The Coma Cluster of Galaxies: Spectral Classification and Star Formation with the Sloan Digital Sky Survey Spectroscopic Commissioning Data

Abstract

We present the first hour of extra-galactic spectroscopy taken during the early commissioning stages of the Sloan Digital Sky Survey (SDSS) spectroscopic system in June 1999: an observation of the Coma cluster of galaxies. Our data samples the Southern part of this cluster, out to the virial radius. We outline here the main characteristics of the SDSS spectroscopic systems and provide spectral classifications for 196 Coma galaxies. We have investigated three different spectral classification algorithms: measurements of the spectral line strengths, a principal component decomposition and a wavelet analysis. We find that these classification schemes are in broad agreement and can provide physical insight into the evolutionary histories of our cluster galaxies. We find that a significant fraction (25%) of our observed Coma galaxies show signs of recent star-formation activity.