The Evolution of Galaxy Mergers and Morphology atz< 1.2 in the Extended Groth Strip

We present the quantitative rest-frame B morphological evolution and galaxymerger fractions at 0.2 < z < 1.2 as observed by the All-wavelength ExtendedGroth Strip International Survey (AEGIS). We use the Gini coefficent and M_20to identify major mergers and classify galaxy morphology for a volume-limitedsample of 3009 galaxies brighter than 0.4 L_B^*, assuming pure luminosityevolution of 1.3 M_B per unit redshift. We find that the merger fractionremains roughly constant at 10 +/- 2% for 0.2 < z < 1.2. The fraction ofE/S0/Sa increases from 21+/- 3% at z ~ 1.1 to 44 +/- 9% at z ~ 0.3, while thefraction of Sb-Ir decreases from 64 +/- 6% at z ~ 1.1 to 47 +/- 9% at z ~ 0.3.The majority of z < 1.2 Spitzer MIPS 24 micron sources with L(IR) > 10^11 L_sunare disk galaxies, and only ~ 15% are classified as major merger candidates.Edge-on and dusty disk galaxies (Sb-Ir) are almost a third of the red sequenceat z ~ 1.1, while E/S0/Sa makeup over 90% of the red sequence at z ~ 0.3.Approximately 2% of our full sample are red mergers. We conclude (1) the galaxymerger rate does not evolve strongly between 0.2 < z < 1.2; (2) the decrease inthe volume-averaged star-formation rate density since z ~ 1 is a result ofdeclining star-formation in disk galaxies rather than a disappearing populationof major mergers; (3) the build-up of the red sequence at z < 1 can beexplained by a doubling in the number of spheroidal galaxies since z ~ 1.2.