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

The attenuation of Ly alpha photons by neutral hydrogen in the intergalactic medium (IGM) at z greater than or similar to 5 continues to be a powerful probe for studying the epoch of reionization. Given a framework to estimate the intrinsic (true) Ly alpha emission of high-z sources, one can infer the ionization state of the IGM during reionization. In this work, we use the enlarged XQR-30 sample of 42 high-resolution and high signal-to-noise quasar spectra between 5.8 less than or similar to z less than or similar to 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 alpha emission profiles (obtained via covariance matrix reconstruction of the Ly alpha and N V emission lines from unattenuated high-ionization emission line profiles; C IV, Si IV + O IV], and C III]) and (II) distribution of ionized regions within the IGM using synthetic damping wing profiles drawn from a 1.6(3) Gpc(3) reionization 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 reionization. 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 (x) over bar (HI)<0.21, 0.20, 0.21, and 0.18 at z = 5.8, 5.95, 6.05, and 6.55. These results imply reionization is still ongoing at 5.8 less than or similar to z less than or similar to 6.55, consistent with previous results from XQR-30 (dark fraction and Ly alpha forest) along with other observational probes considered in the literature.