The impact of radial migration on disk galaxy star formation histories II. Role of bar strength, disk thickness, and merger history

Bernaldez, JP, Minchev, I, Ratcliffe, B, Marques, L, Sysoliatina, K, Walcher, J, Khoperskov, S, Martig, M ORCID: 0000-0001-5454-1492, de Jong, RS and Steinmetz, M (2026) The impact of radial migration on disk galaxy star formation histories II. Role of bar strength, disk thickness, and merger history. Astronomy and Astrophysics, 707. ISSN 0004-6361

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Abstract

Reconstructing the star formation history (SFH) of disk galaxies is central to understanding their growth and evolution, yet such estimates can be strongly biased by stellar radial migration over cosmic time. Using 186 Milky Way (MW) and Andromeda (M31) analogs from the TNG50 cosmological simulation, we compare star formation rates (SFRs) inferred from present-day stellar positions with those based on stellar birth radii to quantify the magnitude, spatial structure, and temporal evolution of migration-induced biases. We find that radial migration systematically produces artificial star formation in regions that had not yet formed stars. Notably, ~80% of galaxies exhibit outer-disk stars older than 10 Gyr, which we find to have formed at radii interior to the outer disk and to have reached their present locations via substantial outward migration. Similar effects appear in ~45% of galaxies at intermediate radii during early epochs, and in 30% of quenched inner disks within the past 4 Gyr. Migration also smooths SFHs, washing out localized bursts and suppressions by dispersing stars across neighboring radii. The strength and imprint of these distortions depend sensitively on galactic structure and evolutionary history: strong bars drive mean SFR overestimates of up to 75% in the inner disk and 150% in the outskirts; thinner, dynamically cold disks suffer average outer-disk biases up to 160%; while thick disks exhibit typical inner-disk biases up to 125%. Merger timing further modulates these patterns. Our results demonstrate that failing to account for stellar migration can lead to severe misinterpretations of when and where stars formed, with direct implications for the chemical and evolutionary histories of the MW and external galaxies.

Item Type:	Article
Uncontrolled Keywords:	5101 Astronomical Sciences; 51 Physical Sciences; 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:	EDP Sciences
Date of acceptance:	6 January 2026
Date of first compliant Open Access:	22 September 2026
Date Deposited:	22 Sep 2026 13:33
Last Modified:	22 Sep 2026 13:33
DOI or ID number:	10.1051/0004-6361/202557002
URI:	https://researchonline.ljmu.ac.uk/id/eprint/29507

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