Galaxy formation at z > 3 revealed by narrow-band selected [OIII] emission line galaxies

Abstract

We present the physical properties of [OIII] emission line galaxies at z>3 as the tracers of active galaxies at 1Gyr before the peak epoch at z~2. We have performed deep narrow-band imaging surveys in the Subaru/XMM-Newton Deep Survey Field with MOIRCS on the Subaru Telescope and have constructed coherent samples of 34 [OIII] emitters at z=3.2 and 3.6, as well as 107 H$\alpha$ 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 multi-wavelength data and high resolution images by 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 [OIII] emitters at z=3.2 and 3.6 is almost identical to that of the H$\alpha$ 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 $M_* = 10^{9}$-$10^{11} M_{\odot}$ increase their stellar masses significantly by a factor of 10-2. They climb up the main sequence, and their star formation rates also increase a lot as their stellar masses grow. This indicates that star formation activities of galaxies are accelerated from z>3 towards the peak epoch of galaxy formation at z~2.