We present the results from a VLT/SINFONI and Keck/NIRSPEC near-infrared spectroscopic survey of 16 Lyman-alpha emitters ( LAEs ) at z = 2.1 – 2.5 in the COSMOS and GOODS-N fields discovered from the HETDEX Pilot Survey .
We detect rest-frame optical nebular lines ( H \alpha and/or [ O iii ] \lambda 5007 ) for 10 of the LAEs and measure physical properties , including the star formation rate ( SFR ) , gas-phase metallicity , gas-mass fraction , and Ly \alpha velocity offset .
We find that LAEs may lie below the mass-metallicity relation for continuum-selected star-forming galaxies at the same redshift .
The LAEs all show velocity shifts of Ly \alpha relative to the systemic redshift ranging between +85 and +296 km s ^ { -1 } with a mean of +180 km s ^ { -1 } .
This value is smaller than measured for continuum-selected star-forming galaxies at similar redshifts .
The Ly \alpha velocity offsets show a moderate correlation with the measured star formation rate ( 2.5 \sigma ) , but no significant correlations are seen with the SFR surface density , specific SFR , stellar mass , or dynamical mass ( \lesssim 1.5 \sigma ) .
Exploring the role of dust , kinematics of the interstellar medium ( ISM ) , and geometry on the escape of Ly \alpha photons , we find no signature of selective quenching of resonantly scattered Ly \alpha photons .
However , we also find no evidence that a clumpy ISM is enhancing the Ly \alpha equivalent width .
Our results suggest that the low metallicity in LAEs may be responsible for yielding an environment with a low neutral hydrogen column density as well as less dust , easing the escape of Ly \alpha photons over that in continuum-selected star-forming galaxies .