TY - JOUR
T1 - Rapid filamentary accretion as the origin of extended thin discs
AU - Kretschmer, Michael
AU - Agertz, Oscar
AU - Teyssier, Romain
N1 - Funding Information:
The authors thank the referee for their constructive comments that improved the quality of the paper. We acknowledge stimulating discussions with Lorenzo Posti, Pedro Capelo, Lucio Mayer, and Robert Feldmann. This work was supported by the Swiss National Supercomputing Center (CSCS) project s890 - 'Predictive models for galaxy formation' and the Swiss National Science Foundation (SNSF) project 172535 - 'Multi-scale multi-physics models of galaxy formation'. The simulations in this work were performed on Piz Daint at the Swiss Supercomputing Center (CSCS) in Lugano, and the analysis was performed with equipment maintained by the Service and Support for Science IT, University of Zurich. We made use of the PYNBODY package (Pontzen et al. 2013). OA acknowledges support from the Knut and Alice Wallenberg Foundation and the Swedish Research Council (grant 2014-5791).
Funding Information:
The authors thank the referee for their constructive comments that improved the quality of the paper. We acknowledge stimulating discussions with Lorenzo Posti, Pedro Capelo, Lucio Mayer, and Robert Feldmann. This work was supported by the Swiss National Supercomputing Center (CSCS) project s890 – ‘Predictive models for galaxy formation’ and the Swiss National Science Foundation (SNSF) project 172535 – ‘Multi-scale multi-physics models of galaxy formation’. The simulations in this work were performed on Piz Daint at the Swiss Supercomputing Center (CSCS) in Lugano, and the analysis was performed with equipment maintained by the Service and Support for Science IT, University of Zurich. We made use of the PYNBODY package (Pontzen et al. 2013). OA acknowledges support from the Knut and Alice Wallenberg Foundation and the Swedish Research Council (grant 2014-5791).
Publisher Copyright:
© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
PY - 2020
Y1 - 2020
N2 - Galactic outflows driven by stellar feedback are crucial for explaining the inefficiency of star formation in galaxies. Although strong feedback can promote the formation of galactic discs by limiting star formation at early times and removing low angular momentum (AM) gas, it is not understood how the same feedback can result in diverse objects such as elliptical galaxies or razor thin spiral galaxies. We investigate this problem using cosmological zoom-in simulations of two galaxies forming within 1012 M☉ haloes with almost identical mass accretion histories and halo spin parameters. However, the two resulting galaxies end up with very different bulge-to-disc ratios at z = 0. At z > 1.5, the two galaxies feature a surface density of star formation ΣSFR ≃ 10 M☉ yr−1 kpc−2, leading to strong outflows. After the last starburst episode, both galaxies feature a dramatic gaseous disc growth from 1 to 5 kpc during 1 Gyr, a decisive event we dub 'the Grand Twirl'. After this event, the evolutionary tracks diverge strongly, with one galaxy ending up as a bulge-dominated galaxy, whereas the other ends up as a disc-dominated galaxy. The origins of this dichotomy are the AM of the accreted gas, and whether it adds constructively to the initial disc angular momentum. The build-up of this extended disc leads to a rapid lowering of ΣSFR by over two orders of magnitude with ΣSFR ≲ 0.1 M☉ yr−1 kpc−2, in remarkable agreement with what is derived from Milky Way stellar populations. As a consequence, supernovae explosions are spread out and cannot launch galactic outflows anymore, allowing for the persistence of a thin, gently star-forming, extended disc.
AB - Galactic outflows driven by stellar feedback are crucial for explaining the inefficiency of star formation in galaxies. Although strong feedback can promote the formation of galactic discs by limiting star formation at early times and removing low angular momentum (AM) gas, it is not understood how the same feedback can result in diverse objects such as elliptical galaxies or razor thin spiral galaxies. We investigate this problem using cosmological zoom-in simulations of two galaxies forming within 1012 M☉ haloes with almost identical mass accretion histories and halo spin parameters. However, the two resulting galaxies end up with very different bulge-to-disc ratios at z = 0. At z > 1.5, the two galaxies feature a surface density of star formation ΣSFR ≃ 10 M☉ yr−1 kpc−2, leading to strong outflows. After the last starburst episode, both galaxies feature a dramatic gaseous disc growth from 1 to 5 kpc during 1 Gyr, a decisive event we dub 'the Grand Twirl'. After this event, the evolutionary tracks diverge strongly, with one galaxy ending up as a bulge-dominated galaxy, whereas the other ends up as a disc-dominated galaxy. The origins of this dichotomy are the AM of the accreted gas, and whether it adds constructively to the initial disc angular momentum. The build-up of this extended disc leads to a rapid lowering of ΣSFR by over two orders of magnitude with ΣSFR ≲ 0.1 M☉ yr−1 kpc−2, in remarkable agreement with what is derived from Milky Way stellar populations. As a consequence, supernovae explosions are spread out and cannot launch galactic outflows anymore, allowing for the persistence of a thin, gently star-forming, extended disc.
KW - Galaxies: evolution
KW - Galaxies: formation
KW - Galaxies: star formation
KW - Methods: numerical
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U2 - 10.1093/mnras/staa2243
DO - 10.1093/mnras/staa2243
M3 - Article
AN - SCOPUS:85092487541
SN - 0035-8711
VL - 497
SP - 4346
EP - 4356
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 4
ER -