Zero halo_axisA values in halo catalog about halotools HOT 3 CLOSED

This is useful to know. Halotools just directly uses the publicly available Rockstar subhalo catalogs, so these outlier halos are inherited from the upstream data. I'm not sure what failure mode this would signify. One innocuous explanation would be that these halos are perfect spheres. What are their values of b/a and c/a?

Regardless, probably the simplest treatment is as you say: to just mask out the outlier halos before proceeding with any further preprocessing.

from halotools.

For these 39 halos, the 'halo_b_to_a' and 'halo_c_to_a' values are all zero.

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Hmm, ok, thanks for checking. I would have guessed that if these were perfect spheres then c/a and b/a would be unity, not zero. But of course it's possible that when Rockstar encounters such a rare edge case, it just uses zero for the fill value instead of unity. It's good that you raised this issue in case other people encounter it and go poking around for whether it has been noticed before. But since this is such a tiny fraction of objects, presumably throwing these subhalos out will not impact a cosmological analysis, so I think we should close this issue for now until we find that this is creating some downstream problem.

from halotools.