Phase-space simulations of prompt cusps: simulating the formation of the first haloes without artificial fragmentation

Lurdes Ondaro-Mallea (Corresponding author), Raul E. Angulo, Jens Stücker, Oliver Hahn, Simon D. M. White

Publications: Contribution to journalArticlePeer Reviewed

Abstract

The first generation of haloes forms from the collapse of the smallest peaks in the initial density field. N-body simulations of this process suggest a prompt formation of a steep power-law cusp, but these calculations are plagued by numerical artefacts that cast some doubt on this result. Here, we develop new simulation methods based on the dark matter phase-space sheet approach and present results that are entirely free of artificial clumps. We find that a cusp with densityr-1.5 is indeed formed promptly, subsequently accreting a more extended halo and participating in the hierarchical growth of later halo generations. However, our simulations also suggest that the presence of artificial clumps just before peak collapse can significantly shallow the inner profiles of the cusps. We use N-body simulations with controlled amounts of small-scale power to place a conservative upper limit on the scales affected by artificial clumps. Finally, we used these results to simulate the collapse of the first generation of peaks of various types and in different cosmologies, finding prompt cusps to form in all cases. We conclude that prompt cusps are a generic feature of the collapse of peaks on the free-streaming scale of the initial density field, and their structure can safely be studied using N-body simulations provided care is taken to excise the region potentially affected by artificial clumps.

Original languageEnglish
Pages (from-to)10802-10821
Number of pages20
JournalMonthly Notices of the Royal Astronomical Society
Volume527
Issue number4
DOIs
Publication statusPublished - 1 Feb 2024

Austrian Fields of Science 2012

  • 103004 Astrophysics
  • 103044 Cosmology

Keywords

  • Astrophysics - Astrophysics of Galaxies
  • Astrophysics - Cosmology and Nongalactic Astrophysics
  • Dark Matter
  • large-scale structure of Universe
  • methods: numerical
  • dark matter

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