| Speaker: | Akash Vani (Max Planck Institute for Astrophysics) |
|---|---|
| Title: | Grow fast, die young: The early universe’s galaxy formation recipe |
| Date (JST): | Tue, Jul 14, 2026, 11:00 - 12:00 |
| Place: | Seminar Room A |
| Abstract: |
Recent observations have revealed abundant populations of massive, UV-bright, compact, and, in some cases, already quenched galaxies within the first few billion years of cosmic history. In this work, we develop a new semi-analytic framework for modelling galaxy formation and evolution by extending the L-Galaxies model on top of the Gadget-4 code base. This framework is designed to investigate the physical processes that regulate early star formation, structural transformation, and quenching across the entire redshift range. We introduce a gas-density-based star formation efficiency prescription, a regulated stellar feedback model in which the effective coupling of supernova and stellar-wind energy depends on ISM density conditions, an updated disc-instability treatment that self-consistently links gas inflow and star formation across radial rings, and a galaxy merger model that incorporates gas dissipation through an energy-conservation formalism. To calibrate the model, we develop a new parallelised, fast, and efficient MCMC framework that simultaneously constrains parameters using stellar mass functions and quenched fractions over z≃0-4, as well as ultraviolet luminosity functions at z≃11,12. Through dimensionality reduction, parallelisation, and code optimisation, this calibration framework achieves a significant speed-up. We find that combining density-dependent star formation with regulated stellar feedback enables rapid assembly of stellar mass in the early universe, while still matching low-redshift observations. During mergers, gas dissipation leads to more compact remnants in gas-rich systems, aligning better with the observed compact sizes of high-redshift galaxies. Additionally, we observe that halos are more efficient at high redshift compared to low redshift. While the model also generates a variety of disk- and bulge-dominated galaxies at low redshift, it tends to overproduce disks at earlier times. |
