GALAXY FORMATION AT z > 3 REVEALED BY NARROWBAND-SELECTED [O III] EMISSION LINE GALAXIES

We present the physical properties of [O III] emission line galaxies at z > 3 as the tracers of active galaxies at 1 Gyr before the peak epoch at z similar to 2. We have performed deep narrowband imaging surveys in the Subaru/XMMNewton Deep Survey Field with the Multi- object InfraRed Camera and Spectrograph on the Subaru Telescope and have constructed coherent samples of 34 [O III] emitters at z = 3.2 and 3.6, as well as 107 Ha emitters at z = 2.2 and 2.5. We investigate their basic physical quantities, such as stellar masses, star formation rates (SFRs), and sizes, using the publicly available multiwavelength data and high- resolution images from the Hubble Space Telescope. The stellar masses and SFRs show a clear correlation known as the "main sequence" of star-forming galaxies. It is found that the location of the main sequence of the [O III] emitters at z = 3.2 and 3.6 is almost identical to that of the Ha emitters at z = 2.2 and 2.5. Also, we investigate their mass- size relation and find that the relation does not change between the two epochs. When we assume that the star- forming galaxies at z = 3.2 grow simply along the same main sequence down to z = 2.2, galaxies with M-* = 10(9)-10(11)M(circle dot) increase their stellar masses significantly by a factor of 10- 2. They climb up the main sequence, and their SFRs also increase a lot as their stellar masses grow. This indicates that star formation activities of galaxies are accelerated from z > 3 toward the peak epoch of galaxy formation at z similar to 2.