Stellar Population Properties of Massive Quiescent Galaxies Derived from Deep Hubble Space Telescope Grism Data
| Main Author: | Vicente Estrada-Carpenter |
|---|---|
| Format: | info Proceeding Journal |
| Terbitan: |
, 2019
|
| Online Access: |
https://zenodo.org/record/3556797 |
Daftar Isi:
- Galaxies show strong correlations among their stellar masses, morphologies, and formation histories. The origin of these correlations are difficult to define, primarily due to the uncertainties in measured star-formation histories being ~ logarithmic in time. Star-formation histories are therefore better constrained closer to their formation and quenching epochs, at high redshifts. Here we use ``non-parametric'' star-formation histories to derive the formation and quenching timescales of quiescent galaxies at 0.7 < z < 2.5. We model deep HST grism spectroscopy and photometry from the CLEAR (CANDELS Lyman-\(\alpha\) Emission at Reionization) survey, using a nested sampling method to derive constraints on stellar population parameters and star-formation histories. The galaxy formation redshifts (defined as the point where they had formed 50% of their stellar mass) range from z50 ~ 2 (shortly prior to the observations) up to z50 > 5, at the earliest possible times. Furthermore, the formation redshifts are tied to the galaxies' morphology. Galaxies with the highest stellar-mass surface densities (\(\log \Sigma_1 / (M_\odot\ \mathrm{kpc}^{-2}) \) >10.2 where \(\Sigma_1\) is the stellar mass within 1~kpc-comoving), exclusively favor early formation, with z50 > 3. In other words, the most compact quiescent galaxies all formed at the earliest periods in cosmic history. Galaxies with lower surface density (\(\log \Sigma_1 / (M_\odot\ \mathrm{kpc}^{-2}) \) = 9.5 - 10.2) show a wide range of formation epochs (z50 ~ 1.5 - 8) and these galaxies likely experience a range of formation and assembly histories. We argue that the surface density threshold \(\log \Sigma_1 / (M_\odot\ \mathrm{kpc}^{-2}) \) > 10.2 uniquely identifies galaxies that formed in the earliest cosmic times, and we discuss the implications this has for galaxy formation models.