IGM damping wing constraints on reionization from covariance reconstruction of two z ≳ 7 QSOs

Bright, high-redshift (z > 6) QSOs are powerful probes of the ionization state of the intervening intergalactic medium (IGM). The detection of Ly a damping wing absorption imprinted in the spectrum of high-z QSOs can provide strong constraints on the epoch of reionization (EoR). In this work, we perform an independent Ly alpha damping wing analysis of two known z > 7 QS05; DESJ0252-0503 at z = 7.00 (Wang et al.) and J1007+2115 at z = 7.51 (Yang et al.). For this, we utilize our existing Bayesian framework which simultaneously accounts for uncertainties in: (i) the intrinsic Ly alpha emission profile (reconstructed from a covariance matrix of measured emission lines; extended in this work to include N v) and (ii) the distribution of ionized (H II) regions within the IGM using a 1.6(3) Gpc(3) reionization simulation. This approach is complementary to that used in the aforementioned works as it focuses solely redward of Ly alpha (1218 < lambda < 1230 angstrom) making it more robust to modelling uncertainties while also using a different methodology for (i) and (ii). We find, for an EoR morphology driven by galaxies within M-h greater than or similar to 10(9) M-circle dot haloes, (x) over barH(I) = 0.64(-0.23)(+0.19) (68 percent) at z = 7 and (x) over barH(I) = 0.27(-0.17)(+0.21) at z = 7.51 consistent within 1 sigma to the previous works above, though both are slightly lower in amplitude. Following the inclusion of N v into our reconstruction pipeline, we perform a reanalysis of ULASJ1120+0641 at z = 7.09 (Mortlock et al.) and ULASJ1342+0928 at z = 7.54 (Bafiados et al.) finding (x) over barH(I )= 0.44(-0.24)(+0.23) at z = 7.09 and (x) over barH(I) = 0.31(-0.19)(+0.18 )at z = 7.54. Finally, we combine the QSO damping wing constraints for all four z greater than or similar to 7 QSO5 to obtain a single, unified constraint of (x) over barH(I) = 0.49(-0.11)(+0.11) at z = 7.29.