Core formation in high-z massive haloes: Heating by post-compaction satellites and response to AGN outflows

Avishai Dekel*, Jonathan Freundlich, Fangzhou Jiang, Sharon Lapiner, Andreas Burkert, Daniel Ceverino, Xiaolong Du, Reinhard Genzel, Joel Primack

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Observed rotation curves in star-forming galaxies indicate a puzzling dearth of dark matter in extended flat cores within haloes of mass ≥1012M⊙ at z ∼2. This is not reproduced by current cosmological simulations, and supernova-driven outflows are not effective in such massive haloes. We address a hybrid scenario where post-compaction merging satellites heat up the dark-matter cusps by dynamical friction, allowing active galactic nucleus (AGN)-driven outflows to generate cores. Using analytic and semi-analytic models (SatGen), we estimate the dynamical friction heating as a function of satellite compactness for a cosmological sequence of mergers. Cosmological simulations (VELA) demonstrate that satellites of initial virial masses >1011.3M⊙, which undergo wet compactions, become sufficiently compact for significant heating. Constituting a major fraction of the accretion on to haloes ≥1012M⊙, these satellites heat up the cusps in half a virial time at z ∼2. Using a model for outflow-driven core formation (CuspCore), we demonstrate that the heated dark-matter cusps develop extended cores in response to removal of half the gas mass, while the more compact stellar systems remain intact. The mergers keep the dark matter hot, while the gas supply, fresh and recycled, is sufficient for the AGN outflows. AGNs indeed become effective in haloes ≥1012M⊙, where the black hole growth is no longer suppressed by supernovae and its compaction-driven rapid growth is maintained by a hot circumgalactic medium. For simulations to reproduce the dynamical friction effects, they should resolve the compaction of the massive satellites and avoid artificial tidal disruption. AGN feedback could be boosted by clumpy black hole accretion and clumpy response to AGN.

Original languageEnglish
Pages (from-to)999-1019
Number of pages21
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - 1 Nov 2021
Externally publishedYes


  • black holes
  • dark matter
  • galaxies: discs
  • galaxies: formation
  • galaxies: haloes
  • galaxies: mergers


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