We present Hubble Space Telescope NICMOS H -band imaging of 33 ultraluminous infrared galaxies ( ULIRGs ) at z \sim 2 that were selected from the 24 µm catalog of the Spitzer Extragalactic First Look Survey .
The images reveal that at least 17 of the 33 objects are associated with interactions .
Up to one-fifth of the sources in our sample could be minor mergers , whereas only two systems are merging binaries with luminosity ratio \leq 3:1 , which is characteristic of local ULIRGs .
The rest-frame optical luminosities of the sources are of the order 10 ^ { 10 } - 10 ^ { 11 } L _ { \odot } and their effective radii range from 1.4 to 4.9 kpc .
The most compact sources are either those with a strong active nucleus continuum or those with a heavy obscuration in the mid-infrared regime , as determined from Spitzer Infrared Spectrograph data .
The luminosity of the 7.7µm feature produced by polycyclic aromatic hydrocarbon molecules varies significantly among compact systems , whereas it is typically large for extended systems .
A bulge-to-disk decomposition performed for the six brightest ( m _ { H } < 20 ) sources in our sample indicates that they are best fit by disk-like profiles with small or negligible bulges , unlike the bulge-dominated remnants of local ULIRGs .
Our results provide evidence that the interactions associated with ultraluminous infrared activity at z \sim 2 can differ from those at z \sim 0 .