Hydrogen reionization ends by z = 5.3: Lyman-α optical depth measured by the XQR-30 sample

• DOI: 10.1093/mnras/stac1046
• Publication Date: 2022-04-18T19:09:40Z
• Authors: Sarah E I Bosman; Frederick B Davies; George D Becker; Laura C Keating; Rebecca L Davies; Yongda Zhu; Anna-Christina Ei...; Valentina D’Odorico; Fuyan Bian; Manuela Bischetti; Stefano V Cristiani; Xiaohui Fan; Emanuele P Farina; Martin G Haehnelt; Joseph F Hennawi; Girish Kulkarni; Andrei Mesinger; Romain A Meyer; Masafusa Onoue; Andrea Pallottini; Yuxiang Qin; Emma Ryan-Weber; Jan-Torge Schindler; Fabian Walter; Feige Wang; Jinyi Yang
• Keywords: Opacity

The presence of excess scatter in the Ly-$\alpha$ forest at $z\sim 5.5$, together with existence sporadic extended opaque Gunn-Peterson troughs, has started to provide robust evidence for a late end hydrogen reionisation. However, low data quality and systematic uncertainties complicate use transmission as precision probe reionisation's stages. In this paper, we assemble sample 67 quasar sightlines $z>5.5$ high signal-to-noise ratios $>10$ per $\leq 15$ km s$^{-1}$ spectral pixel, relying largely on new XQR-30 sample. is large program VLT/X-Shooter which obtained deep (SNR $>20$ pixel) spectra 30 quasars $z>5.7$. We carefully account systematics continuum reconstruction, instrumentation, contamination by damped systems. present improved measurements mean over $4.9<z<6.1$. Using all known forward modelling analysis, find excellent agreement between observed distributions homogeneous-UVB simulations Sherwood Nyx up $z\leq5.2$ ($<1 \sigma$), mild tension ($\sim 2.5 \sigma$) $z=5.3$. Homogeneous UVB models are ruled out $z\geq5.4$ confidence ($>3.5 \sigma$). Our results indicate that reionisation-related fluctuations, whether UVB, residual neutral fraction, and/or IGM temperature, persist intergalactic medium until least $z=5.3$ ($t=1.1$ Gyr after Big Bang). This further