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

TL;DR

This paper models a gravitational lensing scenario involving a high-redshift Lyman alpha emitter and a foreground galaxy, estimating a modest magnification factor due to the small stellar mass of the intervening galaxy.

Contribution

It presents the first gravitational lens model for an LAE-LAE system, estimating the lensing effect based on stellar mass and UV luminosity.

Findings

Magnification factor ranges from 1.01 to 1.16

Intervening galaxy's stellar mass is approximately 3.5x10^9 Msun

Lensing effect is modest due to small stellar mass

Abstract

During the course of our Lyman continuum imaging survey, we found that the spectroscopically confirmed Lya emitter LAE 221724+001716 at z = 3.10 in the SSA 22 field shows strong Lyman continuum emission (lambda_rest ~ 900 A) 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 lambda_obs ~ 3360 A is Lya. 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 Mstar ~ 3.5x10^9 Msun from its UV luminosity and ~ 3.0x10^7--2.4x10^9 Msun through the SED 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.