THE ROADMAP FOR UNIFICATION IN GALAXY GROUP SELECTION. I. A SEARCH FOR EXTENDED X-RAY EMISSION IN THE CNOC2 SURVEY**Based on observations with the ESA/NASA XMM-Newton science mission; the European Southern Observatory, Chile; NASA/ESA Chandra X-ray Observatory.

X-ray properties of galaxy groups can unlock some of the most challenging research topics in modern extragalactic astronomy: the growth of structure and its influence on galaxy formation. Only with the advent of the Chandra and XMM-Newton facilities have X-ray observations reached the depths required to address these questions in a satisfactory manner. Here we present an X-ray imaging study of two patches from the CNOC2 spectroscopic galaxy …