IGM damping wing constraints on reionisation from covariance reconstruction of two $z\gtrsim7$ QSOs

Abstract

Bright, high redshift (z > 6) QSOs are powerful probes of the ionisation state of the intervening intergalactic medium (IGM). The detection of Lyα damping wing absorption imprinted in the spectrum of high-z QSOs can provide strong constraints on the epoch of reionisation (EoR). In this work, we perform an independent Lyα damping wing analysis of two known z > 7 QSOs; DESJ0252-0503 at z = 7.00 (Wang et al.) and J1007+2115 at z = 7.51 (Yang et al.). For this, we utilise our existing Bayesian framework which simultaneously accounts for uncertainties in: (i) the intrinsic Lyα emission profile (reconstructed from a covariance matrix of measured emission lines; extended in this work to include N V) and (ii) the distribution of ionised (H II) regions within the IGM using a 1.6 3 Gpc 3 reionisation simulation. This approach is complementary to that used in the aforementioned works as it focuses solely redward of Lyα (1218 < λ < 1230 Å) making it more robust to modelling uncertainties while also using a different methodology for (i) and (ii). We find, for a fiducial EoR morphology, xH I = 0.64 +0.19 −0.23 (68 per cent) at z = 7 and xH I = 0.27 +0.21 −0.17 at z = 7.51 consistent within 1σ 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 (Bañados et al.) finding xH I = 0.44 +0.23 −0.24 at z = 7.09 and xH I = 0.31 +0.18 −0.19 at z = 7.54. Finally, we combine the QSO damping wing constraints for all four z 7 QSOs to obtain a single, unified constraint of xH I = 0.49 +0.11 −0.11 at z = 7.29.

Constraining the reionization and thermal history of the Universe using a semi-numerical photon-conserving code SCRIPT

“…The end of reionization, in particular, is quite tightly constrained around 𝑧 6 which, as we will discuss later, is a consequence of including the temperature measurements at 𝑧 ∼ 5.5 in the analysis. For comparison, we also plot constraints on the ionized fraction obtained from studies not considered in our analysis, e.g., those from the damping wing signatures in the quasar spectra (Davies et al 2018;Greig et al 2021a) and from the Ly𝛼 emission detected in Lyman-break galaxies (Mason et al 2018;Bolan et al 2021). As is clear from the figure, these constraints are consistent with those obtained from our analysis.…”

Modelling the star-formation activity and ionizing properties of high-redshift galaxies

“…At relatively lower redshifts (5.4 ≤ z ≤ 6), we use the recent findings from a study of a large sample of quasar absorption spectra taken with the X-Shooter and ESI instruments [108], combined with a radiative transfer code to model the Lyman-α opacities. For higher redshifts (z ≥ 6), we use the constraints on Q HI derived from Lyman-α damping wing observations of individual or stacked samples of high redshift quasars [109][110][111], and a collection of UV-bright galaxies observed with the JWST [112]. It is worth mentioning that all the constraints on Q HI used in this work are model-dependent, and hence one must be careful in interpreting the results.…”