  We present a new backward evolution model for galaxies and AGNs in the
infrared (IR). What is new in this model is the separate study of the
evolutionary properties of the different IR populations (i.e. spiral galaxies,
starburst galaxies, low-luminosity AGNs, "unobscured" type 1 AGNs and
"obscured" type 2 AGNs) defined through a detailed analysis of the spectral
energy distributions (SEDs) of large samples of IR selected sources. The
evolutionary parameters have been constrained by means of all the available
observables from surveys in the mid- and far-IR (source counts, redshift and
luminosity distributions, luminosity functions). By decomposing the SEDs
representative of the three AGN classes into three distinct components (a
stellar component emitting most of its power in the optical/near-IR, an AGN
component due to hot dust heated by the central black hole peaking in the
mid-IR, and a starburst component dominating the far-IR spectrum) we have
disentangled the AGN contribution to the monochromatic and total IR luminosity
emitted by the different populations considered in our model from that due to
star-formation activity. We have then obtained an estimate of the total IR
luminosity density (and star-formation density - SFD - produced by IR galaxies)
and the first ever estimate of the black hole mass accretion density (BHAR)
from the IR. The derived evolution of the BHAR is in agreement with estimates
from X-rays, though the BHAR values we derive from IR are slightly higher than
the X-ray ones. Finally, we have simulated source counts, redshift
distributions and SFD and BHAR that we expect to obtain with the future
cosmological Surveys in the mid-/far-IR that will be performed with JWST-MIRI
and SPICA-SAFARI.
