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        The angular clustering of infrared-selected obscured and unobscured quasars

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        Author
        DiPompeo, M. A.
        Myers, A. D.
        Hickox, R. C.
        Geach, J. E.
        Hainline, K. N.
        Attention
        2299/19424
        Abstract
        Recent studies of luminous infrared-selected active galactic nuclei (AGN) suggest that the reddest, most obscured objects display a higher angular clustering amplitude, and thus reside in higher mass darkmatter haloes. This is a direct contradiction to the prediction of the simplest unification-by-orientation models of AGN and quasars. However, clustering measurements depend strongly on the 'mask' that removes low-quality data and describes the sky and selection function.We find that applying a robust, conservative mask to WISE-selected quasars yields a weaker but still significant difference in the bias between obscured and unobscured quasars. These findings are consistent with results from previous Spitzer surveys, and removes any scale dependence of the bias. For obscured quasars with <z> =0.99, we measure a bias of bq = 2.67 ± 0.16, corresponding to a halo mass of log(Mh/M⊙h-1) = 13.3 ± 0.1, while for unobscured sources with <z> = 1.04 we find bq = 2.04 ± 0.17 with a halo mass log(Mh/M⊙h-1) = 12.8 ± 0.1. This improved measurement indicates that WISE-selected obscured quasars reside in haloes only a few times more massive than the haloes of their unobscured counterparts, a reduction in the factor of ∼10 larger halo mass as has been previously reported using WISE-selected samples. Additionally, an abundance matching analysis yields lifetimes for both obscured and unobscured quasar phases on the order of a few 100 Myr (∼1 per cent of the Hubble time) - however, the obscured phase lasts roughly twice as long, in tension with many model predictions.
        Publication date
        2014-08-21
        Published in
        Monthly Notices of the Royal Astronomical Society
        Published version
        https://doi.org/10.1093/mnras/stu1115
        Other links
        http://hdl.handle.net/2299/19424
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