The imprint of radial migration on the vertical structure of galaxy disks

Abstract

We use numerical simulations to examine the effects of radial migration on the vertical structure of galaxy disks. The simulations follow three exponential disks of different mass but similar circular velocity, radial scalelength, and (constant) scale height. The disks develop different non-axisymmetric patterns, ranging from feeble, long-lived multiple arms to strong, rapidly-evolving few-armed spirals. These fluctuations induce radial migration through secular changes in the angular momentum of disk particles, mixing the disk radially and blurring pre-existing gradients. Migration affects primarily stars with small vertical excursions, regardless of spiral pattern. This "provenance bias" largely determines the vertical structure of migrating stars: inward migrators thin down as they move in, whereas outward migrators do not thicken up but rather preserve the disk scale height at destination. Migrators of equal birth radius thus develop a strong scale-height gradient, not by flaring out as commonly assumed, but by thinning down as they spread inward. Similar gradients have been observed for low-[$\alpha$/Fe] mono-abundance populations (MAPs) in the Galaxy but our results argue against interpreting them as a consequence of radial migration. This is because outward migration does not lead to thickening, implying that the maximum scale height of any population should reflect its value at birth. In contrast, Galactic MAPs have scale heights that increase monotonically outwards, reaching values that greatly exceed those at their presumed birth radii. Given the strong vertical bias affecting migration, a proper assessment of the importance of radial migration in the Galaxy should take carefully into account the strong radial dependence of the scale heights of the various stellar populations.

8 pages, 6 figures, submitted to ApJ

References in corpus (9)

• Riding the Spiral Waves: Implications of Stellar Migration for the Properties of Galactic Disks
• The Milky Way's circular velocity curve between 4 and 14 kpc from APOGEE data
• Radial mixing and the transition between the thick and thin Galactic discs
• Color Profiles of Spiral Galaxies: Clues on Outer-Disk Formation Scenarios
• On the Formation of Galactic Thick Disks
• The effect of radial migration on galactic disks
• Quantifying stellar radial migration in an N-body simulation: blurring, churning, and the outer regions of galaxy discs
• Impacts of a Flaring Star-forming Disc and Stellar Radial Mixing on the Vertical Metallicity Gradient
• Revealing the spiral arms through radial migration and the shape of the Metallicity Distribution Function

Cited by in corpus (22)

• Keeping it Cool: Much Orbit Migration, yet Little Heating, in the Galactic Disk
• The GALAH Survey: Chemodynamics of the Solar Neighbourhood
• The reports of thick discs' deaths are greatly exaggerated: thick discs are NOT artefacts caused by diffuse scattered light
• Thick Disks in the Hubble Space Telescope Frontier Fields
• Radial migration in a stellar galactic disc with thick components
• Constraints on Radial Migration in Spiral Galaxies - II. Angular momentum distribution and preferential migration
• The innate origin of radial and vertical gradients in a simulated galaxy disc
• The Flattening Metallicity Gradient in the Milky Way's Thin Disk
• Migration in the shearing sheet and estimates for young open cluster migration
• Migration and kinematics in growing disc galaxies with thin and thick discs
• On the effects of the Initial Mass Function on Galactic chemical enrichment
• Galactic disc profiles and a universal angular momentum distribution from statistical physics
• A-type stars in the Canada-France Imaging Survey II. Tracing the height of the disc at large distances with Blue Stragglers
• Radial migration and vertical action in N-body simulations
• When Cold Radial Migration is Hot: Constraints from Resonant Overlap
• Stellar scattering and the formation of exponential discs in self-gravitating systems
• Chemo-Dynamical Clustering applied to APOGEE data: Re-Discovering Globular Clusters
• The Non-Axisymmetric Influence: Radius and Angle-Dependent Trends in a Barred Galaxy
• Disk flaring with TNG50: diversity across Milky Way and M31 analogs
• Insights into the Formation and Evolution History of the Galactic Disk System
• Orbits and action changes during star-clump encounters responsible for the origin of exponential discs in dwarf galaxies
• Tidally-induced radial migration waves in LMC-like galaxies