S20B0031abst
S20B0031
We propose for 2 nights of Keck/MOSFIRE observations to follow-up two zβΌ4.7 quiescent galaxies in UDS as part of our on-going campaign to build a sample of distant quenched/quenching galaxies. From our previous pilot runs (S17B-106 and S18B-040),(1) we have confirmed two z = 4.010 and z=3.775 galaxies, both of which break the record of the highest redshift quiescent galaxy, and (2) we have measured a stellar velocity dispersion of the z=4.010 galaxy (268Β±59 km sβ1), allowing us to perform dynamical analyses for the very first time at z=4. Interestingly, the velocity dispersion is similar to those of massive galaxies today, suggesting that the velocity dispersion does not significantly evolve over the last 12 Gyr. Building upon two papers from our previous runs (Tanaka+, Valentino+), we now propose to observe the most distant quiescent galaxy candidates from our sample in UDS at zβΌ4.7. We aim (1) to spectroscopically confirm the emergence of the first quiescent galaxies when the Universe was only 1.2Gyr old, and (2) to fully capture the Balmer break in the K-band to measure their star formation epoch and timescale, which will, combined with state-of-the-art simulations, give us new insights into key physics of very early quenching.
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