The Presence of Weak Active Galactic Nuclei in High Redshift Star
  Forming Galaxies
  We present [OIII 5007A] observations of the star forming galaxy HDF-BMZ1299
(z=1.598) using Keck Observatory's Adaptive Optics system with the
near-infrared integral field spectrograph OSIRIS. Using previous Halpha and
[NII] measurements of the same source, we are able for the first time to use
spatially resolved observations to place a high-redshift galaxy's substructure
on a traditional HII diagnostic diagram. We find that HDF-BMZ1299's spatially
concentrated nebular ratios in the central ~1.5 kiloparsec (0."2) are best
explained by the presence of an AGN: log([NII]/Halpha)=-0.22+/-0.05 and 2sigma
limit of log([OIII]/Hbeta)>0.26. The dominant energy source of this galaxy is
star formation, and integrating a single aperture across the galaxy yields
nebular ratios that are composite spectra from both AGN and HII regions. The
presence of an embedded AGN in HDF-BMZ1299 may suggest a potential
contamination in a fraction of other high-redshift star forming galaxies, and
we suggest that this may be a source of the "elevated" nebular ratios
previously seen in seeing-limited metallicity studies. HDF-BMZ1299's estimated
AGN luminosity is L_Halpha = 3.7e41 erg/s and L_[OIII] = 5.8e41 erg/s, making
it one of the lowest luminosity AGN discovered at this early epoch.
