enzohop

enzohop is a C++ wrapper around the HOP halo-finding code of Daniel Eisenstein and Wayne Hu (astro-ph/9712200). It is located in src/enzohop, and it uses the same makefile system as enzo, so if you can build enzo, enzohop should build easily. For those who are familiar with enzohop from the previous public release, this version is completely different and no longer uses any of the enzo routines to read the data files, which should make it easier to work with.

Note: Users are strongly encouraged to use yt to analyze their data. yt includes a nearly identical implementation of HOP. Once you have data in yt, it will be easier to make pipelines to analyze data than with this stand-alone enzohop. Here are some examples of what you can do with yt and HOP.

usage: ./enzohop.exe [options] HopDensityThreshold enzo_restart_file
example: ./enzohop.exe -p 80.0 data0100
   options are:
      -d(ebug)
      -s (include stars, default is dm-only grouping)
      -p (for packed HDF enzo files)

The HopDensityThreshold? value (a float) roughly determines the over density cutoff where HOP starts adding particles to a halo. Use the debug flag for highly verbose status messages. By default enzohop only considers the dark matter particles. You can also consider stars in the haloes with the -s flag. Use the -p flag when reading in packed AMR data sets.

enzohop creates these files:

* output_hop.den, output_hop.gbound, output_hop.hop, zregroup.gmerge, zregroup.size, zregroup.tag - Intermediate files created by HOP which are not for general human consumption.

* HopAnalysis.out - A text file containing the haloes ordered by particle count. Below is some sample output of this file. The last six columns give the spatial extrema of each halo. Note that haloes near the box edges have periodic boundary conditions taken into account, so the extrema may look backwards.

#Group  Mass            #part max dens   x            y            z            xmin         xmax         ymin         ymax         zmin         zmax
0       2.11752665e+11  922  8529.01074  0.947430193  0.800357342  0.613576591  0.920256674  0.981784761  0.771684229  0.8258847    0.587984562  0.635404706 
1       1.83962485e+11  801  8200.65527  0.179652691  0.762595236  0.647919178  0.144561067  0.215674877  0.743494391  0.786570013  0.622867763  0.673818707 
2       1.20803582e+11  526  4554.56104  0.553282857  0.323450834  0.152668178  0.527688324  0.570516348  0.305997729  0.341582775  0.124154508  0.174957782 

* Part-Final.txt - A text file containing five columns of data: unique particle ID, group assignment for that particle, and position (x,y,z) for that particle. This can be useful for tracking particles in time, or other kinds of statistics. There is a Halo Merger Tree code available using yt, which uses this functionality.