VLT/UVES spectrosc. in Orion. II. HH204

We kinematically isolate the high-velocity emission of HH 204 from the emission of the background nebula and study the subarcsecond distribution of physical conditions and ionic abundances across the HH object.

We find that low- and intermediate-ionization emission arises exclusively from gas at photoionization equilibrium temperatures, whereas the weak high-ionization emission from HH 204 shows a significant contribution from higher-temperature shock-excited gas. We separately derive the ionic abundances of HH 204, the emission of the Orion Nebula, and the fainter diffuse blue layer. In HH 204, the O^+^ abundance determined from collisional excited lines matches the one based on recombination lines, while the O^2+^ abundance is very low, so that the oxygen abundance discrepancy is zero.