def Trho_iddeg(rho,mu,mu_e):
T = <NUM_LIT> * rho**(old_div(<NUM_LIT>,<NUM_LIT>)) * mu / mu_e**(old_div(<NUM_LIT>,<NUM_LIT>))<EOL>return T<EOL>
T(rho) that separates ideal gas and degenerate pressure dominated regions.

Kippenhahn & Weigert, Eq. 16.6

Parameters
----------
rho : float
    Density array [cgs].
mu : float
    Mean molecular weight.
mu_e : float
    Mean molecular weight per free electron.