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maho3 / ltu-cmass

A modular simulator of CMASS-NGC galaxy clustering
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Fix comoving -> peculiar velocities #7

Closed maho3 closed 4 months ago

maho3 commented 4 months ago

In current comparisons with Quijote, it seems that the particle velocities output from pmwd and BORG are comoving velocities, not peculiar velocities as originally thought. The evidence for this has come from comparing halo catalogs with Quijote.

This task is to double-check this comparison and make sure we are using the right thing. For reference, the conversion goes as:

$$v{\rm pec} = (1+z) v{\rm com}$$

For the z=0 snapshots, this is the same, but for CMASS at z=0.5 if will be biased.

DeaglanBartlett commented 4 months ago

Looks like this is true, so I will add this correction

DeaglanBartlett commented 4 months ago

PR #9 solves this for Quijote. Still need to correct this for methods which call rho_to_halo.

maho3 commented 4 months ago

This has been corrected in cmass.nbody models in the last couple commits.