Hi all, I'm working on a script to calculate star formation rates for halos in different mass bins from Enzo simulation ouput. As part of the script, I need to access the dynamical_time values for all of the star particles associated with a given halo. The halos have been previously stored to disk, so I'm loading them with LoadHaloes and then for each halo identifying the star particles with the typical stars = halo["creation_time"] > 0 mask. When I try to get the associated dynamical times with halo["dynamical_time"][stars] I get -99999. instead of the expected values. When I perform the same operation on the entire dataset instead of an individual halo I get the correct dynamical times, so the values I want do exist. I was testing out different fields with halo[field][stars] to see if I could find any patterns, and I noticed that for all the fields that are actually saved to disk for the halos (creation_time, ParticleMassMsun, particle_positions, etc.) I get values that match those in the halo hdf5 files. However, this is not true for "particle_index", where I get incorrect values. The values do correspond to particles in the halo, but they aren't the indices of the star particles. I'm not sure, but I assume this is why I'm getting incorrect values for dynamical_time which isn't saved in the halo hdf5 files. I'm not familiar enough with the code for the halo finder to know where to start looking for the source of this problem. Does anyone with more experience have an idea? My version of yt is a copy of 2.6.1 that I updated about 3 weeks ago. Thanks. - Josh