A spectroscopic search for AGN activity in the reionization era

Understand

The ubiquity of Lyman alpha (Ly$\alpha$) emission in a sample of four bright [O III]-strong star-forming galaxies with redshifts above 7 has led to the suggestion that such luminous sources represent a distinct population compared to their fainter, more numerous, counterparts.

• The presence of Ly$\alpha$ emission within the reionization era could indicate that these sources created early ionized bubbles due to their unusually strong radiation, possibly due to the presence of active galactic nuclei.
• To test this hypothesis we have secured long integration spectra with XSHOOTER on the VLT for three $z\simeq$7 sources selected to have similar luminosities and prominent excess fluxes in the IRAC 3.6 or 4.5$\mu$m band, usually attributed to strong [O III] emission.
• We secured additional spectroscopy for one of these galaxies at $z$=7.15 using MOSFIRE at the Keck telescope.