Hi all, I am concerned about the velocity unit when yt reads EAGLE simulation. To convert the on-disk peculiar velocity (call this raw_velocity) to a physical velocity [cm/s]: physical velocity [cm/s] = raw_velocity * sqrt(a) * 1e5 When I specify: ad['PartType0','Velocity'].in_units('km/s') The output says it is in km/s, so I would expect this is the physical velocity. However, the output actually does not multiply the raw_velocity by sqrt(a) Looking at the source code (and its comments), I am not sure if this is intentional, or is this sqrt(a) accidentally missed out. https://github.com/yt-project/yt/blob/master/yt/frontends/gadget/data_struct... Line 490-499 A possibly relevant discussion (several years ago) with Gadget using yt (this is now fixed): https://bitbucket.org/yt_analysis/yt/pull-requests/1710/gadget-cosmology-sim... So, does yt intentionally not to multiply the velocity unit by sqrt(a) factor, or is the factor accidentally missed out? This could be confusing for relative new users like myself. Apologize if this is well known for experts. Thanks, Stephanie