Using HST /WFC3 imaging taken as part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey ( CANDELS ) , we examine the role that major galaxy mergers play in triggering active galactic nuclei ( AGN ) activity at z \sim 2 .
Our sample consists of 72 moderate-luminosity ( L _ { X } \sim 10 ^ { 42 - 44 } erg s ^ { -1 } ) AGN at 1.5 < z < 2.5 that are selected using the 4 Msec Chandra observations in the Chandra Deep Field South , the deepest X-ray observations to date .
Employing visual classifications , we have analyzed the rest-frame optical morphologies of the AGN host galaxies and compared them to a mass-matched control sample of 216 non-active galaxies at the same redshift .
We find that most of the AGN reside in disk galaxies ( 51.4 ^ { +5.8 } _ { -5.9 } \% ) , while a smaller percentage are found in spheroids ( 27.8 ^ { +5.8 } _ { -4.6 } \% ) .
Roughly 16.7 ^ { +5.3 } _ { -3.5 } \% of the AGN hosts have highly disturbed morphologies and appear to be involved in a major merger or interaction , while most of the hosts ( 55.6 ^ { +5.6 } _ { -5.9 } \% ) appear relatively relaxed and undisturbed .
These fractions are statistically consistent with the fraction of control galaxies that show similar morphological disturbances .
These results suggest that the hosts of moderate-luminosity AGN are no more likely to be involved in an ongoing merger or interaction relative to non-active galaxies of similar mass at z \sim 2 .
The high disk fraction observed among the AGN hosts also appears to be at odds with predictions that merger-driven accretion should be the dominant AGN fueling mode at z \sim 2 , even at moderate X-ray luminosities .
Although we can not rule out that minor mergers are responsible for triggering these systems , the presence of a large population of relatively undisturbed disk-like hosts suggests that secular processes play a greater role in fueling AGN activity at z \sim 2 than previously thought .