LAGER Lyα Luminosity Function at z 7: Implications for Reionization
Abstract
We present a new measurement of the Lyα luminosity function (LF) at redshift z = 6.9, finding moderate evolution from z = 5.7 that is consistent with a fully or largely ionized z ~ 7 intergalactic medium. Our result is based on four fields of the LAGER (Lyman Alpha Galaxies in the Epoch of Reionization) project. Our survey volume of 6.1 × 106 Mpc3 is double that of the next largest z ~ 7 survey. We combine two new LAGER fields (WIDE12 and GAMA15A) with two previously reported LAGER fields (COSMOS and CDFS). In the new fields, we identify N = 95 new z = 6.9 Lyα emitter (LAEs) candidates, characterize our survey's completeness and reliability, and compute Lyα LFs. The best-fit Schechter LF parameters for all four LAGER fields are in good general agreement. Two fields (COSMOS and WIDE12) show evidence for a bright-end excess above the Schechter function fit. We find that the Lyα luminosity density declines at the same rate as the UV continuum LF from z = 5.7 to 6.9. This is consistent with an intergalactic medium that was fully ionized as early as redshift z ~ 7 or with a volume-averaged neutral hydrogen fraction of x H I < 0.33 at 1σ.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 2022
- DOI:
- 10.3847/1538-4357/ac4997
- arXiv:
- arXiv:2105.12191
- Bibcode:
- 2022ApJ...927...36W
- Keywords:
-
- High-redshift galaxies;
- Lyman-alpha galaxies;
- Reionization;
- Luminosity function;
- Galaxy evolution;
- 734;
- 978;
- 1383;
- 942;
- 594;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 19 pages, 11 figures