Hi, I am a new user of yt and I trying to run the yt-hop Halo Finder to build a merger history of halos. The output "HopAnalysis.out" I get following the instructions on: http://yt.enzotools.org/wiki/Recipes/HOPResults only contains a list of halo properties, not particle IDs. If there a way to access the IDs of particles in the halos, like in the original hop code? I would have expected this to be needed by the Galaxy/Halo Merger Tree code described in http://yt.enzotools.org/wiki/Recipes/GalaxyMerging. Thanks in advance for any suggestion, Michele Michele Trenti Center for Astrophysics and Space Astronomy University of Colorado 389 UCB Phone: +1 303-492-8490 Boulder, Colorado 80309-0389 Fax: +1 303-492-7178 USA E-mail: michele.trenti@colorado.edu "It often happens that a player carries out a deep and complicated calculation, but fails to spot something elementary right at the first move." -- Chess Grandmaster Alexander Kotov