Hi Nick, I don't have a great answer for why those differ. I don't think anyone on this list is an expert in the inner workings of HOP or Rockstar. The fact that HOP and 1.5xRockstar agree so well for large radii is suggestive of a missing little h somewhere. I assume that both of their virial radius calculations are done with spherical overdensities. It may be worth taking a few cases and using the HaloCatalog to calculate a similar R200. There a way to do that here: https://yt-astro-analysis.readthedocs.io/en/latest/halo_catalogs.html#recipe... Sorry, that's not a great answer. Britton On Wed, Jul 31, 2019 at 6:10 PM Nick Gnedin <gnedin@fnal.gov> wrote:

Folks,

I ran both HOP and Rockstar halo finders on the same ART simulations, and the mass functions match very well (attached hmf_m.pdf file). However, when I compare virial radii (attached hmf_r.pdf file), they don't match. Even if I try rescaling the Rockstar virial radius by 1.5, the match is much worse than for mass functions.

How are the 'virial_radius' fields defined for both halo finders?

This is a z=7 simulations, so all mass definitions are the same, Mvir = M200m = M200c.

I also attach the script to plot virial radii if you want to check it, although it is trivial.

Many thanks (as usual),

Nick

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