Virial temperature
= Virial temperature
{title2=$T_{\rm vir}$}
The <virial temperature> characterizes the thermal energy of gas supported in a gravitational potential. It is of order $\mu m_pGM/(k_BR)$, with a structural coefficient determined by the density profile. For a uniform self-gravitating gas sphere the <virial theorem> gives $k_BT=GM\mu m_p/(5R)$; a conventional halo circular-speed definition often uses $k_BT\simeq\mu m_pv_c^2/2$.