Yurina Nakazato (CCA - Flatiron Institute) - Unveiling ISM Physics in High-Redshift Galaxies: Bridging Cosmological Zoom-in Simulations with JWST/ALMA Observations

The unprecedented sensitivity and resolution of JWST and ALMA have opened a new window onto galaxy formation in the first billion years of cosmic history. At z > 6, we observe diverse galaxy morphologies, spatially inhomogeneous ISM, and most strikingly, an overabundance of UV-bright galaxies extending to z > 10. I present theoretical insights into these observations using the FirstLight cosmological zoom-in simulations.
For massive galaxies (Ms >~ 1e9 Msun) at z = 6–9, we model HII regions for each stellar particle and calculate [OIII] emission using the radiative transfer code CLOUDY. High-redshift galaxies show roughly 5–10× stronger [OIII] emission than local star-forming galaxies at the same SFR, driven by high ionization parameters from young stellar populations. We derive emission line diagrams using rest-frame optical and far-infrared line ratios accessible with JWST and ALMA (e.g., [OIII]88um/5007Å), showing these diagnostics can probe multi-phase HII regions. We also present spatially resolved dust attenuation curves, revealing systematic differences between clumps and diffuse regions.
Time permitting, I will then address the overabundance of UV-bright galaxies at z > 10 through high star formation efficiencies in FirstLight and an analytical dusty outflow scenario, and outline ongoing JWST/ALMA observational collaborations and future multi-wavelength studies.

Special guest talk Wednesday, June 17 from 12:00-1:00 PM in LGRT 533. All members of the FCAD community are welcome to attend.