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 $z\sim 2$. We have performed deep narrowband imaging surveys in the Subaru/XMM-Newton 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 Hα 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 Hα 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 $M_{\ast }={10}^9$–${10}^{11}{M}_{\odot }$ 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 $z\sim 2$.