The PEP survey: clustering of infrared-selected galaxies and structure
  formation at z~2 in the GOODS South
  ABRIDGED-This paper presents the first direct estimate of the 3D clustering
properties of far-infrared sources up to z~3. This has been possible thanks to
the Pacs Evolutionary Probe (PEP) survey of the GOODS South field performed
with the PACS instrument onboard the Herschel Satellite. An analysis of the
two-point correlation function over the whole redshift range spanned by the
data reports for the correlation length, r_0~6.3 Mpc and r_0~6.7 Mpc,
respectively at 100um and 160um, corresponding to dark matter halo masses
M>~10^{12.4} M_sun. Objects at z~2 instead seem to be more strongly clustered,
with r_0~19 Mpc and r_0~17 Mpc in the two considered PACS channels. This
dramatic increase of the correlation length between z~1 and z~2 is connected
with the presence of a wide, M>~10^{14} M_sun, filamentary structure which
includes more than 50% of the sources detected at z~2. An investigation of the
properties of such sources indicates the possibility for boosted star-forming
activity in those which reside within the overdense environment with respect of
more isolated galaxies found in the same redshift range. Lastly, we also
present our results on the evolution of the relationship between luminous and
dark matter in star-forming galaxies between z~1 and z~2. We find that the
increase of (average) stellar mass in galaxies <M*> between z~1 and z~2 is
about a factor 10 lower than that of the dark matter haloes hosting such
objects (<M*>[z~1]/<M*>[z~2] ~ 0.4 vs M_{halo}[z~1]/M_{halo}[z~2] ~ 0.04). Our
findings agree with the evolutionary picture of downsizing whereby massive
galaxies at z~2 were more actively forming stars than their z~1 counterparts,
while at the same time contained a lower fraction of their mass in the form of
luminous matter.
