•Dynamical estimates of
cluster masses
–Virial Theorem as we
have discussed, but…
•Very few clusters exist
that can be well done!
•E.g, which are cluster
members?
•Must measure many
velocities
•
–Case of Coma
•Regular rich cluster,
looks like isothermal sphere
•Crossing time arguments
OK
•Virial mass issue for
Coma first by Zwicky (1937)
•Surface distribution,
velocities in next figure…