Stephen, I think I recall now that  the cutoff you mentioned is done in the filtering step, where if you specify the mass to be 10x the DM particle mass, then your halo will be at least 10 particles (if dm_only=True) etc, pretty vague in my memory.  So I guess what I can do is in my ellipsoidal analysis to discard/filter haloes that are less than 100 particles to be safe.

In addition to the particle count cutoff, currently I am also discarding all haloes that have C (the smallest axis) less than a cell width similar to what is done with spheres in YT.  I think this is a pretty problem dependent number that can vary depending on what the user want, but I was wondering if there's a general consensus on how many cells constitute a good enough ellipsoid?  I can throw in a switch for user to define this number as well.

As an alternative to cell count, I was thinking maybe if the volume of the "perfect" ellipsoid is a "close enough" fraction of the cell volume, then to keep the ellipsoid, else discard it.  This would be useful for keeping poorly resolve objects that exist in a couple cells and you'd think that it is big enough to consider all cells part of the object. In this case, the user would input the fraction instead of the cell count, what do you guys think?  

Any comments are appreciated.

From

G.S.