Why Group_R_Crit200 is not the maximum at z=0. I noticed that it increases with time and then decreases at later redshifts. What is the reason for that? Shouldn't it always increase with time as the universe expands?
Thanks in advance,
You mean Group_R_Crit200 for one specific halo? Which one?
In general, for an isolated halo, you are right that M200 and R200 should just increase monotonically with time, as the halo grows. But if it isn't isolated for any reason, e.g. undergoes a merger with another halo, this may not be so simple.