16734

The escape fraction of ionizing radiation (f_esc) comma a fundamental parameter in modeling of reionization comma is impossible to measure at z>6. Therefore comma a number of HST studies are calibrating indirect indicators of f_esc comma using large samples of local galaxies (zvirgul0.3). What is missing is a comparable sample of galaxies at the highest redshifts where all the necessary observables (covering the full spectrum from 950AA to the rest frame optical) can be measured. We propose a coordinated HST-NOIRLab program to observe a unique sample of 8 strongly lensed Lyman alpha (Lya) emitters at 2.1<z<2.6. THese observations will enable the measurement of their escape fraction of ionizing radiation and test for evolution in its indirect estimators. WFC3 UVIS imaging will directly measure the emission at ionizing wavelengths (LyC comma lambda<912AA). Longer wavelength imaging will constrain the properties of the young stars comma including the dust content and the sizes of the star-forming regions. The coordinated NOIRLab Gemini observations comma consisting of rest-frame UV+optical IFU spectroscopy comma will provide the diagnostics required to quantify the intrinsic ionizing radiation field comma nebular dust content comma and kinematics of the ISM. Only the combination of the strong magnification and redshifts of these galaxies allow us to perform these measurements comma probing a completely unexplored regime of physical sizes (virgul100svirgulpc) and intrinsic luminosities (virgul1-1000 L*UV) at z>0.5. Our sample complement planned JWST programs that are targeting the rest-frame optical for known zvirgul3 bright emitters.