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| Cuspy halo problem | |
|---|---|
| Name | Cuspy halo problem |
| Field | Astrophysics, Cosmology |
| Introduced | 1990s |
Cuspy halo problem The cuspy halo problem is an astrophysical discrepancy between predictions from cold dark matter simulations and rotation curve measurements of dwarf galaxies and low surface brightness galaxies. Observational surveys and theoretical studies from groups associated with University of California, Berkeley, Max Planck Society, Harvard University, Princeton University, and European Southern Observatory have highlighted tensions that motivate alternative dark matter models and baryonic feedback mechanisms.
Early analytical work and numerical studies connected to James Peebles, Blumenthal et al., Navarro–Frenk–White, A. V. Kravtsov, Simon D. M. White predicted steep central density cusps in virialized halos formed in hierarchical collapse scenarios. Seminal cold dark matter simulations developed by teams at Los Alamos National Laboratory, Lawrence Berkeley National Laboratory, California Institute of Technology, Max Planck Institute for Astrophysics, and Kavli Institute for Cosmology produced universal profiles with inner slopes near -1 to -1.5, conflicting with inferred cores from rotation curve analyses by observers at Carnegie Institution for Science, University of Cambridge, University of Arizona, and University of Groningen.
High-resolution rotation curve observations from instruments at W. M. Keck Observatory, Very Large Telescope, Arecibo Observatory, Green Bank Telescope, and surveys like the Sloan Digital Sky Survey indicate shallower central density distributions in many dwarf and low surface brightness systems. Studies by teams affiliated with Carnegie Institution for Science, Max Planck Institute for Astronomy, Johns Hopkins University, University of California, Santa Cruz, and National Radio Astronomy Observatory use measurements of HI kinematics, Hα spectroscopy, and stellar dynamics to argue for constant-density cores in objects studied by groups led by Stacy S. McGaugh, Marcelo A. de Blok, Robert C. Kennicutt Jr., James S. Bullock, and Andrey V. Kravtsov.
Proposed solutions include baryonic feedback processes studied at NASA, European Space Agency, Institute for Advanced Study, Max Planck Society, and University of Chicago that invoke supernova-driven outflows, stellar winds, and episodic gas inflows examined by researchers such as Andrew Pontzen, Francesco Governato, Joel Primack, Avishai Dekel, and Risa H. Wechsler. Alternative dark matter models explored at CERN, Fermilab, Perimeter Institute, SLAC National Accelerator Laboratory, and Brookhaven National Laboratory include warm dark matter, self-interacting dark matter, fuzzy dark matter, and mixed dark sector proposals developed by teams including Kevork Abazajian, Mark Vogelsberger, David N. Spergel, Paul J. Steinhardt, and Lam Hui.
High-resolution N-body and hydrodynamical simulations from collaborations at Illustris Project, EAGLE collaboration, FIRE project, Millennium simulation, and Via Lactea employ codes like GADGET, AREPO, RAMSES, and ChaNGa developed by groups at Max Planck Institute for Astrophysics, Heidelberg Institute for Theoretical Studies, Lawrence Livermore National Laboratory, University of Zurich, and Princeton University. Convergence studies by Volker Springel, Simon D. M. White, Tom Abel, Naoki Yoshida, and Chris Power examine resolution limits, two-body relaxation, softening length choices, and subgrid feedback prescriptions that affect inferred central density slopes in halos simulated for projects funded by National Science Foundation, European Research Council, DOE, and NASA.
Constraints derived from inner halo structure inform particle physics models investigated at CERN, Fermilab, Institute for High Energy Physics, SLAC National Accelerator Laboratory, and Perimeter Institute. Self-interaction cross section bounds, particle mass limits for warm dark matter, and de Broglie wavelength scales for ultra-light axion-like particles have been proposed by theorists including Savas Dimopoulos, Joseph Silk, Uros Seljak, Katherine Freese, and Seth A. Shapiro. Collider searches, direct detection experiments like LUX, XENON1T, PandaX, and indirect probes from Fermi Gamma-ray Space Telescope and AMS-02 complement astrophysical inferences from halo cores and cusps.
Contemporary debates involve teams at Harvard–Smithsonian Center for Astrophysics, Institute of Astronomy, Cambridge, University of California, Santa Cruz, Columbia University, and University of Toronto weighing baryonic versus particle physics solutions, with methodological critiques from researchers such as Joop Schaye, Mark Fardal, Adrianne Slyz, Ruth Durrer, and Evan Scannapieco. Open questions include the universality of inner density slopes across environments studied by Galaxy And Mass Assembly, the role of environmental processes probed by Hubble Space Telescope, and the interpretation of dwarf satellite data from surveys like DES and Pan-STARRS, motivating further observations by James Webb Space Telescope and simulations at Oak Ridge National Laboratory.