EXTREMELY ISOLATED EARLY-TYPE GALAXIES IN THE SLOAN DIGITAL SKY SURVEY. I. THE SAMPLE

Abstract

We describe the properties of a sample of extremely isolated early-type galaxies (IEGs) selected from the spectroscopic Sloan Digital Sky Survey. Sample galaxies are isolated from nearest neighbors more luminous than MV = −16.5 by a minimum distance corresponding to 2.5 Mpc and 350 km s−1 in redshift space. The candidate IEGs exhibit a number of unusual features as compared to bulge-dominated galaxies in cluster and group environments, including fainter luminosities, blue colors suggesting possible recent star formation, and smaller physical sizes. The paper is the first in a series analyzing this isolated galaxy sample.