An analogous plot to Figure 3 in the paper, which shows oxygen ion-by-ion cooling and photo-heating, but here for the 5 primordial ions in solar abundance gas. In general the agreement is excellent: identical ion-by-ion cooling rates where both Gnat Ferland (2012) and our rates overlap in the top panel, CIE ionisation fractions compared to CLOUDY calculations (dotted lines) in the 2nd panel, and PIE ionisation fraction compared in the 4th panel, using the Haardt & Madau (2001) EGB at nH=10-4 cm-3. Disagreement arises at low temperatures for CIE, because ion-ion collisional ionisations are not tracked in our method and are outside of our range of interest. Our summed total primordial cooling curve for the CIE case is shown in the 3rd panel (thick black line) against CLOUDY CIE calculations (thick grey line) and the agreement is excellent (the grey line is completely overlapped). A similar comparison is done for PIE in the 5th panel, but here cooling (dashed thick lines) and photo-heating (dotted thick lines) are differenced to achieve net cooling (solid lines). Ion-by-ion contributions to cooling are shown as in the 3rd panel, but not for photo-heating. The agreement with CLOUDY is again excellent, although slight deviations allow one to notice the CLOUDY grey comparison curves. The equilibrium point where net cooling is zero for the primordial species occurs at T=104.7 K, which is about 3 times higher than for the total solar enriched gas.
