Phase Diagram: Physical Internal Energy vs. COMOVING Gas Density

Now the Gadget particles internal energy is multiplied by $m/\rho dv$, where $m$ is the mass of the particle, $\rho$ is the density of the particle and $dv$ is the volume of a cell in the Cholla simulation, this way the particles with “larger volume” will have more weight.

Here is the opposite, the internal energy of the particles is divided by $m/\rho dv$.