NEFERTITI: Linking early galaxy formation to the assembly of the Milky Way

Abstract

We use a new implementation of the NEFERTITI galaxy formation model, coupled to $\sim 30$ high-resolution Caterpillar dark-matter simulations of Milky Way (MW) analogues, to connect early galaxy formation with the MW's assembly down to $z=0$. Our locally-constrained model resolves minihaloes hosting the first PopIII stars and self-consistently tracks inhomogeneous ionization and chemical enrichment. PopIII star formation begins at $z\simeq 27$, peaks at $z\simeq 10-15$, and persists down to $z\lesssim 5$, producing PopIII systems with $M_{\ast }\sim 10-5\times 10^5{\mathrm{M}}_{\odot }$. The present-day descendants of PopIII stars span $[Fe/H]<-9$ to $[Fe/H]\approx -1$, with the most metal-poor stars typically enriched by a few (1-4) low-energy supernova progenitors. Pair-instability supernova descendants more commonly form in massive haloes ($M_{\mathrm{vir}}>10^8{\mathrm{M}}_{\odot }$), often externally enriched, reflecting the strong feedback and delayed recovery following energetic explosions. These early systems serve as building blocks for the present-day Galaxy's metal-poor component: although 90$\%$ of the total stellar mass formed in situ, the accreted component dominates at $[Fe/H]<-1$ and accounts for nearly all stars with $[Fe/H]<-3$. This accreted population is largely built by a few ($\sim 5$) massive ($M_{\ast }>10^8{\mathrm{M}}_{\odot }$) destroyed dwarfs, but lower-mass systems become increasingly important at low metallicities, with ultra-faint and classical dSph analogues contributing $\sim 25\%$ at $[Fe/H]<-3$. Our model simultaneously reproduces the properties of metal-poor MW stars and the JWST "Hebe" galaxy at $z\sim 11$, supporting its identification as a pure PopIII system. Ultimately, NEFERTITI is a key tool to interpret upcoming local and high-$z$ observations linking the near- and far-field cosmology.

20 pages, 17 figures, 2 tables. Submitted to ApJ