paper

The bursty origin of the Milky Way thick disc

arXiv:2103.03888 · doi:10.1093/mnras/stab1339

Abstract

We investigate thin and thick stellar disc formation in Milky-Way-mass galaxies using twelve FIRE-2 cosmological zoom-in simulations. All simulated galaxies experience an early period of bursty star formation that transitions to a late-time steady phase of near-constant star formation. Stars formed during the late-time steady phase have more circular orbits and thin-disc-like morphology at , whilst stars born during the bursty phase have more radial orbits and thick-disc structure. The median age of thick-disc stars at correlates strongly with this transition time. We also find that galaxies with an earlier transition from bursty to steady star formation have a higher thin-disc fractions at . Three of our systems have minor mergers with LMC-size satellites during the thin-disc phase. These mergers trigger short starbursts but do not destroy the thin disc nor alter broad trends between the star formation transition time and thin/thick disc properties. If our simulations are representative of the Universe, then stellar archaeological studies of the Milky Way (or M31) provide a window into past star-formation modes in the Galaxy. Current age estimates of the Galactic thick disc would suggest that the Milky Way transitioned from bursty to steady phase 6.5 Gyr ago; prior to that time the Milky Way likely lacked a recognisable thin disc.

arXiv comment15 pages, 11 figures, submitted to MNRAS

References in corpus (79)

Cited by in corpus (41)