Exploring the nature of the Lyman-$\alpha$ emitter CR7

Understand

CR7 is the brightest Lyman-$\alpha$ emitter observed at $z>6$, which shows very strong Lyman-$\alpha$ and HeII 1640\AA\ line luminosities, but no metal line emission.

• Previous studies suggest that CR7 hosts either young primordial stars with a total stellar mass of $\sim 10^7\,\mathrm{M}_\odot$ or a black hole of $\gtrsim 10^6\,\mathrm{M}_\odot$.
• Here, we explore different formation scenarios for CR7 with a semianalytical model, based on the random sampling of dark matter merger trees.
• We are unable to reproduce the observational constraints with a primordial stellar source, given our model assumptions, due to the short stellar lifetimes and the early metal enrichment.