measurement of the cosmic IR background at 100 $\micron$ which is $14.4\pm6.3$ nW m$^{-2}$ sr$^{-1}$ or equivalently $0.48\pm0.21$ MJy sr$^{-1}$ (Dole et al. 2006), then we can estimate that the fractional contribution of the CIB to the 100 $\micron$ maps in the HeLMS, HeRS, [*XMM*]{}-LSS, Boötes and Lockman-SWIRE field is 16%, 17%, 21%, 34% and 44%, respectively.

SDSS DR7 and SDSS-III DR9 QSOs
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For our cross-correlation analysis, we use quasars from both the SDSS DR7 (Abazajian et al. 2009) and the SDSS-III DR9 (Ahn et al. 2012) spectroscopic surveys.

### SDSS DR7 Quasars

The spectroscopic SDSS DR7 quasar catalogue (DR7Q; Schneider et al. 2010; Shen et al. 2010) contains 105,783 spectroscopically confirmed quasars with $i$-band absolute magnitude $M_i<-22.0$ and $0.065<z<5.46$ over an area of 9,380 deg$^2$. It is the culmination of the SDSS-I and SDSS-II quasar surveys. The quasar target selection is described in detail by Richards et al. (2002). Quasar candidates are selected based on their fluxes and colors in SDSS bands. At low-redshift, $z\lesssim3$, quasar targets are selected based on their location in $ugri$-color space and at high-redshift, $z\gtrsim3$, targets are selected from $griz$-color space. Quasar candidates passing the $ugri$-color selection are selected to a flux limit 