The X-Ray Spectral Properties of SCUBA Galaxies

摘要: Deep SCUBA surveys have uncovered a large population of massive submillimeter-emitting galaxies (SMGs; f850μm 4 mJy) at z 1. Although it is generally believed that these host intense star formation activity, there growing evidence substantial fraction also harbor an active galactic nucleus (AGN; i.e., accreting super-massive black hole [SMBH]). We present here possibly the strongest for this viewpoint to date: combination ultradeep X-ray observations (the 2 Ms Chandra Field-North) and deep Keck spectroscopic data SMGs with radio counterparts. find majority (≈75%) radio-selected spectroscopically identified AGN activity; other ≈25% properties consistent (X-ray-derived rates ≈1300-2700 M☉ yr-1). The AGNs those nearby luminous (Γ ≈ 1.8 ± 0.5, NH 1020-1024 cm-2, LX 1043-1044.5 ergs s-1), (≈80%) are heavily obscured (NH 1023 cm-2). construct composite rest-frame 2-20 keV spectra three different obscuration classes [NH 5 × cm-2], which reveal features not seen in individual spectra. An ≈1 equivalent width Fe Kα emission line spectrum most AGNs, suggesting Compton-thick or near absorption. Even taking into account effects absorption, we average far-IR luminosity ratio AGN-classified (LX/LFIR = 0.004) approximately 1 order magnitude below found typical quasars. This result suggests activity (of ≈1000 yr-1) dominates bolometric output SMGs. However, explore possibility components intrinsically less than quasars postulate some may be dominated. investigate implications our results growth holes, discuss prospects deeper observations, scientific potential offered by next generation observatories.