The evolution of merger fraction of galaxies at z AKARI NEP-Wide Field

ABSTRACT We study the galaxy merger fraction and its dependence on star formation mode in the 5.4 deg2 of the North Ecliptic Pole-Wide Field. We select 6352 galaxies with AKARI 9 µm detections, and identify mergers among them using the Gini coefficient and M20 derived from the Subaru/Hyper Suprime-Cam (HSC) optical images. We obtain the total infrared luminosity and star formation rate of galaxies using the spectral energy distribution templates based on one band, AKARI 9 µm. We classify galaxies into three different star formation modes (i.e. starbursts, main-sequence, and quiescent galaxies) and calculate the merger fractions for each. We find that the merger fractions of galaxies increase with redshift at z < 0.6. The merger fractions of starbursts are higher than those of main-sequence and quiescent galaxies in all redshift bins. We also examine the merger fractions of far-infrared-detected galaxies that have at least one detection from Herschel/Spectral and Photometric Imaging Receiver (SPIRE). We find that Herschel-detected galaxies have higher merger fraction compared to non-Herschel-detected galaxies, and both Herschel-detected and non-Herschel-detected galaxies show clearly different merger fractions depending on the star formation modes.