

Larger linking lengths produce more halos, and the largest halos become larger. Also, halos become more filamentary and over-connected.

Davis et al. “The evolution of large-scale structure in a universe dominated by cold dark matter.” ApJ (1985) vol. 292 pp. 371-394

Parameters :

pf : EnzoStaticOutput object

link : float

The interparticle distance (compared to the overall average) used to build the halos. Default = 0.2.

dm_only : bool

If True, only dark matter particles are used when building halos. Default = False.

padding : float

When run in parallel, the finder needs to surround each subvolume with duplicated particles for halo finidng to work. This number must be no smaller than the radius of the largest halo in the box in code units. Default = 0.02.

Examples :

——- :

>>> pf = load(“RedshiftOutput0000”) :

>>> halos = FOFHaloFinder(pf) :

Methods

nearest_neighbors_2D(haloID[, ...]) For a halo its nearest neighbors in 2D using the kd tree.
nearest_neighbors_3D(haloID[, ...]) For a halo its nearest neighbors in 3D using the kd tree.
write_out(filename) Write out standard halo information to a text file.
write_particle_lists(prefix) Write out the particle data for halos to HDF5 files.
write_particle_lists_txt(prefix) Write out the names of the HDF5 files containing halo particle data

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