Keeping It Cool: Much Orbit Migration, yet Little Heating, in the Galactic Disk

Neige Frankel, Jason Sanders, Yuan Sen Ting, Hans Walter Rix

    Research output: Contribution to journalArticlepeer-review

    66 Citations (Scopus)

    Abstract

    A star in the Milky Way's disk can now be at a Galactocentric radius quite distant from its birth radius for two reasons: either its orbit has become eccentric through radial heating, which increases its radial action J R ("blurring"), or merely its angular momentum L z has changed and thereby its guiding radius ("churning"). We know that radial orbit migration is strong in the Galactic low-α disk and set out to quantify the relative importance of these two effects, by devising and applying a parameterized model () for the distribution in the stellar disk. This model describes the orbit evolution for stars of age τ and metallicity, presuming that coeval stars were initially born on (near-)circular orbits, and with a unique at a given birth angular momentum and age. We fit this model to APOGEE red clump stars, accounting for the complex selection function of the survey. The best-fit model implies changes of angular momentum of and changes of radial action as at 8 kpc. This suggests that the secular orbit evolution of the disk is dominated by diffusion in angular momentum, with radial heating being an order of magnitude lower.

    Original languageEnglish
    Article number15
    JournalAstrophysical Journal
    Volume896
    Issue number1
    DOIs
    Publication statusPublished - 10 Jun 2020

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