Identify the mechanism responsible for rovibrational H2 decoupling

Identify the physical origin of the decoupling between the higher rovibrational H2 transitions and the pure rotational and lower rovibrational transitions in the nuclear regions of the observed AGN-hosting dwarf galaxies.

Background

The H2 excitation diagrams show that a single-temperature model describes the pure rotational and lower v = 1–0 rovibrational transitions, while higher rovibrational transitions lie above the rotational curve. Comparable behavior has been attributed in other systems either to shock heating associated with radio jets or to sub-thermal excitation in low-density gas.

Because the observations do not cover the low-J pure rotational lines, the authors cannot determine which mechanism produces the decoupling in these dwarf galaxies. Resolving the issue requires additional spectral coverage and excitation diagnostics.