Astronomy and Astrophysics – Astrophysics
Scientific paper
2005-06-27
Astrophys.J.632:736-750,2005
Astronomy and Astrophysics
Astrophysics
16 pages, 9 figures, ApJ in press
Scientific paper
10.1086/444342
Deep SCUBA surveys have uncovered a large population of massive submm galaxies (SMGs) at z>~1. Although it is generally believed that these galaxies host intense star-formation activity, there is growing evidence that a substantial fraction also harbor an AGN. We present here possibly the strongest evidence for this viewpoint to date: the combination of ultra-deep X-ray observations (the 2 Ms CDF-N) and deep Keck spectroscopic data. We find that the majority (~75%) of the spectroscopically identified SMGs host AGN activity; the other ~25% have X-ray properties consistent with star formation (X-ray derived SFRs of ~1300-2700 solars/yr). The AGNs have properties generally consistent with those of nearby luminous AGNs (L_X~1E43-3E44) and the majority (~80%) are heavily obscured. We construct composite rest-frame 2-20 keV spectra for three different obscuration classes. An ~1 keV equivalent width FeK-alpha emission line is seen in the composite X-ray spectrum of the most heavily obscured AGNs (N_H>5x10^{23}), suggesting Compton-thick or near Compton-thick absorption. Even taking into account the effects of absorption, we find that the average X-ray-FIR ratio of the AGN-classified SMGs is approximately one order of magnitude below that found for typical quasars. This result suggests that intense star-formation activity dominates the bolometric output; however, we also explore whether the X-ray-FIR ratio is intrinsically less than that found for typical quasars and postulate that some SMGs may be AGN dominated. We investigate the growth of massive black holes, discuss prospects for deeper observations, and explore the potential of the next generation of X-ray observatories. (ABRIDGED).
Alexander Dave M.
Bauer Franz Erik
Blain Andrew W.
Brandt Wiliam N.
Chapman Sandra C.
No associations
LandOfFree
The X-ray Spectral Properties of SCUBA Galaxies does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The X-ray Spectral Properties of SCUBA Galaxies, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The X-ray Spectral Properties of SCUBA Galaxies will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-646860