SIMBAD references

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 (p_m) for the distribution p(L_z,J_R,τ,[Fe/H]| p_m) in the stellar disk. This model describes the orbit evolution for stars of age τ and metallicity [Fe/H], presuming that coeval stars were initially born on (near-)circular orbits, and with a unique [Fe/H] 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 sqrt(<)ΔL_z>²~619kpckms^–1 (τ/6Gyr)^0.5 and changes of radial action as sqrt(<)ΔJ_R>²~63kpckms^–1(τ/6Gyr)^0.6 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.