Companions to Isolated Elliptical Galaxies : Revisiting the Bothun - Sullivan ( 1977 ) Sample

We investigate the number of physical companion galaxies for a sample of relatively isolated elliptical galaxies. The NASA/IPAC Extragalactic Database (NED) has been used to reinvestigate the incidence of satellite galaxies for a sample of 34 elliptical galaxies, first investigated by Bothun & Sullivan (1977) using a visual inspection of Palomar Sky Survey prints out to a projected search radius of 75 kpc. We have repeated their original investigation using data cataloged data in NED. Nine of these ellipticals appear to be members of galaxy clusters: the remaining sample of 25 galaxies reveals an average of +1.0 ± 0.5 apparent companions per galaxy within a projected search radius of 75 kpc, in excess of two equal-area comparison regions displaced by 150-300 kpc. This is significantly larger than the +0.12 ± 0.42 companions/galaxy found by Bothun & Sullivan for the identical sample. Making use of published radial velocities, mostly available since the completion of the Bothun-Sullivan study, identifies the Co-Director, NASA/IPAC Extraglactic Database (NED), California Institute of Technology, Pasadena, CA 92215