We report the discovery of an extremely long (~110 Mpc h-1) and dark (τ eff ≳ 7) Lyα trough extending down to z ≃ 5.5 towards the zem ≃ 6.0 quasar ULAS J0148+0600. We use these new data in combination with Lya forest measurements from 42 quasars at 4.5 ≤ zem ≤ 6.4 to conduct an updated analysis of the line-of-sight variance in the intergalactic Lya opacity over 4 ≤ z ≤ 6. We find that the scatter in transmission among lines of sight near z ~ 6 significantly exceeds theoretical expectations for either a uniform ultraviolet background (UVB) or simple fluctuating UVB models in which the mean free path to ionizing photons is spatially invariant. The data, particularly near z ≃ 5.6-5.8, instead require fluctuations in the volume-weighted hydrogen neutral fraction that are a factor of 3 or more beyond those expected from density variations alone.We argue that these fluctuations are most likely driven by large-scale variations in the mean free path, consistent with expectations for the final stages of inhomogeneous hydrogen reionization. Even by z ≃ 5.6, however, a large fraction of the data are consistent with a uniform UVB, and by z ~ 5 the data are fully consistent with opacity fluctuations arising solely from the density field. This suggests that while reionization may be ongoing at z ~ 6, it has fully completed by z ~ 5.

Becker, G., Bolton, J., Madau, P., Pettini, M., Ryan-Weber, E., Venemans, B. (2015). Evidence of patchy hydrogen reionization from an extreme Lyα trough below redshift six. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 447(4), 3402-3419 [10.1093/mnras/stu2646].

Evidence of patchy hydrogen reionization from an extreme Lyα trough below redshift six

Madau P.;
2015

Abstract

We report the discovery of an extremely long (~110 Mpc h-1) and dark (τ eff ≳ 7) Lyα trough extending down to z ≃ 5.5 towards the zem ≃ 6.0 quasar ULAS J0148+0600. We use these new data in combination with Lya forest measurements from 42 quasars at 4.5 ≤ zem ≤ 6.4 to conduct an updated analysis of the line-of-sight variance in the intergalactic Lya opacity over 4 ≤ z ≤ 6. We find that the scatter in transmission among lines of sight near z ~ 6 significantly exceeds theoretical expectations for either a uniform ultraviolet background (UVB) or simple fluctuating UVB models in which the mean free path to ionizing photons is spatially invariant. The data, particularly near z ≃ 5.6-5.8, instead require fluctuations in the volume-weighted hydrogen neutral fraction that are a factor of 3 or more beyond those expected from density variations alone.We argue that these fluctuations are most likely driven by large-scale variations in the mean free path, consistent with expectations for the final stages of inhomogeneous hydrogen reionization. Even by z ≃ 5.6, however, a large fraction of the data are consistent with a uniform UVB, and by z ~ 5 the data are fully consistent with opacity fluctuations arising solely from the density field. This suggests that while reionization may be ongoing at z ~ 6, it has fully completed by z ~ 5.
Articolo in rivista - Articolo scientifico
Cosmology: observations; Dark ages; First stars; Intergalactic medium; Large-scale structure of Universe; Quasars: absorption lines; Reionization;
English
2015
447
4
3402
3419
none
Becker, G., Bolton, J., Madau, P., Pettini, M., Ryan-Weber, E., Venemans, B. (2015). Evidence of patchy hydrogen reionization from an extreme Lyα trough below redshift six. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 447(4), 3402-3419 [10.1093/mnras/stu2646].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/452357
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