The Final UV Frontier: Legacy Near-UV Imaging of the Frontier Fields

The Hubble Frontier Fields (HFFs) are proving to be as scientifically interesting at z < 3.5, as at z>7, the epoch for which it was designed. In Cycle 21, we observed three HFFs with WFC3/UVIS near-UV (NUV) imaging (8 orbits each of F275W, F336W). Here we propose to image the remaining three fields (which offer higher magnification at z<1.5) to enable the following:

The high magnification provided by gravitational lensing enables study of star formation (SF) in dwarf galaxies at 0.750.03 M_sun/yr, we can study the burstiness of SF (by comparing to grism Halpha), the UV spectral slopes and extinction curves, and the sizes and luminosities of SF clumps on scales <100 pc.

The NUV identifies the Lyman break of dwarf galaxies at 1.50.02 M_sun/yr) not available with existing data sets. We will characterize galaxies transitioning between the blue cloud and red sequence, including "jellyfish" galaxies with SF tails of stripped gas, and ellipticals and S0s with residual SF only apparent in the UV. Completing the sample will provide insight into how cluster mass and dynamical state affect quenching of cluster galaxies.