2016A&A...587A.138B

We present near-infrared (NIR) H+K-band long-slit spectra of eleven galaxies that were obtained with SOFI at the NTT (ESO). The galaxies are chosen from the low-luminosity type-1 quasi-stellar object (LLQSO) sample, which comprises the 99 closest (z≤0.06) QSOs from the Hamburg/ESO survey for bright UV-excess QSOs. These objects are ideal targets to study the gap between local Seyfert galaxies and high-redshift quasars because they show much stronger AGN activity than local objects, but are still close enough for a detailed structural analysis. We fit hydrogen recombination, molecular hydrogen, and [FeII] lines after carefully subtracting the continuum emission. From the broad Paα components, we estimated black hole masses and enlarged the sample of LLQSOs that deviate from the M_BH-L_bulge relations of inactive galaxies from 12 to 16 objects. All objects show emission from hot dust (T∼1200K) as well as stellar contribution. However, the respective fractions vary strongly among the objects. More than half of the objects show H₂ emission lines, which indicate a large reservoir of molecular gas that is needed to feed the AGN and star formation. In the NIR diagnostic diagram all objects lie in the location of AGN-dominated objects. However, most of the objects show indications of star formation activity, suggesting that their offset location with respect to M_BH-L_bulge relations of inactive galaxies may be a consequence of overluminous bulges.