A Study of the Projected Galaxy Density around Nine Isolated Elliptical Galaxies

Abstract

Using V-band imagery, we present results from a comparative density analysis of the local environments surrounding nine elliptical galaxies, with the objective of validating that these objects reside in extremely isolated environments. We have developed a technique that compares galaxy number density enhancements within well-studied clusters and loose groups with apparent clusterings of faint, predominantly uncataloged galaxies that are present in the fields of the isolated elliptical galaxy (IEG) candidates. The unique feature of this technique is the ability to combine size information of density peaks with number density values in order to place upper or lower limits on the distances of an apparent clustered structure in an IEG field. The utility of this technique is that probable physical association between an IEG and a clustered structure can be refuted without need of redshift information for the faint field sources. Of the nine IEG candidates studied, we conclude that one of the galaxies has possible membership with a loose group of Local Group density. Four other IEG candidates have environments that show density enhancements in the field that are possible loose groups with densities similar to the Leo or Dorado groups, but physical association with the IEGs is unlikely. The remaining four galaxies have environments that are confirmed to be isolated down to the detection limits that are detailed in the paper.