IGM damping wing constraints on the tail end of reionisation from the enlarged XQR-30 sample

The attenuation of Ly photons by neutral hydrogen in the intergalactic medium (IGM) at z5 continues to be a powerful probe for studying the epoch of reionisation. Given a framework to estimate the intrinsic (true) Ly emission of high-z sources, one can infer the ionisation state of the IGM during reionisation. In this work, we use the enlarged XQR-30 sample of 42 high-resolution and high-SNR QSO spectra between 5. 8\, z\, 6. 6 obtained with VLT/X-Shooter to place constraints on the IGM neutral fraction. This is achieved using our existing Bayesian QSO reconstruction framework which accounts for uncertainties such as the: (i) posterior distribution of predicted intrinsic Ly emission profiles (obtained via covariance matrix reconstruction of the Ly and N V emission lines from unattenuated high-ionisation emission line profiles; C IV, Si IV + O IV] and C III]) and (ii) distribution of ionised regions within the IGM using synthetic damping wing profiles drawn from a 1. 6³ Gpc³ reionisation simulation. Following careful quality control, we used 23 of the 42 available QSOs to obtain constraints/limits on the IGM neutral fraction during the tail-end of reionisation. Our median and 68th percentile constraints on the IGM neutral fraction are: 0. 20+0. 14\\-0. 12 and 0. 29+0. 14\\-0. 13 at z = 6. 15~and 6. 35. Further, we also report 68th percentile upper-limits of x₇\, ₈ < 0. 21, 0. 20, 0. 21 and 0. 18 at z = 5. 8, 5. 95, 6. 05~and 6. 55. These results imply reionisation is still ongoing at 5. 8\, z\, 6. 55, consistent with previous results from XQR-30 (dark fraction and Ly forest) along with other observational probes considered in the literature.