Redshifts of galaxies vs halos

[Aleksandra Kusiak]

Hi,
I am trying to populate some halos with an HOD using halotools, and I started with this example before putting my own data:

https://halotools.readthedocs.io/en/stable/quickstart_and_tutorials/tutorials/catalog_analysis/galcat_analysis/basic_examples/clustering_examples/galaxy_catalog_analysis_tutorial9.html

I followed each step here, particularly specifying the redshift=0 for the Bolshoi halos. Maybe I am not understanding something correctly, but why are the galaxy redshifts (the outputs of mock_survey.ra_dec_z) not the same as the redshifts of the halos (zero in this case)? I attach the distribution of the redshifts of galaxies, which goes up to z=0.07 when shifting the catalog.
I tried both with and without shifting, and also for Bolshoi at z=0.5. Does it have to do with peculiar velocities (in any case, it seems like a significant difference)?

Please let me know what I am missing here, Thank you!

[Andrew Hearin]

Hi @olakusiak the mock survey function transforms your box into a lightcone, and so as the line-of-sight serves as the redshift direction. So even in the complete absence of peculiar velocities, the redshift histogram would look something like what you report.