Core Formation in High-z Massive Haloes: Heating by Post Compaction Satellites and Response to AGN Outflows

Abstract

Observed rotation curves in star-forming galaxies indicate a puzzling dearth of dark matter in extended flat cores within haloes of mass $\ge 10^{12}{M}_{\odot }$ at $z\sim 2$. 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 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 $>10^{11.3}{M}_{\odot }$, that undergo wet compactions, become sufficiently compact for significant heating. Constituting a major fraction of the accretion onto haloes $\ge 10^{12}{M}_{\odot }$, these satellites heat-up the cusps in half a virial time at $z\sim 2$. 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. AGN indeed become effective in haloes $\ge 10^{12}{M}_{\odot }$, where the black-hole growth is no longer suppressed by supernovae and its compaction-driven rapid growth is maintained by a hot CGM. 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.

25+10 pages, 10+8 figures

References in corpus (16)

• High-Resolution Rotation Curves and Galaxy Mass Models from THINGS
• Compaction and Quenching of High-z Galaxies in Cosmological Simulations: Blue and Red Nuggets
• High-resolution mass models of dwarf galaxies from LITTLE THINGS
• Generating Dark Matter Halo Merger Trees
• The dark nemesis of galaxy formation: why hot haloes trigger black hole growth and bring star formation to an end
• Strongly baryon-dominated disk galaxies at the peak of galaxy formation ten billion years ago
• Dark Matter Substructure in Numerical Simulations: A Tale of Discreteness Noise, Runaway Instabilities, and Artificial Disruption
• Black Holes on FIRE: Stellar Feedback Limits Early Feeding of Galactic Nuclei
• On the Lack of Evolution in Galaxy Star Formation Efficiency
• Merger Rates of Dark-Matter Haloes
• CANDELS: Elevated Black Hole Growth in the Progenitors of Compact Quiescent Galaxies at z~2
• DASH: a library of dynamical subhalo evolution
• The combined effect of AGN and supernovae feedback in launching massive molecular outflows in high-redshift galaxies
• NIHAO-XXIII: Dark Matter density shaped by Black Hole feedback
• The Mass Function of Unprocessed Dark Matter Halos and Merger Tree Branching Rates
• Dark Matter Fraction in z~1 Star-Forming Galaxies