Dark Energy: Measurement by the DEEP2 Redshift Survey

The DEEP2 redshift survey has now covered $\sim$2.5 degrees$^{2}$ of sky and obtained nearly 40,000 spectra; the survey is nearly finished, and I shall describe what has been accomplished with all that Keck time! One of our fields is the Extended Groth Strip (EGS), a region where deep imaging is being obtained with Chandra, Spitzer, GALEX, VLA, and HST/ACS and will be the subject of Sunyaev-Zel'dovich observations. We will eventually provide 17,000 redshifts. In three other regions, we have used three-color imaging to efficiently select galaxies with magnitude R$_{AB}$$<$24.1 and redshifts in the range 0.7 $<$z$<$1.4. The EGS pointing does not have the preselection. We describe here one method by which DEEP2 can set constraints on the equation of state parameter of the Dark Energy, w. By counting the number of virialized groups and clusters we find in redshift space as a function of their redshift and internal velocity dispersion, we probe both the volume element and the growth of structure at z$\sim$1, each of which depends on w. We find 320 groups in the volume, and show how it measures w, but also depends on the bias in the velocity field of galaxies in clusters, b$_{v}$. Studies of this effect are underway.