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We present the results of a program to acquire high-quality optical spectraof X-ray sources detected in the E-CDF-S and its central area. Newspectroscopic redshifts are measured for 283 counterparts to Chandra sourceswith deep exposures (t~2-9 hr per pointing) using multi-slit facilities on boththe VLT and Keck thus bringing the total number of spectroscopically-identifiedX-ray sources to over 500 in this survey field. We provide a comprehensivecatalog of X-ray sources detected in the E-CDF-S including the optical andnear-infrared counterparts, and redshifts (both spectroscopic and photometric)that incorporate published spectroscopic catalogs thus resulting in a finalsample with a high fraction (80%) of X-ray sources having secureidentifications. We demonstrate the remarkable coverage of the Lx-z plane nowaccessible from our data while emphasizing the detection of AGNs thatcontribute to the faint end of the luminosity function at 1.5<z<3. Our redshiftcatalog includes 17 type 2 QSOs that significantly increases such samples (2x).With our deepest VIMOS observation, we identify "elusive" optically-faintgalaxies (R~25) at z~2-3 based upon the detection of interstellar absorptionlines; we highlight one such case, an absorption-line galaxy at z=3.208 havingno obvious signs of an AGN in its optical spectrum. In addition, we determinedistances to eight galaxy groups with extended X-ray emission. Finally, wemeasure the physical extent of known large-scale structures (z~0.7) evident inthe CDF-S. While a thick sheet (radial size of 67.7 Mpc) at z~0.67 extends overthe full field, the z~0.73 structure is thin (18.8 Mpc) and filamentary astraced by both AGNs and galaxy groups. In the appendix, we providespectroscopic redshifts for 49 counterparts to fainter X-ray sources detectedonly in the 1 and 2 Ms catalogs, and 48 VLA radio sources not detected inX-rays.

The Extended Chandra Deep Field-South Survey: Optical spectroscopy of faint X-ray sources with the VLT and Keck