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Seminari INAF
Neutral islands and large-scale correlations in the Lyman-alpha forest: new constraints on the end of reionization
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Europe/Rome
Sala Jappelli (Osservatorio astronomico di Padova)
Sala Jappelli
Osservatorio astronomico di Padova
Description
The Lyman-alpha forest in high-redshift quasar spectra is a key observational tool to study the tail end of the Epoch of Reionization (EoR). In particular, the presence of Gunn-Peterson troughs with lengths up to ~100 comoving Mpc suggests the existence of extended neutral regions and large-scale correlations in the intergalactic medium (IGM) near the reionization boundary.
I will present two complementary results from high-S/N, high-resolution quasar spectra from the XQR-30 sample and additional VLT/X-Shooter and Keck/ESI data, that address both the ionization state and the coherence scale of the IGM at 5 < z < 6. First, by stacking Lyman-alpha forest dark-gap edges adjacent to Gunn–Peterson troughs, we detect a stochastic damping-wing signal at z ~ 5.6 and infer a model-independent neutral fraction of x_HI = 0.19 ± 0.07 (1σ) with x_HI < 0.44 at z = 5.9, demonstrating the presence of neutral islands close to the end of reionization and favoring a late-and-slow scenario. Second, we measure the redshift-dependent correlation length of Lyman-alpha transmission by fitting the flux-correlation matrix with an MCMC framework and benchmarking against 1.5 Gpc³ reionization lightcones. We find strong, rapidly increasing correlations toward higher redshift, from L ≤ 26.5 (68.5) Mpc (1σ/2σ) at z = 5.0 to L = 253 (+273/-42) Mpc at z = 6.1, exceeding <60 Mpc predicted by current simulations incorporating UV background fluctuations and neutral islands. These results jointly imply (i) substantial residual neutrality at 5.6 < z < 6 and (ii) IGM coherence on >200 Mpc scales at z ~ 6, setting hard requirements on simulation volumes and suggesting missing large-scale physics in standard EoR models.
I will present two complementary results from high-S/N, high-resolution quasar spectra from the XQR-30 sample and additional VLT/X-Shooter and Keck/ESI data, that address both the ionization state and the coherence scale of the IGM at 5 < z < 6. First, by stacking Lyman-alpha forest dark-gap edges adjacent to Gunn–Peterson troughs, we detect a stochastic damping-wing signal at z ~ 5.6 and infer a model-independent neutral fraction of x_HI = 0.19 ± 0.07 (1σ) with x_HI < 0.44 at z = 5.9, demonstrating the presence of neutral islands close to the end of reionization and favoring a late-and-slow scenario. Second, we measure the redshift-dependent correlation length of Lyman-alpha transmission by fitting the flux-correlation matrix with an MCMC framework and benchmarking against 1.5 Gpc³ reionization lightcones. We find strong, rapidly increasing correlations toward higher redshift, from L ≤ 26.5 (68.5) Mpc (1σ/2σ) at z = 5.0 to L = 253 (+273/-42) Mpc at z = 6.1, exceeding <60 Mpc predicted by current simulations incorporating UV background fluctuations and neutral islands. These results jointly imply (i) substantial residual neutrality at 5.6 < z < 6 and (ii) IGM coherence on >200 Mpc scales at z ~ 6, setting hard requirements on simulation volumes and suggesting missing large-scale physics in standard EoR models.
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https://unipd.zoom.us/j/85273198731?pwd=V1ZiNE9ZWUN4ZTdIUzJsTFo0Z3U2Zz09
Meeting ID: 852 7319 8731
Passcode: 208186
Meeting ID: 852 7319 8731
Passcode: 208186
Organised by
Paolo Cassata
Prof.
