Tracing early galaxies back in time: implications for the dearth of galaxies beyond z~15

Although the James Webb Space Telescope has pushed the observational frontier to $z\sim14$, the onset of star formation in the earliest galaxies remains beyond direct reach, making the star formation histories (SFH) of observed galaxies a key tool for probing earlier epochs. We develop and validate a new SFH model based on an Ornstein-Uhlenbeck process, capable of reproducing the bursty star formation expected in high-redshift galaxies. Tested on the SPHINX$^{20}$ mock catalogs, it accurately recovers stellar masses and SFRs and reconstructs cumulative SFHs at population level; the formation redshift is well constrained at $z\gtrsim9$ but not at $z\sim8$. Applied to 400 galaxies at $9