Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, The Netherlands and the United Kingdom) and with the participation of ISAS and NASA.

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The two components of NGC 3690 have been observed separately NGC 3690A and NGC 3690BC. In the analysis we treat them as two separate systems.

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... galaxies

Previously published H₂molecular lines are not shown here. The spectra can be found in: Rigopoulou et al. (1996) for NGC 3256, Kunze et al. (1996) for NGC 4038/39, Spoon et al. (2000) for NGC 4945.

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... cases

We note that the assumption of LTE conditions implies densities higher than about n>10⁴ cm^-3which may not be present if a diffuse component contributes significantly. In that case the excitation diagram can still be used as an empirical tool although the interpretation of excitation temperatures is not straightforward.

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