We present the results of structure analyses for a large sample of 426 Ly \alpha emitters ( LAEs ) at z \sim 2.2 that are observed with HST /ACS and WFC3-IR by deep extra-galactic legacy surveys .
We confirm that the merger fraction and the average ellipticity of LAE ’ s stellar component are 10 - 30 % and 0.4 - 0.6 , respectively , that are comparable with previous study results .
We successfully identify that some LAEs have a spatial offset between Ly \alpha and stellar-continuum emission peaks , \delta _ { Ly \alpha } , by \sim 2.5 - 4 kpc beyond our statistical errors .
To uncover the physical origin of strong Ly \alpha emission found in LAEs , we investigate Ly \alpha equivalent width ( EW ) dependences of these three structural parameters , merger fraction , \delta _ { Ly \alpha } , and ellipticity of stellar distribution in the range of EW ( { Ly \alpha } ) = 20 - 250 Å .
Contrary to expectations , we find that merger fraction does not significantly increase with Ly \alpha EW .
We reveal an anti-correlation between \delta _ { Ly \alpha } and EW ( { Ly \alpha } ) by Kolmogorov-Smirnov ( KS ) test .
There is a trend that the LAEs with a large Ly \alpha EW have a small ellipticity .
This is consistent with the recent theoretical claims that Ly \alpha photons can more easily escape from face-on disks having a small ellipticity , due to less inter-stellar gas along the line of sight , although our KS test indicates that this trend is not statistically significant .
Our results of Ly \alpha -EW dependence generally support the idea that an H i column density is a key quantity determining Ly \alpha emissivity .