Anisotropic Distribution of Sdss Satellite Galaxies: Planar (not Polar) Alignment

The distribution of satellite galaxies about isolated host galaxies in the second data release of the Sloan Digital Sky Survey (SDSS) is investigated. Host–satellite systems are selected using three different methods, yielding samples of ∼ 2100 satellites, ∼ 1300 satellites, and ∼ 650 satellites. All three samples of satellites show highly significant deviations from isotropy relative to the major axes of the hosts (> 99.99%, > 99.99%, and 99.89% confidence levels, respectively), and the degree of anisotropy is a strong function of the projected radius, rp, at which the satellites are located. In particular, for rp ∼< 100 kpc, satellites are aligned preferentially with the host major axis. This result is in stark contrast to the Holmberg effect, in which satellites are observed to cluster along the minor axis of the host galaxy. The degree of anisotropy in the distribution of the SDSS satellites decreases with projected radius and is consistent with an isotropic distribution at the 1-σ level for 400 kpc ∼< rp ∼< 500 kpc. Subject headings: galaxies: fundamental parameters — galaxies: dwarf — galaxies: halos — galaxies: structure — dark matter