  Studying the coupling between the energy output produced by the central
quasar and the host galaxy is fundamental to fully understand galaxy evolution.
Quasar feedback is indeed supposed to dramatically affect the galaxy properties
by depositing large amounts of energy and momentum into the ISM. In order to
gain further insights on this process, we study the SEDs of sources at the
brightest end of the quasar luminosity function, for which the feedback
mechanism is supposed to be at its maximum. We model the rest-frame UV-to-FIR
SEDs of 16 WISE-SDSS Selected Hyper-luminous (WISSH) quasars at 1.8 < z < 4.6
disentangling the different emission components and deriving physical
parameters of both the nuclear component and the host galaxy. We also use a
radiative transfer code to account for the contribution of the quasar-related
emission to the FIR fluxes. Most SEDs are well described by a standard
combination of accretion disk+torus and cold dust emission. However, about 30%
of them require an additional emission component in the NIR, with temperatures
peaking at 750K, which indicates the presence of a hotter dust component in
these powerful quasars. We measure extreme values of both AGN bolometric
luminosity (LBOL > 10^47 erg/s) and SFR (up to 2000 Msun/yr). A new relation
between quasar and star-formation luminosity is derived (LSF propto
LQSO^(0.73)) by combining several Herschel-detected quasar samples from z=0 to
4. Future observations will be crucial to measure the molecular gas content in
these systems, probe the impact between quasar-driven outflows and on-going
star-formation, and reveal the presence of merger signatures in their host
galaxies.
