Lyα-emitting galaxies as a probe of reionization: large-scale bubble morphology and small-scale absorbers
Abstract
The visibility of Lyα-emitting galaxies during the Epoch of Reionization is controlled by both diffuse H I patches in large-scale bubble morphology and small-scale absorbers. To investigate their impacts on Lyα transfer, we apply a novel combination of analytic modelling and cosmological hydrodynamical, radiative transfer simulations to three reionization models: (I) the `bubble' model, where only diffuse H I outside ionized bubbles is present; (II) the `web' model, where H I exists only in overdense self-shielded gas; and (III) the hybrid `web-bubble' model. The three models can explain the observed Lyα luminosity function equally well, but with very different H I fractions. This confirms a degeneracy between the ionization topology of the intergalactic medium (IGM) and the H I fraction inferred from Lyα surveys. We highlight the importance of the clustering of small-scale absorbers around galaxies. A combined analysis of the Lyα luminosity function and the Lyα fraction can break this degeneracy and provide constraints on the reionization history and its topology. Constraints can be improved by analysing the full MUV-dependent redshift evolution of the Lyα fraction of Lyman break galaxies. We find that the IGM-transmission probability distribution function is unimodal for bubble models and bimodal in web models. Comparing our models to observations, we infer that the neutral fraction at z ∼ 7 is likely to be of the order of tens of per cent when interpreted with bubble or web-bubble models, with a conservative lower limit ∼1 per cent when interpreted with web models.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- December 2016
- DOI:
- 10.1093/mnras/stw2193
- arXiv:
- arXiv:1510.05647
- Bibcode:
- 2016MNRAS.463.4019K
- Keywords:
-
- line: formation;
- radiative transfer;
- galaxies: high-redshift;
- intergalactic medium;
- cosmology: theory;
- dark ages;
- reionization;
- first stars;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 23 pages, 20 figures, submitted to MNRAS, Abstract abridged for arXiv submission