Assigned ID: 68 ----- Attempting Submission 1 (Tue Feb 21 20:05:51 GMT 2012) ----- We request archival student funding to complete a study on the rest-frame ultraviolet (UV) colors of galaxies at z=8, using new Cycle 19 data in the Hubble Ultra Deep Field (HUDF). The addition of these new data quadruple the exposure time in the F105W band, allowing the compilation of much more robust samples of z=8 galaxies. In addition, this program obtains data in a new filter, F140W, which will allow robust colors of z=8 galaxies to be measured. The only color of z=8 galaxies measurable with the previous data in the HUDF is F125W-F160W, which is contaminated by both the Lyman break, and Lyman alpha emission. Our previous work has examined in detail the evolution of the rest-frame UV colors of galaxies from 4 < z < 7. We found that while typical galaxies at z~7 are dust free, those at z < 6 become progressively dustier. This is consistent with a scenario where the typical high redshift galaxy does not build up its dust reservoir until low-mass AGB stars begin producing dust, which will occur at z < 7 assuming galaxies form at z ~ 15-20. Any dust formed in supernovae is lost in the low-mass galaxies due to outflows, similar to the mass-metallicity relation at lower redshift. Pushing these studies to z~8 will allow us to test this hypothesis. If z~7 galaxies are truly dust free, than z~8 galaxies should have similar colors. However, if we find z~8 galaxies to have significantly bluer colors, then it will signify that we have reached an era of very low metallicity star formation. Finally, if the massive galaxies at z~8 are also dusty, then it is further evidence that dust forms very early in the universe. COSMOLOGY 12 Small false 0.0 0.0 false false false false SUPPORTED