Abstract

We present near-IR photometry and spectroscopy of 30 extremely luminous radio and mid-IR-selected galaxies. With bolometric luminosities exceeding similar to 10(13) and redshifts ranging from z = 0.880 to 2.853, we use Very Large Telescope instruments X-shooter and Infrared Spectrometer and Array Camera to investigate this unique population of galaxies. Broad multicomponent emission lines are detected in 18 galaxies and we measure the near-IR lines H beta,[O III] lambda lambda 4959, 5007 and in 6, 15, and 13 galaxies, respectively, with 10 Ly alpha and 5 CIV lines additionally detected in the UVB arm. We use the broad [O III] lambda 5007 emission lines as a proxy for the bolometric active galactic nucleus luminosity, and derive lower limits to supermassive black hole masses of 10(7.9)-10(9.4)M(circle dot) with expectations of corresponding host masses of 10(10.4)-10(12.0)M(circle dot). We measure lambda(Edd) > 1 for eight of these sources at a 2 sigma significance. Near-IR photometry and SED fitting are used to compare stellar masses directly. We detect both Balmer lines in five galaxies and use these to infer a mean visual extinction of A(V) = 2.68 mag. Due to non-detections and uncertainties in our H beta emission line measurements, we simulate a broad H beta line of FWHM = 1480 kms(-1) to estimate extinction for all sources with measured H alpha emission. We then use this to infer a mean A(V) = 3.62 mag, demonstrating the highly obscured nature of these galaxies, with the consequence of increasing our estimates of black hole masses by a 0.5 orders of magnitude in the most extreme and obscured cases.