Cusps and rotation curves in cold-dark-matter haloes

Area of Science:

• Cosmology
• Astrophysics
• Computational Physics

Background:

• Cold-dark-matter (CDM) is a leading paradigm for structure formation.
• Understanding the inner structure of CDM halos is crucial for testing this paradigm.
• Previous studies suggested mass-independent profiles and central cusps in CDM halos.

Purpose of the Study:

• To investigate the inner structure of CDM halos using recent numerical simulations.
• To confirm and extend previous findings on halo mass profiles and density distributions.
• To analyze the implications of simulation results for reconciling CDM theory with observations of low-surface-brightness (LSB) galaxies.

Main Methods:

• Performed high-resolution numerical simulations of CDM halo formation.
• Analyzed the resulting dark matter density profiles and mass distributions.
• Compared simulated circular-velocity curves with observational data from LSB galaxies.

Main Results:

• Confirmed that CDM halo mass profiles are largely independent of halo mass.
• Found evidence for central density cusps, with slopes constrained by simulation resolution.
• Simulated circular-velocity curves generally agree with LSB galaxy rotation curves, but discrepancies exist.
• Ruled out very steep cusps (beta(0) approximately -1.5) in highest resolution simulations; slopes beta(0) less, similar -1 are consistent.

Conclusions:

• The inner structure of CDM halos is characterized by mass-independent profiles and central cusps.
• The precise slope of these cusps is constrained by numerical resolution.
• Discrepancies with LSB galaxy rotation curves may be explained by the complex 3D structure of triaxial halos, rather than a failure of the CDM model.
• The CDM paradigm remains viable without drastic revision.