Physical origin of the large-scale conformity in the specific star
  formation rates of galaxies
  Two explanations have been put forward to explain the observed conformity
between the colours and specific star formation rates (SFR/$M_*$) of galaxies
on large scales: 1) the formation times of their surrounding dark matter halos
are correlated (commonly referred to as "assembly bias"), 2) gas is heated over
large scales at early times, leading to coherent modulation of cooling and star
formation between well-separated galaxies (commonly referred to as
"pre-heating") . To distinguish between the pre-heating and assembly bias
scenarios, we search for relics of energetic feedback events in the
neighbourhood of central galaxies with different specific star formation rates.
We find a significant excess of very high mass ($\log M_* > 11.3$) galaxies out
to a distance of 2.5 Mpc around low SFR/$M_*$ central galaxies compared to
control samples of higher SFR/$M_*$ central galaxies with the same stellar mass
and redshift. We also find that very massive galaxies in the neighbourhood of
low SFR/$M_*$ galaxies have much higher probability of hosting radio loud
active galactic nuclei. The radio-loud AGN fraction in neighbours with $\log
M_* > 11.3$ is four times higher around passive, non star-forming centrals at
projected distances of 1 Mpc and two times higher at projected distances of 4
Mpc. Finally, we carry out an investigation of conformity effects in the
recently publicly-released Illustris cosmological hydrodynamical simulation,
which includes energetic input both from quasars and from radio mode accretion
onto black holes. We do not find conformity effects of comparable amplitude on
large scales in the simulations and we propose that gas needs to be pushed out
of dark matter halos more efficiently at high redshifts.
