We present [ O iii 5007Å ] 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 H \alpha and [ N ii ] 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 H ii diagnostic diagram .
We find that HDF-BMZ1299 ’ s spatially concentrated nebular ratios in the central \sim 1.5 kiloparsec ( 0 \farcs 2 ) are best explained by the presence of an AGN : log ( [ N ii ] /H \alpha ) =-0.22 \pm 0.05 and 2 \sigma limit of log ( [ O iii ] /H \beta ) \gtrsim 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 H ii 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 _ { H \alpha } = 3.7x10 ^ { 41 } erg s ^ { -1 } and L _ { [ OIII ] } = 5.8x10 ^ { 41 } erg s ^ { -1 } , making it one of the lowest luminosity AGN discovered at this early epoch .