2008/11/07 by Yoshiaki Sofue · 3 citations
Physics and Astronomy · #Astronomy #Astrophysics #Cosmology and Gravitation Theories #Dark matter halo #Dwarf galaxy #Galactic halo #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy formation and evolution #Galaxy group #Galaxy rotation curve #Geometry #Group (periodic table) #Halo #Local Group #Physics #Rotation (mathematics) #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1093/pasj/61.2.153
PASJ in press, 10 pages
arxiv created 2008/11/07 · openalex publication_date 2009/04/25 · arxiv updated 2015/05/12 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We construct a Galacto-Local Group rotation curve, combining the Galactic rotation curve with a diagram, where the galacto-centric radial velocities of the outer globular clusters and the member galaxies of the Local Group are plotted against their galacto-centric distances. The high-velocity ends of this pseudo rotation curve within a radius of R∼ 150 kpc are well traced by a rotation curve calculated for the NFW (Navaro, Frenk, White) and Burkert dark halo models. The NFW model indicates that the Galaxy’s mass within 385 kpc, half the distance to M 31, is ∼4×1011M_\odot. High-velocity ends of the pseudo rotation curve for the entire Local Group up to 1.5 Mpc indicate an isothermal nature with a terminal velocity of ∼200 kms-1. In order for the Local Group to be gravitationally bound, an order-of-magnitude larger mass than those of the Galaxy and M 31 is required. This fact suggests that the Local Group contains dark matter of mass ∼5×1012M_\odot, filling the space between the Galaxy and M 31. The mass density of the Galactic dark halo becomes equal to that of the Local Group’s dark matter at R∼ 100 kpc, beyond which the intracluster dark matter dominates. If we define the Galaxy’s radius at this distance, the enclosed Galactic mass is ∼3×1011M_\odot.