We present deep rest-frame UV spectroscopic observations using the Gran Telescopio Canarias of six gravitationally lensed Ly \alpha emitters ( LAEs ) at 2.36 < z < 2.82 selected from the BELLS GALLERY survey .
By taking the magnifications into account , we show that LAEs can be as luminous as L _ { Ly \alpha } \simeq 30 \times 10 ^ { 42 } erg s ^ { -1 } and M _ { UV } \simeq - 23 ( AB ) without invoking an AGN component , in contrast with previous findings .
We measure Ly \alpha rest-frame equivalent widths , EW _ { 0 } ~ { } ( Ly \alpha ) , ranging from 16Å to 50Å and Ly \alpha escape fractions , f _ { esc } ~ { } ( Ly \alpha ) , from 10 % to 40 % .
Large EW _ { 0 } ~ { } ( Ly \alpha ) and f _ { esc } ~ { } ( Ly \alpha ) are found predominantly in LAEs showing weak low-ionization ISM absorption ( EW _ { 0 } \lesssim 1 Å ) and narrow Ly \alpha profiles ( \lesssim 300 km s ^ { -1 } FWHM ) with their peak close ( \lesssim 80 km s ^ { -1 } ) to their systemic redshifts , suggestive of less scatter from low H i column densities that favours the escape of Ly \alpha photons .
We infer stellar metallicities of Z / Z _ { \odot } \simeq 0.2 in almost all LAEs by comparing the P-Cygni profiles of the wind lines N v 1240Å and C iv 1549Å with those from stellar synthesis models .
We also find a trend between M _ { UV } and the velocity offset of ISM absorption lines , such as the most luminous LAEs experience stronger outflows .
The most luminous LAEs show star formation rates up to \simeq 180 M _ { \odot } yr ^ { -1 } , yet they appear relatively blue ( \beta _ { UV } \simeq - 1.8 to -2.0 ) showing evidence of little dust attenuation ( E ( B - V ) = 0.10 - 0.14 ) .
These luminous LAEs may be particular cases of young starburst galaxies that have had no time to form large amounts of dust .
If so , they are ideal laboratories to study the early phase of massive star formation , stellar and dust mass growth , and chemical enrichment histories of starburst galaxies at high- z .