A Gravitational Lens Model for the Lyα Emitter LAE 221724+001716 at z = 3.1 in the SSA 22 Field

Abstract

During the course of our Lyman continuum imaging survey, we found that the spectroscopically confirmed Lyα emitter LAE 221724+001716 at z = 3.10 in the SSA 22 field shows strong Lyman continuum emission (λ_rest ~ 900 Å) that escapes from this galaxy. However, another recent spectroscopic survey revealed that the supposed Lyman continuum emission could arise from a foreground galaxy at z = 1.76 if the emission line newly detected from the galaxy at λ_obs ≈ 3360 Å is Lyα. If this is the case, as the angular separation between these two galaxies is very small (≈0.''6), LAE 221724+001716 at z = 3.10 could be amplified by the gravitational lensing caused by this intervening galaxy. Here we present a possible gravitational lens model for the system of LAE 221724+001716. First, we estimate the stellar mass of the intervening galaxy as M _sstarf ~ 3.5 × 10⁹ M _⊙ from its UV luminosity and ~3.0 × 10⁷-2.4 × 10⁹ M _⊙ through the spectral energy distribution fitting. Then, we find that the gravitational magnification factor ranges from 1.01 to 1.16 using the so-called singular isothermal sphere model for strong lensing. While LAE 221724+001716 is the first system of an LAE-LAE lensing reported so far, the estimated magnification factor is not so significant because the stellar mass of the intervening galaxy is small.