Chemodynamical properties of gas-rich galaxies: A comparison of observations and simulations

¹ Institute of Astronomy, Kharkiv National University, Svobody Sq. 4, Kharkiv 61022, Ukraine
² Department of Astronomy, University of Geneva, Chemin Pegasi 51, 1290 Versoix, Switzerland
³ Institute of Physics, Laboratory of Astrophysics, École Polytechnique Fédérale de Lausanne (EPFL), 1290 Sauverny, Switzerland
⁴ European Southern Observatory, Karl-Schwarzschild Str. 2, 85748 Garching bei München, Germany
⁵ European Southern Observatory, Alonso de Córdova 3107, Casilla, 19001 Vitacura, Santiago, Chile
⁶ French-Chilean Laboratory for Astronomy, IRL 3386, CNRS and U. de Chile, Casilla 36-D, Santiago, Chile
⁷ Centre de Recherche Astrophysique de Lyon, Univ. Claude Bernard Lyon 1, 9 Av. Charles André, 69230 Saint-Genis-Laval, France
⁸ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85748 Garching b. München, Germany

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Received: 13 June 2025
Accepted: 3 February 2026

Abstract

We performed a comprehensive analysis of the chemical and dynamical properties of quasar-damped Lyman-α (DLA) galaxies and compare these to the GEAR chemodynamical simulations. Specifically, we aim to constrain the behavior of α-element enhancements with metallicity, the dependence of [α/Fe] on the specific star formation rate (sSFR), and the absorption-line velocity widths (Δv₉₀) versus stellar mass, Δv₉₀ versus metallicity, and mass–metallicity relations. For the comparison, we selected five galaxies simulated with the chemodynamical Tree-SPH code GEAR with stellar masses in the range of 6.1 ≤ log M_★/M_⊙ ≤ 10.8 and at six different redshifts between 0.33 and 4.12. We find that the abundance ratios [α/Fe] and [M/H] observed in the interstellar medium (ISM) of DLA galaxies overlap with the abundance trends in gas of the simulated galaxies. Our findings corroborate a picture in which DLAs with Δv₉₀ below and above 100 km s⁻¹ trace galaxies with masses in the ranges of 6 < log M_★ < 8 and 8 < log M_★ < 11, respectively. We suggest that observations should be used with caution when constraining the theoretical [α/Fe] versus sSFR relations because of systematics (if abundances are obtained from emission lines) or differences in the gas properties as probed by a DLA and its counterpart. So far, only the observations in absorption of inner gas of the LMC and SMC are in agreement with the simulated data. We confirm that DLAs detected at large impact parameters most likely probe the gas of satellite or other halo galaxies which are adjacent to the central galaxy. We further find that the velocity widths versus stellar masses and mass–metallicity relations agree well with observations, while GEAR should be calibrated more carefully to reproduce the Δv₉₀ versus metallicity relation. To place our results in context, we additionally incorporated chemodynamical properties of a few selected model galaxies obtained from other simulations.