  We use deep 70, 100 and 160 um observations taken with PACS, the
Photodetector Array Camera and Spectrometer on board of Herschel, as part of
the PACS Evolutionary Probe (PEP) guaranteed time, to study the relation
between star formation rate and environment at redshift ~ 1 in the GOODS-S and
GOODS-N fields. We use the SDSS spectroscopic catalog to build the local analog
and study the evolution of the star formation activity dependence on the
environment. At z ~ 1 we observe a reversal of the relation between star
formation rate and local density, confirming the results based on Spitzer 24 um
data. However, due to the high accuracy provided by PACS in measuring the star
formation rate also for AGN hosts, we identify in this class of objects the
cause for the reversal of the density-SFR relation. Indeed, AGN hosts favor
high stellar masses, dense regions and high star formation rates. Without the
AGN contribution the relation flattens consistently with respect to the local
analog in the same range of star formation rates. As in the local universe, the
specific star formation rate anti-correlates with the density. This is due to
mass segregation both at high and low redshift. The contribution of AGN hosts
does not affect this anti-correlation, since AGN hosts exhibit the same
specific star formation rate as star forming galaxies at the same mass. The
same global trends and AGN contribution is observed once the relations are
studied per morphological type. We study the specific star formation rate vs
stellar mass relation in three density regimes. Our data provides an indication
that at M/M_{\odot} > 10^{11} the mean specific star formation rate tends to be
higher at higher density, while the opposite trend is observed in the local
SDSS star forming sample.
