# Virialized dark matter halos

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1. Feb 2, 2016

Dear all,

I am new in the field of galaxy formation, so I am sorry if my questions are a bit simple.
-what does virialized halo mean? does it mean they obey the virial theorem concerning their kinetic and potential energy?
$$2<T>=n<V>$$
-Why should the halos be like this to merge and make galaxies?
-do you know any introductory book I could use in this?

2. Feb 2, 2016

### Chalnoth

Yes, it means they obey the virial theorem. It's expected that a self-gravitating gas cloud should relax into a state where it follows the virial theorem as it reaches equilibrium. However, it's known that the virial theorem frequently is inaccurate for real systems. For example, if a pair of galaxies have recently collided to form one larger galaxy, the resulting galaxy will not be very close to following the virial theorem for some time. It's a very useful approximation to make the math tractable, but not always accurate.

3. Feb 3, 2016