Detection of Lyman-alpha Emission from a Triply Imaged z = 6.85 Galaxy behind MACS J2129.4-0741

Journal
Date Issued
2016
Author(s)
Huang, Kuang-Han
•
Lemaux, Brian C.
•
Schmidt, Kasper B.
•
Hoag, Austin
•
Bradač, Maruša
•
Treu, Tommaso
•
Dijkstra, Mark
•
•
Henry, Alaina
•
Malkan, Matthew
•
Mason, Charlotte
•
Morishita, Takahiro
•
•
Ryan, Russell E., Jr.
•
Trenti, Michele
•
Wang, Xin
DOI
Abstract
We report the detection of Lyα emission at ∼9538 Å in the Keck/DEIMOS and Hubble Space Telescope WFC3 G102 grism data from a triply imaged galaxy at z=6.846+/- 0.001 behind galaxy cluster MACS J2129.4-0741. Combining the emission line wavelength with broadband photometry, line ratio upper limits, and lens modeling, we rule out the scenario that this emission line is [O II] at z = 1.57. After accounting for magnification, we calculate the weighted average of the intrinsic Lyα luminosity to be ∼ 1.3× {10}42 {erg} {{{s}}}-1 and Lyα equivalent width to be 74 ± 15 Å. Its intrinsic UV absolute magnitude at 1600 Å is -18.6 ± 0.2 mag and stellar mass (1.5+/- 0.3)× {10}7\quad {M}☉ , making it one of the faintest (intrinsic {L}{UV}∼ 0.14 {L}{UV}\ast ) galaxies with Lyα detection at z∼ 7 to date. Its stellar mass is in the typical range for the galaxies thought to dominate the reionization photon budget at z≳ 7; the inferred Lyα escape fraction is high (≳ 10%), which could be common for sub-L* z≳ 7 galaxies with Lyα emission. This galaxy offers a glimpse of the galaxy population that is thought to drive reionization, and it shows that gravitational lensing is an important avenue for probing the sub-L* galaxy population.
Volume
823
Issue
1
Start page
L14
Uri
Url
Issn Identifier
2041-8205
Ads BibCode
2016ApJ...823L..14H
Rights
open.access
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