Infrared spectroscopy of nearby radio active early-type galaxies-II: spectral atlas

We present a near-infrared spectroscopic atlas of nearby, bright early-type galaxies with radio emission, containing 163 galaxies observed by the Palomar 200'' TripleSpec instrument, measuring the emission line fluxes for H, He, [Fe II], and H-2 and determined the nuclear excitation mechanisms. By stacking spectra, we deduced the H-2 excitation temperature (1957 +/- 182 K) 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 CO12 absorption line index versus 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 synchronized.