Dr. Vicente Estrada-Carpenter

Using a forward modeling technique, we fit the stellar populations of a sample of 31 massive quiescent galaxies in the CLEAR survey, in a redshift range of 1 < z < 1.8. Our measurements indicate that massive quiescent galaxies in this redshift range have ~ solar stellar metallicities. Thus, there is no evolution in the stellar metallicity - mass relation, up to a redshift of z ~ 1.8. We also show that many of these galaxies had formed ~70% of their stellar mass by z ~ 2-3.

Combining photometric, G102 grism, and G141 grism data, we constrain the stellar populations and derive "non-parametric" star-formation histories for a sample of 97 massive quiescent galaxies in the CLEAR survey, in a redshift range of 0.8 < z < 2.5. By comparing formation redshifts (where the galaxy formed half its mass) to stellar surface mass densities within 1 kiloparsec we see that the most compact galaxies are biased to form early (z>2.5), while less compact galaxies show a wide range of formation redshifts. Our results favor a scenario where compact galaxies formed rapidly at high redshift, then go through subsequent evolution through minor mergers.

We analyzed ~400 massive galaxies at redshifts 0.8 < z < 1.65 using deep HST WFC3 grism spectra plus multiwavelength photometry from the CLEAR survey. Using flexible star-formation histories, we quantify the probability that a galaxy is quiescent and trace its structural evolution. Our key findings are: galaxies become compact during their transit through the green valley—their stellar mass surface densities rise by ~0.25 dex, while overall stellar mass actually decreases slightly (~4 %), and morphologies shift to higher Sérsic index and smaller effective radius. This indicates that structural transformation accompanies quenching

This work presents a new methodology for extracting emission-line maps from JWST/NIRISS slitless grism data—accurately modeling spatially varying continuum and line flux—to investigate star formation on ~10 Myr (via Hα) and ~100 Myr (via UV and broadband SEDs) timescales within a strongly lensed galaxy pair at z = 0.8718. The system—dubbed the “Question Mark Pair” due to its lensed morphology—includes a face-on blue disk and a dusty edge-on galaxy, together exhibiting 20 star-forming clumps: 7 bursting, 10 quenching, and 3 in equilibrium. Star formation rates decline sharply with radius (by factors of ~4.7 for Hα and ~3.8 for broadband), but the overall SFR over the past ~100 Myr increased by a factor of ~1.6, suggesting interaction-triggered activity. This pilot demonstrates the promise of spatially resolved JWST/NIRISS grism spectroscopy to unravel galaxy assembly at Cosmic Noon.

Using the forward-modeling tool Sleuth on JWST/NIRISS CANUCS grism data, we extracted high-resolution emission-line maps (Hα, [SII], [SIII]) for ~20 galaxies at redshifts 0.6-1.35. Our analysis showed that compact star-forming clumps are systematically more metal-poor—by about 0.1 dex—than their host galaxy environments, indicating metallicity dilution of roughly 20%. These clumps simultaneously exhibit elevated star formation rates, strongly supporting a scenario where inflow of metal-poor gas fuels intense localized star formation at Cosmic Noon.