TY - JOUR
T1 - What causes the formation of discs and end of bursty star formation?
AU - Hopkins, Philip F.
AU - Gurvich, Alexander B.
AU - Shen, Xuejian
AU - Hafen, Zachary
AU - Grudić, Michael Y.
AU - Kurinchi-Vendhan, Shalini
AU - Hayward, Christopher C.
AU - Jiang, Fangzhou
AU - Orr, Matthew E.
AU - Wetzel, Andrew
AU - Kereš, Dušan
AU - Stern, Jonathan
AU - Faucher-Giguère, Claude Andre
AU - Bullock, James
AU - Wheeler, Coral
AU - El-Badry, Kareem
AU - Loebman, Sarah R.
AU - Moreno, Jorge
AU - Boylan-Kolchin, Michael
AU - Quataert, Eliot
N1 - Publisher Copyright:
© 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.
PY - 2023/10/1
Y1 - 2023/10/1
N2 - As they grow, galaxies can transition from irregular/spheroidal with 'bursty' star formation histories (SFHs), to discy with smooth SFHs. But even in simulations, the direct physical cause of such transitions remains unclear. We therefore explore this in a large suite of numerical experiments re-running portions of cosmological simulations with widely varied physics, further validated with existing FIRE simulations. We show that gas supply, cooling/thermodynamics, star formation model, Toomre scale, galaxy dynamical times, and feedback properties do not have a direct causal effect on these transitions. Rather, both the formation of discs and cessation of bursty star formation are driven by the gravitational potential, but in different ways. Disc formation is promoted when the mass profile becomes sufficiently centrally concentrated in shape (relative to circularization radii): we show that this provides a well-defined dynamical centre, ceases to support the global 'breathing modes' that can persist indefinitely in less-concentrated profiles and efficiently destroy discs, promotes orbit mixing to form a coherent angular momentum, and stabilizes the disc. Smooth SF is promoted by the potential or escape velocity Vesc (not circular velocity Vc) becoming sufficiently large at the radii of star formation that cool, mass-loaded (momentum-conserving) outflows are trapped/confined near the galaxy, as opposed to escaping after bursts. We discuss the detailed physics, how these conditions arise in cosmological contexts, their relation to other correlated phenomena (e.g. inner halo virialization, vertical disc 'settling'), and observations.
AB - As they grow, galaxies can transition from irregular/spheroidal with 'bursty' star formation histories (SFHs), to discy with smooth SFHs. But even in simulations, the direct physical cause of such transitions remains unclear. We therefore explore this in a large suite of numerical experiments re-running portions of cosmological simulations with widely varied physics, further validated with existing FIRE simulations. We show that gas supply, cooling/thermodynamics, star formation model, Toomre scale, galaxy dynamical times, and feedback properties do not have a direct causal effect on these transitions. Rather, both the formation of discs and cessation of bursty star formation are driven by the gravitational potential, but in different ways. Disc formation is promoted when the mass profile becomes sufficiently centrally concentrated in shape (relative to circularization radii): we show that this provides a well-defined dynamical centre, ceases to support the global 'breathing modes' that can persist indefinitely in less-concentrated profiles and efficiently destroy discs, promotes orbit mixing to form a coherent angular momentum, and stabilizes the disc. Smooth SF is promoted by the potential or escape velocity Vesc (not circular velocity Vc) becoming sufficiently large at the radii of star formation that cool, mass-loaded (momentum-conserving) outflows are trapped/confined near the galaxy, as opposed to escaping after bursts. We discuss the detailed physics, how these conditions arise in cosmological contexts, their relation to other correlated phenomena (e.g. inner halo virialization, vertical disc 'settling'), and observations.
KW - Galaxy: structure
KW - ISM: structure
KW - galaxies: evolution
KW - galaxies: formation
KW - galaxies: general
KW - galaxies: star formation
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U2 - 10.1093/mnras/stad1902
DO - 10.1093/mnras/stad1902
M3 - Article
AN - SCOPUS:85167959568
SN - 0035-8711
VL - 525
SP - 2241
EP - 2286
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 2
ER -