The Connection between Mergers and AGN Activity in Simulated and
  Observed Massive Galaxies
  We analyze a suite of $30$ high resolution zoom-in cosmological hydrodynamic
simulations of massive galaxies with stellar masses $M_{\ast} > 10^{10.9}
M_\odot$, with the goal of better understanding merger activity in AGN, AGN
activity in merging systems, SMBH growth during mergers, and the role of gas
content. Using the radiative transfer code \textsc{Powderday}, we generate
HST-WFC3 F160W synthetic observations of redshift $0.5 < z < 3$ central
galaxies, add noise properties similar to the CANDELS survey, and measure
morphological properties from the synthetic images using commonly adopted
non-parametric statistics. We compare the distributions of morphological
properties measured from the synthetic images with a sample of inactive
galaxies and X-ray selected AGN hosts from CANDELS. We study the connection
between mergers and AGN activity in the simulations, the synthetic images, and
the observed CANDELS sample. We find that, in both the simulations and CANDELS,
even the most luminous $(L_{\rm bol} > 10^{45}$ erg s$^{-1})$ AGN in our sample
are no more likely than inactive galaxies $(L_{\rm bol} < 10^{43}$ erg
s$^{-1})$ to be found in merging systems. We also find that AGN activity is not
overall enhanced by mergers, nor enhanced at any specific time in the $1$ Gyr
preceding and following a merger. Even gas rich major mergers (stellar mass
ratio $>$1:4) do not necessarily enhance AGN activity or significantly grow the
central SMBH. We conclude that in the simulated massive galaxies studied here,
mergers are not the primary drivers of AGN.
