X-ray properties of lyman break galaxies in the great observatories origins deep survey

We constrain the X-ray emission properties of Lyman break galaxies (LBGs) at z approximate to 3 - 6 using the approximate to2 Ms Chandra Deep Field North and approximate to1 Ms Chandra Deep Field South. Large samples of LBGs were discovered using the Hubble Space Telescope as part of the Great Observatories Origins Deep Survey ( GOODS). Deep optical and X-ray imaging over the GOODS fields have allowed us to place the most significant constraints on the X-ray properties of LBGs to date. Mean X-ray properties of 449, 1734, 629, and 247 LBGs with z similar to 3, 4, 5, and 6, respectively, were determined using stacking techniques. When stacked, we detect X-ray emission from LBGs at z similar to 3 (similar to 7 sigma) and from an optically bright subset (brightest 25%) of LBGs at z similar to 4 (similar to 3 sigma); the latter is the highest redshift detection yet for "normal'' galaxies in the X-ray band. The effective exposure times for these stacked observations are approximate to0.7 and 0.5 Gs, respectively. The derived average rest-frame 2.0 - 8.0 keV luminosities are 1.5 x 10(41) and 1.4 x 10(41) ergs s(-1), respectively. X-ray emission from these LBGs is likely due to high-mass X-ray binaries and Type II supernovae; the corresponding star formation rates are approximate to 10 - 30 M-. yr(-1). The X-ray-to B- band mean luminosity ratio (L-X/L-B) at z similar to 3 is somewhat elevated with respect to that measured for starburst galaxies in the local universe (significance similar to 3 sigma). When stacking full samples of LBGs at z similar to 4, 5, and 6, we do not obtain significant detections (< 3 σ) and derive rest-frame 2.0 - 8.0 keV luminosity upper limits (3 σ) of 0.9, 2.8, and 7.1 x 10(41) ergs s(-1), respectively. These upper limits constrain any widespread active galactic nucleus (AGN) activity in these objects to be modest at best. Furthermore, we find that ∼0.5% of our LBGs from z ≈ 3 to z ≈ 6 are detected individually in the X-ray band. These LBGs have spectral shapes and luminosities characteristic of moderate-power AGNs (e.g., Seyfert galaxies and quasars).