ΛCDM and the distribution of dark matter in galaxies: A constant–density halo around DDO 47

¹ International School for Advanced Studies SISSA/ISAS, Trieste, Italy e-mail: borri@sissa.it
² California Institute of Technology, Pasadena, CA 91125, USA e-mail: fw@astro.caltech.edu

Corresponding author: P. Salucci, salucci@sissa.it

Received: 3 September 2002
Accepted: 10 April 2003

Abstract

In this paper we present a test case for the existence of a core in the density distribution of dark halos around galaxies. DDO 47 has a rotation curve that increases linearly from the first data point, at 300 pc, up to the last one, at 5 kpc. This profile implies the presence of a (dark) halo with an (approximately) constant density over the region mapped by data. This evidences the inability of standard Λ Cold Dark Matter scenario to account for the dark matter distribution around galaxies, and points toward the existence of an intriguing halo scale–length of homogeneity. This work adds up to the results of Blais-Ouellette et al. ([CITE]), Trott & Webster ([CITE]), Binney & Evans (2002), de Blok & Bosma ([CITE]) and Bottema ([CITE]) in suggesting that at galactic scales CDM theory should incorporate, as an intrinsic property, a “density core" feature.