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Durham University

Department of Physics

Staff profile

Publication details for Prof David Alexander

Chen, C.-T.J., Hickox, R.C., Alberts, S., Harrison, C.M., Alexander, D.M., Assef, R., Brodwin, M., Brown, M.J.I., Del Moro, A., Forman, W.R., Gorjian, V., Goulding, A.D., Hainline, K.N., Jones, C., Kochanek, C.S., Murray, S.S., Pope, A., Rovilos, E. & Stern, D. (2015). A Connection between Obscuration and Star Formation in Luminous Quasars. The Astrophysical Journal 802(1): 50.

Author(s) from Durham


We present a measurement of the star formation properties of a uniform sample of mid-IR-selected, optically unobscured, and obscured quasars (QSO1s and QSO2s) in the Boötes survey region. We use a spectral energy distribution analysis for photometric data spanning optical to far-IR wavelengths to separate the active galactic nucleus (AGN) and host galaxy components. We find that when compared to a matched sample of QSO1s, the QSO2s have roughly twice the far-IR detection fractions, far-IR fluxes, and infrared star formation luminosities ($L_{{\rm IR}}^{{\rm SF}}$). Correspondingly, we show that the AGN obscured fraction rises from 0.3 to 0.7 between (4–40) × ${{10}^{11}}{{L}_{\odot }}$. We also find evidence associating X-ray absorption with the presence of far-IR-emitting dust. Overall, these results are consistent with galaxy evolution models in which quasar obscuration is associated with dust-enshrouded starburst galaxies.