et al. 2007). Accordingly we assign these sources an intrinsic type I or Compton-thin type II SED, extinguished by a dust screen with $A_{\rm{V}} = 4-  27$ mag (as found by Polletta et al. 2008 for obscured quasars). An extinction curve extending into the infrared is taken from McClure (2009). These AGN infrared SED components are normalised using the correlation between 12 micron and hard X-ray emission found by Gandhi et al. (2009), which appears to hold for obscured and unobscured AGN (including Compton-thick sources) and to extend into the quasar regime:

$$\rm{ log L_{\rm{MIR}}} = (-4.37 \pm 3.08) + (1.106 \pm 0.071)\rm{log} L_{\rm{X}},$$

where L$_{\rm{MIR}} = \lambda L_{\rm{\lambda}}$ at 12.3 in . Gaussian scatter of $\sigma = 0.36$ is assumed on the relation.

### Star-formation

There is abundant evidence for ongoing star formation in the host galaxies of radio-quiet AGN and this is likely to dominate the far-infrared SED. The consensus emerging from targeted observations of local Seyferts (Buchanan et al. 2006; Thompson et al. 2009) and studies of more distant samples and cosmological surveys (e.g. Silverman et al. 2009; Hernán-Caballero et al. 2009; Serjeant & Hatziminaoglou 2009) is that the star formation is generally higher in obscured AGN 