Bounds on the mass and abundance of dark compact objects and black holes in dwarf spheroidal galaxy halos

Abstract

We establish new dynamical constraints on the mass and abundance of compact objects in the halo of dwarf spheroidal galaxies. In order to preserve kinematically cold the second peak of the Ursa Minor dwarf spheroidal (UMi dSph) against gravitational scattering, we place upper limits on the density of compact objects as a function of their assumed mass. The mass of the dark matter constituents cannot be larger than 1000 solar masses at a halo density in UMi's core of 0.35 solar masses/pc^3. This constraint rules out a scenario in which dark halo cores are formed by two-body relaxation processes. Our bounds on the fraction of dark matter in compact objects with masses >3000 solar masses improve those based on dynamical arguments in the Galactic halo. In particular, objects with masses $\sim 10^5$ solar masses can comprise no more than a halo mass fraction $\sim 0.01$. Better determinations of the velocity dispersion of old overdense regions in dSphs may result in more stringent constraints on the mass of halo objects. For illustration, if the preliminary value of 0.5 km/s for the secondary peak of UMi is confirmed, compact objects with masses above $\sim 100$ solar masses could be excluded from comprising all its dark matter halo.

arXiv comment6 pages, 2 figures, accepted for publication in ApJ Letters

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Cited by in corpus (6)

• On the mass of ultra-light bosonic dark matter from galactic dynamics
• An upper limit on the mass of the black hole in Ursa Minor dwarf galaxy
• Tidal radii and escape speeds in dwarf spheroidal galaxies under MOND and dark halos compared
• Sextans' cold substructures as a dynamical judge: Core, Cusp or MOND?
• Dark Matter Subhalos in the Ursa Minor Dwarf Galaxy
• Size Evolution of Early-Type Galaxies and Massive Compact Objects as the Dark Matter