Work

EDGE-INFERNO: The chemical signatures of assembly history in reionization fossils

Year: 2026

Type: article

Abstract: Elemental abundances preserve a fossil record of the chemical environments in which stars form. In galaxies, stellar populations represent a superposition of both in situ and accreted components, tracing internal chemical evolution as well as the histories of merged satellites. In this work, we investigate how assembly history shapes the chemical properties of present-day stellar populations in low-mass dwarf galaxies. We analyzed a suite of star-by-star cosmological zoom-in simulations of galaxies with a present-day halo mass sim1.4 _⊙. By applying the genetic modification technique to systematically vary galaxy growth while preserving the present-day halo mass, our simulations span a continuum of assembly histories, with the single-progenitor and multi-progenitor regimes representing its two limiting cases. Early-forming systems form most of their stars in a single progenitor, with centrally concentrated star formation and a continuous enrichment history. In contrast, our late-forming systems assemble by accretion of multiple progenitors with their own stellar populations, resulting in fragmented star formation across several halos with independent chemical evolution tracks. These regimes produce qualitatively different chemical signatures: single-progenitor systems exhibit connected, well-defined trends in abundance space, while multi-progenitor systems show multiple, distinct stellar populations with limited overlap. We find that metallicity distribution functions provide initial constraints on assembly history for samples of at least 50-100 member stars, but additional chemical dimensions are often required to disentangle overlapping populations. Multielement abundance analysis significantly improves the recovery of distinct components, although robust reconstruction still requires larger samples compared to metallicity distributions. Fully separating in situ and accreted populations using abundances alone remains challenging. This likely requires kinematic information. Accreted stars can contribute substantially even at high metallicities in multi-progenitor systems, while external enrichment can cause accreted material to follow similar chemical trends as in situ stars, particularly in the single-progenitor regime. These results highlight the importance of combining chemical and dynamical information when interpreting stellar populations in dwarf galaxies. edge-inferno ̊m M

Source: Astronomy and Astrophysics

DOI: 10.1051/0004-6361/202661974