Oscar Agertz

In response to recent observations from JWST and Atacama Large Millimeter Array, we explore a new class of dynamically self-consistent models that mimics a plausible progenitor of the Milky Way over a wide range of disk gas fractions, f_gas. The high gas surface densities encourage vigorous star formation, which in turn couples with the gas to drive turbulence. We show that this coupling through momentum recoil drives a random walk of the baryonic potential minimum with respect to total gravitational potential, Φ_tot(R, f, z). The amplitude of the bulk motion depends on the feedback strength, which in turn is directly associated with f_gas. At its most extreme, when gas is the sole contributor to the disk potential (f_gas = 100%), the amplitude of the walk can reach up to R ≈ 5 kpc within Φ_tot. The disk dominates over dark matter (f_disk ≳ 50%) within R_s = 2.2R_disk, where R_disk is the exponential disk scale length. For a lower f_disk and/or f_gas, the 3D sloshing amplitude and velocity are reduced. The combination of strong feedback and sloshing leads to the newly formed stars being dynamically heated and settling to a more spatially extended disk population. The 3D heating process is roughly isotropic but its effects are more noticeable in |z| due to the initial dynamical coldness of the star-forming disk. Such a disk has enhanced [α/Fe] stellar abundances and a vertical (but no radial) gradient in stellar age and metallicity, both consistent with the Milky Way’s thick stellar disk.