  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
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 survey using combined Chandra
and XMM data. A state of the art extended source finding algorithm has been
applied, and the resultant source catalog, including redshifts from a
spectroscopic follow-up program, is presented. The total number of
spectroscopically identified groups is 25 spanning a redshift range 0.04-0.79.
Approximately 50% of CNOC2 spectroscopically selected groups in the deeper
X-ray (RA14h) field are likely X-ray detections, compared to 20% in the
shallower (RA21h) field. Statistical modeling shows that this is consistent
with expectations, assuming an expected evolution of the Lx-M relation. A
significant detection of a stacked shear signal for both spectroscopic and
X-ray groups indicates that both samples contain real groups of about the
expected mass. We conclude that the current area and depth of X-ray and
spectroscopic facilities provide a unique window of opportunity at z~0.4 to
test the X-ray appearance of galaxy groups selected in various ways. There is
at present no evidence that the correlation between X-ray luminosity and
velocity dispersion evolves significantly with redshift, which implies that
catalogs based on either method can be fairly compared and modeled.

Cosmology and Nongalactic Astrophysics