arXiv subjects

Lapo Querci

Publications and source records attributed to Lapo Querci.

3 recordsLinked to original sources

arXiv2026

CRIMSONS: An Online Tool for Modeling Chemical Enrichment with Stochastic IMF Sampling

Chemical enrichment is a universal process shaped by several interconnected factors, including stellar feedback, the nature of chemical polluters, and the underlying distribution of stellar masses. Three key ingredients are often difficult to treat simultaneously in chemical-evolution models: the stochastic sampling of the stellar IMF, uncertainties in stellar nucleosynthesis yields, and pre-enrichment from primordial PopIII stars. In low star-formation rate environments, incomplete IMF sampling makes enrichment sensitive to the random presence or absence of massive supernova progenitors. Here, we present CRIMSONS, the first online tool designed to model chemical enrichment while self-consistently incorporating these three ingredients. The framework allows users to explore different IMFs, stellar population masses and metallicities, and multiple stellar yield sets. It follows the evolution of individual stars and tracks 30 elements(H-Zn), including contributions from SN, AGB stars, and TypeIa SNe. The current implementation adopts a closed-box framework, neglecting gas flows and spatial mixing, thus providing a controlled setup to isolate the effects of IMF sampling, stellar yields, and PopIII pre-enrichment. With CRIMSONS, we show that incomplete IMF sampling produces large abundance scatter, particularly in low-mass stellar populations. Different yield prescriptions introduce element-dependent variations, while some abundance ratios remain comparatively robust across models. Finally, comparison between models including primordial enrichment and those adopting only a metallicity floor shows that PopIII pre-enrichment can significantly affect subsequent chemical evolution. CRIMSONS therefore provides a controlled framework for quantifying the relative impact of stochastic IMF sampling, nucleosynthetic uncertainties, and primordial pre-enrichment on predicted abundance patterns

astro-ph.GA↗

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

Stellar halos tracing the assembly of ultra-faint dwarf galaxies

[Abridged]Ultra-faint dwarfs (UFDs) are expected to be the relics of the earliest galaxies forming in the Universe. Observations show the presence of a stellar halo around them, which can give precious insights into the evolution of UFDs. This work investigates how merger properties impact the formation of stellar halos around UFDs, focusing on Tucana II, the most promising UFD assembled through mergers. We develop N-body simulations of isolated mergers between two UFDs with $1M_\odot$ stellar resolution. We build a suite of simulations by varying: i) the merger mass ratio, $M_1/M_2$, the specific ii) kinetic energy, $k$, and iii) angular momentum, $l$, iv) the dark-to-stellar mass ratio, $M_{DM}/M_*$, of the progenitors and iv) their stellar size, $R_{1/2}$. We use a neural network to explore the parameter space, emulating the properties of the "post-merger" UFD by quantifying the half-mass radius ($R_*$) and the fraction of stars at radii $>5R_*$ ($f_5$). Our principal component analysis clearly shows that $f_5$ ($R_*$) is primarily determined by $M_1/M_2$ ($R_{1/2}$), with $R_{1/2}$ ($M_1/M_2$) playing a secondary role. Both $f_5$ and $R_*$ show almost no dependence on $k$, $l$, and $M_{DM}/M_*$ in the explored range. Using our emulator, we find that to form the stellar halo observed in Tucana II, i.e. $f_5=10\pm5\%$ and $R_*=120\pm30$pc, we need $M_1/M_2=8_{-3}^{+4}$ and $R_{1/2}=97^{+25}_{-18}$pc. Such findings are corroborated by the consistency ($χ^2=0.5-2$) between the stellar density profile observed and those of simulations having $M_1/M_2$ and $R_{1/2}$ close to the emulator's predictions. Ongoing and planned spectroscopic surveys will greatly increase the statistics of observed stars and thus stellar halos in UFDs. By interpreting such observations with our model, we will provide new insights into the assembly history of UFDs and thus on the early galaxy formation process.

astro-ph.GA↗