Stellar Populations and Formation Histories of Massive Galaxies Derived from Deep Hubble Space Telescope Grism Data

A key question in the field of galaxy evolution is: How do massive quiescent galaxies form in the early universe? Many works have shown the existence of massive quiescent galaxies up to redshifts of z>3 (when the age of the universe was < 2.2 Gyr). These galaxies are puzzling because they have been able to form massive amounts of stellar mass (log(M/M) > 10) in a relatively rapid fashion, even simulations have struggled to recreate these galaxies. Therefore we are lacking some knowledge about the formation of massive galaxies. My research has focused on understanding the star-formation, chemical, morphological, and quenching histories of high redshift (0.7<z<2.5) massive galaxies usingHSTWFC3 grism spectra + photometry from the CLEAR (CANDELS Lyman-α Emission at Reionization) survey. Utilizing the data from the CLEAR survey has allowed me to study large samples (∼100) of spectra from massive galaxies, something not currently possible from ground-based surveys. By studying these massive galaxies at high redshift we can better constrain their star-formation histories as the uncertainty on the timescales(and therefore the ages) of stars and stellar populations are quasi-logarithmic. My work has touched upon topics such as the mass - stellar metallicity relationship (showing that this relationship does not evolve with redshift up a z = 1.7), the link between a galaxies formation redshift, and its morphology (providing evidence that the most compact galaxies get their compact morphologies from having formed in the early universe), and the evolution of galaxies as they cross the green valley (showing that galaxies form more rapidly at high redshift and that fast quenching occurs more in high mass galaxies).These works have begun to outline how massive quiescent galaxies in the early universe formed.