Diagnostics for PopIII galaxies and Direct Collapse Black Holes in the early universe

Understand

Forthcoming observational facilities will make the exploration of the early universe routine, likely probing large populations of galaxies at very low metallicities.

• It will therefore be important to have diagnostics that can solidly identify and distinguish different classes of objects in such low metallicity regimes.
• We use new photoionisation models to develop diagnostic diagrams involving various nebular lines.
• We show that combinations of these diagrams allow the identification and discrimination of the following classes of objects in the early universe: PopIII and Direct Collapse Black Holes (DCBH) in pristine environments, PopIII and DCBH embedded in slightly enriched ISM (Z~10^{-5}-10^{-4}), (metal poor) PopII and AGN in enriched ISM.