Submm-bright X-ray absorbed QSOs at z~2 : insights into the co-evolution of AGN and star-formation

Abstract

We have assembled a sample of 5 X-ray-absorbed and submm-luminous type 1 QSOs at $z \sim 2$ which are simultaneously growing their central black holes through accretion and forming stars copiously. We present here the analysis of their rest-frame UV to submm Spectral Energy Distributions (SEDs), including new Herschel data. Both AGN (direct and reprocessed) and Star Formation (SF) emission are needed to model their SEDs. From the SEDs and their UV-optical spectra we have estimated the masses of their black holes $M_{BH}\sim 10^{9}-10^{10}\,M_{\odot}$, their intrinsic AGN bolometric luminosities $L_{BOL}\sim(0.8 - 20)\times 10^{13} L_{\odot}$, Eddington ratios $L_{BOL}/L_{Edd}\sim 0.1 - 1.1$ and bolometric corrections $L_{BOL}/L_{X,2-10}\sim 30 - 500$. These values are common among optically and X-ray-selected type 1 QSOs (except for RX~J1249), except for the bolometric corrections, which are higher. These objects show very high far-infrared luminosities $L_{FIR}\sim$ (2 - 8)$\times10^{12}\,M_{\odot}$ and Star Formation Rates SFR$\sim 1000 M_{\odot}/$y. From their $L_{FIR}$ and the shape of their FIR-submm emission we have estimated star-forming dust masses of $M_{DUST}\sim 10^9\,M_\odot$. We have found evidence of a tentative correlation between the gas column densities of the ionized absorbers detected in X-ray (N$_{H_{ion}}$) and $SFR$. Our computed black hole masses are amongst the most massive known.