TY - JOUR
T1 - Keeping It Cool
T2 - Much Orbit Migration, yet Little Heating, in the Galactic Disk
AU - Frankel, Neige
AU - Sanders, Jason
AU - Ting, Yuan Sen
AU - Rix, Hans Walter
N1 - Publisher Copyright:
© 2020. The American Astronomical Society. All rights reserved..
PY - 2020/6/10
Y1 - 2020/6/10
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85087355175&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/ab910c
DO - 10.3847/1538-4357/ab910c
M3 - Article
SN - 0004-637X
VL - 896
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 15
ER -