IGM damping wing constraints on reionization from covariance reconstruction of two <i>z</i> ≳ 7 QSOs
Bradley Greig, Andrei Mesinger, Frederick B. Davies, Feige Wang, Jinyi Yang, Joseph F. Hennawi
Abstract
ABSTRACT Bright, high-redshift (z &gt; 6) QSOs are powerful probes of the ionization state of the intervening intergalactic medium (IGM). The detection of Ly α 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 α damping wing analysis of two known z &gt; 7 QSOs; 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 α 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 1.63 Gpc3 reionization simulation. This approach is complementary to that used in the aforementioned works as it focuses solely redward of Ly α (1218 &lt; λ &lt; 1230 Å) 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 Mh ≳ 109 M⊙ haloes, $\bar{x}_{\mathrm{H\, {\scriptscriptstyle I}}{}} = 0.64\substack{+0.19 \\-0.23}$ (68 per cent) at z = 7 and $\bar{x}_{\mathrm{H\, {\scriptscriptstyle I}}{}} = 0.27\substack{+0.21 \\-0.17}$ 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 $\bar{x}_{\mathrm{H\, {\scriptscriptstyle I}}{}} = 0.44\substack{+0.23 \\-0.24}$ at z = 7.09 and $\bar{x}_{\mathrm{H\, {\scriptscriptstyle I}}{}} = 0.31\substack{+0.18 \\-0.19}$ 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 $\bar{x}_{\mathrm{H\, {\scriptscriptstyle I}}{}} = 0.49\substack{+0.11 \\-0.11}$ at z = 7.29.