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astropy / halotools

Python package for studying large scale structure, cosmology, and galaxy evolution using N-body simulations and halo models
http://halotools.rtfd.org
BSD 3-Clause "New" or "Revised" License
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All upid values are -1 when using SubhaloPhaseSpace #1024

Open nvanalfen opened 3 years ago

nvanalfen commented 3 years ago

Low priority issue, but confusing enough that I thought I'd submit an issue so it's documented.

When using SubhaloPhaseSpace (not sure it this also happens with others), the upid value for all of the satellite galaxies is -1. My understanding is that this upid == -1 indicates that the subhalo is a host halo (the highest in the halo hierarchy), basically a shorthand for saying halo_id == halo_hostid. However, all the satellites are getting upid == -1 even though their halo_id != halo_hostid.

Shortened version: Rather than getting the halo_id for their host halo in the halo_upid column, satellite galaxies are getting upid == -1 when using SubhaloPhaseSpace.

aphearin commented 3 years ago

Thanks for the reminder in the form of an issue @nvanalfen - this will be a simple fix, and I tagged this with next-release to make sure it makes it into v0.8.