The Chandra Deep Field North Survey. XIV. X-Ray–Detected Obscured AGN[CLC]s[/CLC] and Starburst Galaxies in the Bright Submillimeter Source Population

We provide X-ray constraints and perform the first X-ray spectral analysesfor bright (f_850>=5mJy; S/N>=4) SCUBA sources in an 8.4'x8.4' area of the 2 MsChandra Deep Field-North survey containing the Hubble Deep Field-North. X-rayemission is detected from 7 of the 10 bright submm sources in this region,corresponding to an X-ray detected submm source density of ~360 deg^-2 (>~36%of the bright submm source population). Two of the X-ray detected sources havenearby (within 3") X-ray companions, suggesting merging/interacting sources orgravitational lensing effects, and 3 lie within the approximate extent of aproto-cluster candidate. Five of the X-ray detected sources have flat X-rayspectral slopes, suggesting obscured AGN activity. X-ray spectral analysessuggest that one of these AGNs may be a Compton-thick source; of the other 4AGNs, 3 appear to be Compton-thin sources and one has poor constraints. Therest-frame unabsorbed X-ray luminosities of these AGNs are more consistent withthose of Seyfert galaxies than QSOs. Thus, the low X-ray detection rate ofbright submm sources by moderately deep X-ray surveys appears to be due to therelatively low luminosities of the AGNs rather than Compton-thick absorption. Acomparison of these sources to the well-studied heavily obscured AGN NGC6240shows that the average AGN contribution is negligible at submm wavelengths. TheX-ray properties of the other 2 X-ray detected sources are consistent withthose expected from luminous star formation; however, we cannot rule out thepossibility that low-luminosity AGNs are present. The 3 X-ray undetectedsources appear to lie at high redshift (z>4) and could be either AGNs orstarbust galaxies.Comment: AJ in press (February 2003), 16 pages, includes emulateapj5.st