arXiv subjects

Alice Mori

Publications and source records attributed to Alice Mori.

3 recordsLinked to original sources

arXiv2026

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

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 $z\simeq27$, peaks at $z\simeq10-15$, and persists down to $z\lesssim5$, producing PopIII systems with $M_*\sim10-5\times10^5\:{\rm M_\odot}$. The present-day descendants of PopIII stars span ${\rm [Fe/H]<-9}$ to ${\rm [Fe/H]\approx-1}$, 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 ($M_{\rm vir}>10^8\:{\rm M_\odot}$), 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 $[{\rm Fe/H}]<-1$ and accounts for nearly all stars with $[{\rm Fe/H}]<-3$. This accreted population is largely built by a few ($\sim5$) massive ($M_*>10^8\:{\rm M_\odot}$) destroyed dwarfs, but lower-mass systems become increasingly important at low metallicities, with ultra-faint and classical dSph analogues contributing $\sim25\%$ at $[{\rm Fe/H}]<-3$. Our model simultaneously reproduces the properties of metal-poor MW stars and the JWST "Hebe" galaxy at $z\sim11$, 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.

astro-ph.GA↗

arXiv2025

Evidence of Gaia Enceladus experiencing at least two passages around the Milky Way

One of the major recent breakthroughs has been the discovery of the last Major Merger to happen in the history of the Milky Way. Around 10 Gyr ago the galaxy Gaia Enceladus, with estimated ~10% of the Milky Way mass, fell into its potential, bringing a large amount of stars which can be identified through their unique chemical and kinematic signatures. Simulations have long predicted that a galaxy of this size should experience several passages through the disk of the Milky Way before eventually being fully dispersed. For the first time, we present observational evidence to support this. We identify two subpopulations accreted from Gaia Enceladus: 1) stars which today have large kinematic energy, which originate from the outskirts of Gaia Enceladus and were accreted during early passages; 2) stars with low kinetic energy accreted at later passages, originating from the inner parts of Gaia Enceladus. Through the use of high-precision chemical abundances, crucially including new aluminum measurements, we show that in all observed abundance ratios ([Fe/H], [Al/Fe], [Mg/Fe] and [Mg/Ba]), stars with high energy show evidence of coming from a less chemically evolved outer region of Gaia Enceladus, compared to the stars with low energy. We therefore conclude that Gaia Enceladus experienced several passages before merging with the main body of our Galaxy. This discovery has wide implications for our understanding of this event, and consolidates Gaia Enceladus as a benchmark for studying galaxy mergers and hierarchical galaxy formation in extraordinary details.

astro-ph.GA↗

arXiv2024

Metallicity distributions of halo stars: do they trace the Galactic accretion history?

The standard cosmological scenario predicts a hierarchical formation for galaxies. Many substructures were found in the Galactic halo, identified as clumps in kinematic spaces, like the energy-angular momentum one (E-Lz), under the hypothesis of the conservation of these quantities. If these clumps also feature different chemical properties, e.g. metallicity distribution functions (MDF), they are often associated to independent merger debris. The aim of this study is to explore to what extent we can couple kinematics and metallicities of stars in the Galactic halo to reconstruct the accretion history of the Milky Way. In particular, we want to understand whether different clumps in the E-Lz space with different MDF should be associated to distinct merger debris. We analysed dissipationless, self-consistent high-resolution N-body simulations of a MW-type galaxy accreting a satellite with mass ratio 1:10, with different orbital parameters and metallicity gradients (assigned a posteriori). We confirm that accreted stars from a ~1:10 satellite redistribute in a wide range of E and Lz, due to the dynamical friction, thus not being associated to a single clump. Because satellite stars with different metallicities can be deposited in different regions of the E-Lz space (on average the more metal-rich ones end up more gravitationally bound to the MW), this implies that a single ~1:10 accretion can manifest with different MDFs, in different regions of the E-Lz space. Groups of stars with different E, Lz and metallicities may be interpreted as originating from different satellites, but our analysis shows that these interpretations are not physically motivated. In fact, the coupling of kinematics with MDFs to reconstruct the accretion history of the MW can bias the reconstructed merger tree towards increasing the number of past accretions and decreasing the masses of the progenitor galaxies.

astro-ph.GA↗