Work

Investigating the star formation histories of galaxies from cosmic dawn to the Epoch of Reionization with the Santa Cruz SAM

Year: 2026

Type: article

Abstract: ABSTRACT The James Webb Space Telescope (JWST) has opened a new window on to galaxy evolution in the very early Universe. In this work, we leverage halo merger trees extracted from the gureft dark-matter-only cosmological simulation suite together with the Santa Cruz semi-analytic model (SAM) for galaxy formation to investigate the predicted star formation histories (SFHs) of galaxies from cosmic dawn ($z\sim 14$) to the end of the Epoch of Reionization (EoR; $z\sim 6$). While we find that on average, median SFHs of galaxies across all masses are uniformly and rapidly rising over time from $14 \lesssim z \lesssim 6$ as expected, individual galaxy SFHs show a range of diverse SFHs, even for a fixed terminal mass or redshift, with bursts and mini-quenching episodes in agreement with SFHs inferred from observations. The median lookback time to form the youngest 50 per cent ($t_{50}$) and 90 per cent ($t_{90}$) of galaxies’ stars decreases weakly with increasing stellar mass, and strongly with the redshift of observation. For galaxies at $z\gtrsim 12$, we find typical values of $t_{50}\lesssim 30$ Myr and $t_{90}\lesssim 70$ Myr, a factor of $\sim$3–4 shorter than for comparable galaxies near the end of EoR ($z\sim 6$). The young-star dominated nature of stellar populations in ultra-high-z galaxies implies that careful modelling of young stellar populations is crucial for obtaining accurate synthetic photometry. In addition, our results have important implications for interpreting observational indicators of SFHs and time-scales.

Source: Monthly Notices of the Royal Astronomical Society

DOI: 10.1093/mnras/stag1913

Authors: L Y Aaron Yung, Rachel S Somerville, Steven L Finkelstein, Kartheik G Iyer

Institutions: Space Telescope Science Institute, Flatiron Institute, The University of Texas at Austin

Language: English

Topic: Galaxies: Formation, Evolution, Phenomena

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $3,046