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

We present the quantitative rest-frame B morphological evolution and galaxy merger fraction at 0.2 < z < 1.2 as observed by the All-Wavelength Extended Groth Strip International Survey (AEGIS). We use the Gini coefficient and M sub(20) to identify major mergers and classify galaxy morphology for a volume-limited sample of 3009 galaxies brighter than 0.4L super(*) sub(B), assuming pure luminosity evolution. We find that the merger fraction remains roughly constant at 10% plus or minus 2% for 0.2 < z < 1.2. The fraction of E/S0/Sa galaxies increases from 21% plus or minus 3% at z similar to 1.1 to 44% plus or minus 9% at z similar to 0.3, while the fraction of Sb-Ir galaxies decreases from 64% plus or minus 6% at z similar to 1.1 to 47% similar to 9% at z similar to 0.3. The majority of z < 1.2 Spitzer MIPS 24 mu m sources with L(IR) > 10 super(11) L [unk] are disk galaxies, and only similar to 15% are classified as major merger candidates. Edge-on and dusty disk galaxies (Sb-Ir) are almost a third of the red sequence at z similar to 1.1, while E/S0/Sa make up over 90% of the red sequence at z similar to 0.3. Approximately 2% of our full sample are red mergers. We conclude (1) the merger rate does not evolve strongly between 0.2 < z < 1.2; (2) the decrease in the volume-averaged star formation rate density since z similar to 1 is a result of declining star formation in disk galaxies rather than a disappearing population of major mergers; (3) the build-up of the red sequence at z < 1 can be explained by a doubling in the number of spheroidal galaxies since z similar to 1.2.