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| Paper: |
Progress and Challenges in SPH Simulations of Disk Galaxy Formation: The Combined Role of Resolution and the Star Formation Density Threshold |
| Volume: |
453, Advances in Computational Astrophysics: Methods, Tools, and Outcome |
| Page: |
289 |
| Authors: |
Mayer, L. |
| Abstract: |
We review progress in cosmological SPH simulations of disk galaxy formation.
We discuss the role of numerical resolution and sub-grid recipes of star formation and feedback from supernovae,
higlighting the important role of a high star formation density threshold comparable to that of star forming
molecular gas phase. Two recent succesfull
examples, in simulations of the formation of gas-rich bulgeless dwarf galaxies and in simulations of late-type
spirals (the ERIS simulations), are presented and discussed. In the ERIS simulations, already
in the progenitors at z = 3 the resolution is above the threshold indicated by previous idealized
numerical experiments as necessary to minimize numerical angular momentum loss (Kaufmann et al. 2007).
A high star formation density
threshold maintains an inhomogeneous interstellar medium, where star formation is clustered, and thus
the local effect of supernovae feedback is enhanced. As a result, outflows are naturally generated removing 2/3 of the
baryons in galaxies with Vvir∼50 km/s and ∼ 30% of the baryons in galaxies with (Vvir ∼
150 km/s).
Low angular momentum baryons are preferentially removed since the strongest bursts of star
formation occur predominantly near the center, especially after a merger event. This produces
pure exponential disks or small bulges depending on galaxy mass, and, correspondingly, slowly
rising or nearly flat rotation curves that match those of observed disk galaxies.
In dwarfs the rapid mass removal by outflows generates a core-like distribution in the
dark matter. Furthermore, contrary to the common picture, in the ERIS spiral galaxies a bar/pseudobulge forms rapidly, and
not secularly, as a result of mergers and interactions at high-z. |
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