Quantifying stellar radial migration in an N-body simulation: blurring, churning, and the outer regions of galaxy discs

Abstract

Radial stellar migration in galactic discs has received much attention in studies of galactic dynamics and chemical evolution, but remains a dynamical phenomenon that needs to be fully quantified. In this work, using a Tree-SPH simulation of an Sb-type disc galaxy, we quantify the effects of blurring (epicyclic excursions) and churning (change of guiding radius). We quantify migration (either blurring or churning) both in terms of flux (the number of migrators passing at a given radius), and by estimating the population of migrators at a given radius at the end of the simulation compared to non-migrators, but also by giving the distance over which the migration is effective at all radii. We confirm that the corotation of the bar is the main source of migrators by churning in a bar-dominated galaxy, its intensity being directly linked to the episode of a strong bar, in the first 1-3 Gyr of the simulation. We show that within the outer Lindblad resonance (OLR), migration is strongly dominated by churning, while blurring gains progressively more importance towards the outer disc and at later times. Most importantly, we show that the OLR limits the exchange of angular momentum, separating the disc in two distinct parts with minimal or null exchange, except in the transition zone, which is delimited by the position of the OLR at the epoch of the formation of the bar, and at the final epoch. We discuss the consequences of these findings for our understanding of the structure of the Milky Way disc. Because the Sun is situated slightly outside the OLR, we suggest that the solar vicinity may have experienced very limited churning from the inner disc.

Accepted for publication in Astronomy and Astrophysics (acceptance date: 27/04/15), 24 pages, 24 figures

References in corpus (12)

• The Atomic to Molecular Transition in Galaxies. II: HI and H_2 Column Densities
• Radial mixing and the transition between the thick and thin Galactic discs
• The Atomic to Molecular Transition in Galaxies. I: An Analytic Approximation for Photodissociation Fronts in Finite Clouds
• Tracing chemical evolution over the extent of the Milky Way's Disk with APOGEE Red Clump Stars
• Color Profiles of Spiral Galaxies: Clues on Outer-Disk Formation Scenarios
• Reconstructing the star formation history of the Milky Way disc(s) from chemical abundances
• The effect of radial migration on galactic disks
• New Constraints on the Galactic Bar
• Mapping a stellar disk into a boxy bulge: The outside-in part of the Milky Way bulge formation
• The Structure and Stellar Content of the Outer Disks of Galaxies: A New View from the Pan-STARRS1 Medium Deep Survey
• Constraints on Radial Migration in Spiral Galaxies I. Analytic Criterion for Capture at Corotation
• The Milky Way as a High Redshift Galaxy: The Importance of Thick Disk Formation in Galaxies

Cited by in corpus (6)

• Revisiting long-standing puzzles of the Milky Way: the Sun and its vicinity as typical outer disk chemical evolution
• Prospects for chemically tagging stars in the Galaxy
• What the Milky Way bulge reveals about the initial metallicity gradients in the disc
• The continuous rise of bulges out of galactic disks
• The Impact of Stellar Migration on Disk Outskirts
• The Radial Distribution of Mono-Metallicity Populations in the Galactic Disk as Evidence for Two-Phase Disk Formation