The Quasar SED Mixing Diagram

Details The Quasar SED Mixing Diagram The Quasar SED Mixing Diagram

May 2011

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21812305h&link_type=abstract

American Astronomical Society, AAS Meeting #218, #123.05; Bulletin of the American Astronomical Society, Vol. 43, 2011

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Scientific paper

We present a useful new diagram for characterizing the quasar-host-reddening mixture for AGN SEDs. This "mixing diagram" is based on a detailed study of 413 X-ray selected Type 1 AGN SEDs from the XMM-COSMOS Survey (Elvis, Hao, et al., 2011). The mixing diagram plots the near-IR (1-3micron) spectral slope against the optical (0.3-1micron) slope to form a generalized 'color-color' diagram. A pure AGN continuum (Elvis et al., 1994, E94) and pure host galaxies are located at clear and distinct positions on the mixing diagram. The lines joining them indicate the fraction of host contribution to each AGN. The reddening vector is almost perpendicular to these mixing lines, and so is easily measured independently.
The mixing diagram shows that 90% of the AGNs lie on mixing curves between the mean E94 AGN SED and a host galaxy, with only modest reddening [E(B-V)=0.1-0.2] (Hao et al., 2011a). Lower luminosity and lower Eddington ratio AGNs have a larger host galaxy fraction, as expected. Optically selected samples (SDSS) have smaller host galaxy fractions. There is some intrinsic scatter around the E94 mean SED.
A substantial minority, 10%, of the XMM-COSMOS AGNs are inconsistent with any AGN+host+reddening mix. These AGNs have weak or non-existent near-IR bumps, suggesting a lack of the hot dust characteristic of AGNs (Hao et al., 2010). A similar fraction of these "hot dust poor" (HDP) quasars are found in the Elvis et al. 1994 (BQS) and Richards et al. 2006 (SDSS) samples (Hao et al., 2011b). The fraction of "hot dust poor" AGNs grows to 20% at z>2 (Hao et al. 2010).
The proposed 'cosmic cycle' of SMBH and galaxy co-evolution (e.g. Hopkins et al., 2006) can be shown as tracks on the mixing diagram. The mixing diagram definition could also be expanded to other wavelengths.

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