Discovery of the most distant star-forming and quenched galaxies in the universe

While the high-redshift component of the CANDELS survey was designed with the z ∼ 6-8 era in mind, these data do probe the far-UV of galaxies at even higher redshift. A few studies have ventured this far out, and have published conflicting results - some continue to find significant star-formation, while others conclude there is a steep decline in this quantity. Here I report on a new search for z = 9-10 galaxies, making significant use of the Spitzer/IRAC data in the CANDELS fields. We have discovered a larger number of galaxies in this epoch than previous works, implying the UV luminosity function, and thus the SFR density, may not evolve as steeply as previously thought. This implies that star-formation begins early in the universe. I will also report on a new study searching for the earliest quenched galaxies at 3 < z < 5, which are not predicted by models, yet may exist if galaxies form very early, and thus can approach their quenching phase quicker.