16506

We propose to acquire HST-WFC3 imaging of two galaxies at zvirgul7 recently detected by ALMA in CORCHETE_OPENCIICORCHETE_CLOSE 158 micron and CORCHETE_OPENOIIICORCHETE_CLOSE 88 micron emission at high angular resolution. The CORCHETE_OPENOIIICORCHETE_CLOSE emission comma corresponding to diffuse comma highly-ionized gas comma and CORCHETE_OPENCIICORCHETE_CLOSE emission comma tracing neutral gas comma allow some of the first explorations of the interstellar medium in the Epoch of Reionization (EoR). Combined comma they suggest we are witnessing intense star formation which locally shows extreme CORCHETE_OPENOIIICORCHETE_CLOSE-CORCHETE_OPENCIICORCHETE_CLOSE luminosity ratios that are indicative of .leaking. ionizing radiation and hence may be of great importance to Reionization. Other regions in these galaxies comma however comma might be more metal-enriched and obscured by dust comma as indicated by ALMA measurements of the dust continuum. To conclusively shed light on the key processes affecting star formation in the EoR comma we propose to obtain deep HST images of the rest-frame UV (both a virgul5x improvement in limiting flux and angular resolution over existing comma ground-based imaging). We will measure accurate sizes of star-forming clumps on sub-kiloparsec scales comma study possible ongoing mergers comma and compare the UV morphology with spatially resolved maps of dust continuum and physical parameters such as the ionization parameter extracted from the CORCHETE_OPENCIICORCHETE_CLOSE and CORCHETE_OPENOIIICORCHETE_CLOSE observations. These comparisons will give insight into the physical conditions of both UV-bright star-forming clumps and dust-obscured star-forming regions. Combined with a larger sample including three other galaxies comma this data will paint a physically motivated picture of star formation in the EoR in time for science exploration with JWST.