Public Data Access Overview / Discussion Forum

Hi, Dylan!

How to calculate the maximum circular velocity (V_max) of halos in TNG100-dark or TNG100?

I am looking forward to your reply. Thank you.

There is the catalog quantity SubhaloVmax. Is this what you refer to?

Yes, my question is whether 'the maximum circular velocity' mentioned in the literature refers to SubhaloVmax in the TNG simulation, where
V_max = (GM(r_max)/r_max)^1/2

The circular velocity profiles of the halos obtained from the dark matter distribution, V^2 =GM(r)/r, have a well-defined maximum, which serves as a natural halo size scale denoted as V_max.

Also, is there V_200 = (GM(r_200)/r_200)^1/2 in the TNG simulation? Here 200 is 200 times the cosmic critical density.

I am looking forward to your reply. Thank you.

Yes SubhaloVmax is sqrt(GM/R) where the mass and radius correspond to the distance where the enclosed mass is maximal.

If you want a different value, or want to double-check it is what you expect, you can recalculate it from the snapshot data.

For your second question, M200 and R200 are available as Group_M_Crit200 and Group_R_Crit200 in the catalogs, so you can compute V200.

Thanks a lot for your help.

Best regards!