Understand
The recent detection of ULASJ1342+0928, a bright QSO at $z=7.54$, provides a powerful probe of the ionisation state of the intervening intergalactic medium, potentially allowing us to set strong constraints on the epoch of reionisation (EoR).
- Here we quantify the presence of Ly$\alpha$ damping wing absorption from the EoR in the spectrum of ULASJ1342+0928.
- Our Bayesian framework simultaneously accounts for uncertainties on: (i) the intrinsic QSO emission (obtained from reconstructing the Ly$\alpha$ profile from a covariance matrix of emission lines) and (ii) the distribution of HII regions during reionisation (obtained from three different 1.6$^3$ Gpc$^3$ simulations spanning the range of plausible EoR morphologies).
- Our analysis is complementary to that in the discovery paper (Ba\~nados et al.) and the accompanying method paper (Davies et al.) as it focuses solely on the damping wing imprint redward of Ly$\alpha$ ($1218 < \lambda < 1230$\AA), and uses a different methodology for (i) and (ii).