LAGER Lyα Luminosity Function at z ∼ 7: Implications for Reionization

• Published in: The Astrophysical journal Vol. 927; no. 1; pp. 36 - 50
• Main Authors: Wold, Isak G. B., Malhotra, Sangeeta, Rhoads, James, Wang, Junxian, Hu, Weida, Perez, Lucia A., Zheng, Zhen-Ya, Khostovan, Ali Ahmad, Walker, Alistair R., Barrientos, L. Felipe, González-López, Jorge, Harish, Santosh, Infante, Leopoldo, Jiang, Chunyan, Pharo, John, Moya-Sierralta, Cristóbal, Bauer, Franz E., Galaz, Gaspar, Valdes, Francisco, Yang, Huan
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01-03-2022; IOP Publishing
• Subjects: Astronomy & Astrophysics; ASTRONOMY AND ASTROPHYSICS; Astrophysics; Cosmos; Emitters; Galaxies; Galaxy evolution; High-redshift galaxies; Hydrogen; Intergalactic media; Ionization; Luminosity; Luminosity function; Lyman-alpha galaxies; Polls & surveys; Red shift; Reionization
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ac4997

Abstract
We present a new measurement of the Ly
α
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 × 10
6
Mpc
3
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 Ly
α
emitter (LAEs) candidates, characterize our survey’s completeness and reliability, and compute Ly
α
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 Ly
α
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 1
σ
.