TY - JOUR
T1 - The origin of the diverse morphologies and kinematics of MilkyWay-mass galaxies in the FIRE-2 simulations
AU - Garrison-Kimmel, Shea
AU - Hopkins, Philip F.
AU - Wetzel, Andrew
AU - El-Badry, Kareem
AU - Sanderson, Robyn E.
AU - Bullock, James S.
AU - Ma, Xiangcheng
AU - van de Voort, Freeke
AU - Hafen, Zachary
AU - Faucher-Giguère, Claude André
AU - Hayward, Christopher C.
AU - Quataert, Eliot
AU - Kereš, Dušan
AU - Boylan-Kolchin, Michael
N1 - Publisher Copyright:
© 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.
PY - 2018/12/11
Y1 - 2018/12/11
N2 - We use hydrodynamic cosmological zoom-in simulations from the Feedback in Realistic Environments project to explore the morphologies and kinematics of 15 Milky Way (MW)- mass galaxies. Our sample ranges from compact, bulge-dominated systems with 90 per cent of their stellar mass within 2.5 kpc to well-ordered discs that reach ≳15 kpc. The gas in our galaxies always forms a thin, rotation-supported disc at z = 0, with sizes primarily determined by the gas mass. For stars, we quantify kinematics and morphology both via the fraction of stars on disc-like orbits and with the radial extent of the stellar disc. In this mass range, stellar morphology and kinematics are poorly correlated with the properties of the halo available from dark matter-only simulations (halo merger history, spin, or formation time). They more strongly correlate with the gaseous histories of the galaxies: those that maintain a high gas mass in the disc after z ~ 1 develop well-ordered stellar discs. The best predictor of morphology we identify is the spin of the gas in the halo at the time the galaxy formed 1/2 of its stars (i.e. the gas that builds the galaxy). High-z mergers, before a hot halo emerges, produce some of the most massive bulges in the sample (from compact discs in gas-rich mergers), while later-forming bulges typically originate from internal processes, as satellites are stripped of gas before the galaxies merge. Moreover, most stars in z = 0 MW-mass galaxies (even z = 0 bulge stars) form in a disc: ≳60-90 per cent of stars begin their lives rotationally supported.
AB - We use hydrodynamic cosmological zoom-in simulations from the Feedback in Realistic Environments project to explore the morphologies and kinematics of 15 Milky Way (MW)- mass galaxies. Our sample ranges from compact, bulge-dominated systems with 90 per cent of their stellar mass within 2.5 kpc to well-ordered discs that reach ≳15 kpc. The gas in our galaxies always forms a thin, rotation-supported disc at z = 0, with sizes primarily determined by the gas mass. For stars, we quantify kinematics and morphology both via the fraction of stars on disc-like orbits and with the radial extent of the stellar disc. In this mass range, stellar morphology and kinematics are poorly correlated with the properties of the halo available from dark matter-only simulations (halo merger history, spin, or formation time). They more strongly correlate with the gaseous histories of the galaxies: those that maintain a high gas mass in the disc after z ~ 1 develop well-ordered stellar discs. The best predictor of morphology we identify is the spin of the gas in the halo at the time the galaxy formed 1/2 of its stars (i.e. the gas that builds the galaxy). High-z mergers, before a hot halo emerges, produce some of the most massive bulges in the sample (from compact discs in gas-rich mergers), while later-forming bulges typically originate from internal processes, as satellites are stripped of gas before the galaxies merge. Moreover, most stars in z = 0 MW-mass galaxies (even z = 0 bulge stars) form in a disc: ≳60-90 per cent of stars begin their lives rotationally supported.
KW - Cosmology: theory
KW - Galaxies: bulges
KW - Galaxies: evolution
KW - Galaxies: formation
KW - Galaxies: spiral
KW - Galaxies: structure
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U2 - 10.1093/mnras/sty2513
DO - 10.1093/mnras/sty2513
M3 - Article
C2 - 30598560
AN - SCOPUS:85054267738
SN - 0035-8711
VL - 481
SP - 4133
EP - 4157
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 3
ER -