NIR spectral atlas of early-type galaxies

By stacking spectra, we deduced the H_2_ excitation temperature (1957+/-182K) and dominant excitation mechanism (thermal and shock heating combined) from the K-band emission line sequence.

Stacking also produces an 'average' spectrum of absorption features and spectral indices from the literature; the CO^12^ absorption line index vs. J-K colour shows a trend of stronger nuclear activity producing a weaker CO12 index and a redder (flatter) continuum. The correlations between the radio and the emission-line luminosities finds a trend with radio power; however, the large scatter in the upper limits shows that the two are not directly coupled and the duty cycles of SF and AGN activity are not synchronised.