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

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.

19 pages, 15 figures, Accepted 6 January 2026, A&A

References in corpus (37)

• The Transiting Exoplanet Survey Satellite
• Cosmic Star Formation History
• The K2 Mission: Characterization and Early results
• Streams, substructures and the early history of the Milky Way
• On the Formation of Galactic Thick Disks
• Reconstructing the star formation history of the Milky Way disc(s) from chemical abundances
• The Star Formation Histories of Local Group Dwarf Galaxies II. Searching For Signatures of Reionization
• Observations of Thick Disks in the Hubble Space Telescope Ultra Deep Field
• Gaia Data Release 3: Mapping the asymmetric disc of the Milky Way
• The effect of radial migration on galactic disks
• Bar quenching in gas-rich galaxies
• Chemical Enrichment and Radial Migration in the Galactic Disk -- the origin of the [$\alpha /\mathrm{Fe}]$ Double Sequence
• Keeping it Cool: Much Orbit Migration, yet Little Heating, in the Galactic Disk
• Fluctuations in galactic bar parameters due to bar-spiral interaction
• The Rich Are Different: Evidence from the RAVE Survey for Stellar Radial Migration
• Unveiling the time evolution of chemical abundances across the Milky Way disk with APOGEE
• The merger and assembly histories of Milky Way- and M31-like galaxies with TNG50: disk survival through mergers
• On the origin of the Galactic thin and thick discs, their abundance gradients and the diagnostic potential of their abundance ratios
• Chronology of our Galaxy from Gaia Colour-Magnitude Diagram-fitting (ChronoGal). I. The formation and evolution of the thin disk from the Gaia Catalogue of Nearby Stars
• Galaxy Zoo: Kinematics of strongly and weakly barred galaxies
• Digging into the Galactic Bulge: stellar population and structure of the poorly studied cluster NGC 6316
• Exponential Disks from Stellar Scattering: III. Stochastic Models
• Observational Constraints of Radial Migration in the Galactic Disc Driven by the Slowing Bar
• Pattern speed evolution of barred galaxies in TNG50
• Stellar scattering and the formation of exponential discs in self-gravitating systems
• Determining the Timescale over Which Stellar Feedback Drives Turbulence in the ISM: A Study of four Nearby Dwarf Irregular Galaxies
• Stellar migration in the Auriga simulations
• Empirical derivation of the metallicity evolution with time and radius using TNG50 Milky Way/Andromeda analogues
• Evolution of the radial ISM metallicity gradient in the Milky Way disk since redshift $\approx 3$
• Chronology of our Galaxy from Gaia colour-magnitude diagram fitting (ChronoGal) II. Unveiling the formation and evolution of the kinematically selected Thick and Thin Discs
• Rediscovering the Milky Way with orbit superposition approach and APOGEE data I. Method validation
• An observational testbed for cosmological zoom-in simulations: constraining stellar migration in the solar cylinder using asteroseismology
• Bar-spiral interaction produces radial migration and star formation bursts
• Investigating the role of bars in quenching star formation using spatially resolved UV-optical colour maps
• Probing the origins. I. Generalised Additive Model inference of birth radii for Milky Way stars in the solar vicinity
• Rediscovering the Milky Way with an orbit superposition approach and APOGEE data V. The disc growth and history of star formation
• The impact of radial migration on disk galaxy star formation histories I. Biases in spatially resolved estimates