2001/10/31 by Shmuel Balberg, Stuart L. Shapiro, Shogo Inagaki · 8 citations
Physics and Astronomy · #Astronomy #Astrophysics #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #Dark matter #Dark matter halo #Galaxies: Formation, Evolution, Phenomena #Galaxy #Gravitational collapse #Halo #Physics #Power law #Velocity dispersion #astro-ph #gr-qc
paper · pdf · doi:10.1086/339038
published as Astrophys.J. 568 (2002) 475-487 · ApJ in press (to appear in April), 12 pages. Extremely minor changes to agree with published version
arxiv created 2002/03/11 · openalex publication_date 2002/04/01 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We study the evolution of an isolated spherical halo of self-interacting dark matter (SIDM) in the gravothermal fluid formalism. We show that the thermal relaxation time t r of an SIDM halo with the central density and velocity dispersion of a typical dwarf galaxy is significantly shorter than its age. We find a self-similar solution for the evolution of an SIDM halo in the limit where the mean free path between collisions, λ, is longer than the gravitational scale height H everywhere. Typical halos formed in this long mean free path regime relax to a quasi-stationary gravothermal density profile characterized by a nearly homogeneous core and a power-law halo where ρ ∝ r -2.19 . We solve the more general time-dependent problem and show that the contracting core evolves to sufficiently high density that λ inevitably becomes smaller than H in the innermost region. The core undergoes secular collapse to a singular state (the "gravothermal catastrophe") in a time t coll ≈ 290 t r , which is longer than the Hubble time for a typical dark matter-dominated galaxy core at the present epoch. Our model calculations are consistent with previous more detailed N -body simulations for SIDM, providing a simple physical interpretation of their results and extending them to higher spatial resolution and longer evolution times. At late times, mass loss from the contracting dense inner core to the ambient halo is significantly moderated, so that the final mass of the inner core may be appreciable when it becomes relativistic and radially unstable to dynamical collapse to a black hole.