Table 2
Effects of bar strength, disk thickness, and merger history on SFH distortions.
| Disk region | Increasing bar strength | Increasing disk thickness | Merger history effects |
|---|---|---|---|
| Innermost disk (red) 0.15-0.45 hd |
Age >9 Gyr: SFR overestimated by up to ~75%; strong bars funnel old stars inward and can quench central SF at late times. | Age >6 Gyr: SFR overestimates stronger in thicker disks, up to ~125%; reflects more centrally concentrated old pops. rather than more efficient migration. | Early massive mergers (>8 Gyr ago) drive inward migration from larger radii, producing inner-disk SFR overestimates up to ~75%. |
| Intermediate inner disk (orange) 0.75-1.05 hd |
Age >6 Gyr: SFR underestimated by up to ~30%; Age <6 Gyr: SFR overestimated by up to ~30% as bars feed this region from both sides. | Only weak dependence on thickness; the age trends are largely set by bar strength, with little variation as disks get thicker. | Early massive mergers (>8 Gyr ago) lead to SFR underestimates because stars formed here migrate both inward (to the center) and outward (to the middle disk). |
| Middle disk (green) 1.35-2.25 hd |
Age >9 Gyr: SFR overestimated by up to ~50%; Ages ~2-9 Gyr: SFR underestimated by up to ~30% as region transitions from being populated by inward-born migrators to more in situ stars. | For old populations (Age >6 Gyr), SFR can be underestimated by up to ~50% in thicker disks relative to thin disks, reflecting less efficient migration into the middle disk. | Intermediate-time mergers (4-8 Gyr ago) sustain middle-disk SFR underestimates through two-way redistribution of stars both inward and outward. |
| Outer Disk (blue) 2.55-3.45 hd |
Age >6 Gyr: SFR overestimated by up to ~150%; strong bars continuously feed the outer disk with stars migrated outward from inner radii. | Maximum SFR overestimate occurs in thin disks: up to ~160% for strongly barred and ~100% for weakly barred galaxies; the bias decreases as disks become thicker. | Early mergers (>8 Gyr) cause an overestimation of SFR by up to ~120%; late mergers (<4 Gyr) underestimate SFR by up to ~20% due to enhanced inward migration from outermost disk. |
Notes. “Age” refers to stellar age at z = 0 (equivalently, lookback time since formation). The table summarizes how bar strength, disk thickness, and merger history modify the inferred star formation histories (SFHs) in different radial regions by altering the balance between in situ star formation and radial migration-driven redistribution.
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