Emission line properties of the most luminous AGN in massive galaxies at
  intermediate redshifts
  We have analyzed the emission line properties of 6019 Type II AGN at
redshifts between 0.4-0.8 with [OIII] luminosities greater than 3x10^8 Lsun,
characteristic of the Type II quasars first identified in population studies by
Zakamska et al (2003). The AGN are drawn from the CMASS sample of galaxies with
stellar masses greater than 10^11 Msun that were studied as part of the Baryon
Oscillation Spectroscopic Survey (BOSS) and comprise 0.5% of the total
population of these galaxies. Individual spectra have low S/N, so the analysis
is carried out on stacked spectra in bins of [OIII] luminosity and estimated
stellar age. The emission line ratios of the stacks are well fit with simple
uniform-density photoionization models with metallicities between solar and
twice solar. In the stacks, a number of emission lines are found to have
distinct broad components requiring a double Gaussian rather than a single
Gaussian fit, indicative of outflowing ionized gas. These are: [OIII]4959,
[OIII]5007, [OII]3727,3729 and Halpha$. Higher ionization lines such as
[NeIII]3869 and [NeV]3345 are detected in the stacks, but are well fit by
single Gaussians. The broad components typically contain a third of the total
line flux and have widths of 600 km/s for the oxygen lines and 900 km/s for
Halpha. The fraction of the flux in the broad component and its width are
independent of [OIII] luminosity, stellar age, radio and mid-IR luminosity. The
stellar mass of the galaxy is the only parameter we could identify that
influences the width of the broad line component.
