GalactiKit: Reconstructing mergers from z = 0 debris using simulation-based inference in Auriga

Sante, A ORCID: 0009-0005-1823-8089, Kawata, D ORCID: 0000-0001-8993-101X, Font, AS ORCID: 0000-0001-8405-9883 and Grand, RJJ ORCID: 0000-0001-9667-1340 (2025) GalactiKit: Reconstructing mergers from z = 0 debris using simulation-based inference in Auriga. Monthly Notices of the Royal Astronomical Society, 542 (3). pp. 1776-1790. ISSN 0035-8711

Preview

Text GalactiKit reconstructing mergers from z = 0 debris using simulation-based inference in Auriga.pdf - Published Version Available under License Creative Commons Attribution. Download (3MB) | Preview

Abstract

We present GalactiKit, a data-driven methodology for estimating the lookback infall time, stellar mass, halo mass, and mass ratio of the disrupted progenitors of Milky Way-like galaxies at the time of infall. GalactiKit uses simulation-based inference to extract the information on galaxy formation processes encoded in the Auriga cosmological magnetohydrodynamic (MHD) simulations of Milky Way-mass haloes to create a model that relates the properties of mergers to those of the corresponding merger debris at z = 0. We investigate how well GalactiKit can reconstruct the merger properties given the dynamical, chemical, and the combined chemodynamical information of debris. For this purpose, three models were implemented considering the following properties of merger debris: (a) total energy and angular momentum, (b) iron-to-hydrogen and alpha-to-iron abundance ratios, and (c) a combination of all of these. We find that the kinematics of the debris can be used to trace the lookback time at which the progenitor was first accreted into the main halo. However, chemical information is necessary for inferring the stellar and halo masses of the progenitors. In both models (b) and (c), the stellar masses are predicted more accurately than the halo masses, which could be related to the scatter in the stellar mass-halo mass relation. Model (c) provides the most accurate predictions for the merger parameters, which suggests that combining chemical and dynamical data of debris can significantly improve the reconstruction of the Milky Way's assembly history.

Item Type:	Article
Uncontrolled Keywords:	5101 Astronomical Sciences; 51 Physical Sciences; Stem Cell Research; 0201 Astronomical and Space Sciences; Astronomy & Astrophysics; 5101 Astronomical sciences; 5107 Particle and high energy physics; 5109 Space sciences
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	Oxford University Press (OUP)
Date of acceptance:	12 August 2025
Date of first compliant Open Access:	8 January 2026
Date Deposited:	08 Jan 2026 15:46
Last Modified:	08 Jan 2026 15:46
DOI or ID number:	10.1093/mnras/staf1343
URI:	https://researchonline.ljmu.ac.uk/id/eprint/27823

View Item