We construct a new analytic phenomenological model for the extended circumgalactic material ( CGM ) of L _ { * } galaxies .
Our model reproduces the OVII/OVIII absorption observations of the Milky Way ( MW ) and the OVI measurements reported by the COS-Halos and eCGM surveys .
The warm/hot gas is in hydrostatic equilibrium in a MW gravitational potential , and we adopt a barotropic equation of state , resulting in a temperature variation as a function of radius .
A pressure component with an adiabatic index of \gamma = 4 / 3 is included to approximate the effects of a magnetic field and cosmic rays .
We introduce a metallicity gradient motivated by the enrichment of the inner CGM by the Galaxy .
We then present our fiducial model for the corona , tuned to reproduce the observed OVI-OVIII column densities , and with a total mass of { M _ { CGM } } \approx 5.5 \times 10 ^ { 10 } M _ { \odot } inside { r _ { CGM } } \approx 280 kpc .
The gas densities in the CGM are low ( { n _ { H } } = 10 ^ { -5 } -3 \times 10 ^ { -4 } cm ^ { -3 } ) and its collisional ionization state is modified by the metagalactic radiation field ( MGRF ) .
We show that for OVI-bearing warm/hot gas with typical observed column densities N _ { OVI } \sim 3 \times 10 ^ { 14 } cm ^ { -2 } at large ( \gtrsim 100 kpc ) impact parameters from the central galaxies , the ratio of the cooling to dynamical times , { t _ { cool } } / { t _ { dyn } } , has a model-independent upper limit of \sim 5 .
In our model , { t _ { cool } } / { t _ { dyn } } at large radii is \sim 2 - 3 .
We present predictions for a wide range of future observations of the warm/hot CGM , from UV/X-ray absorption and emission spectroscopy , to dispersion measure ( DM ) and Sunyaev-Zeldovich CMB measurements .