The evolution of merger fraction of galaxies at z < 0.6 depending on the star formation mode in the AKARI NEP-Wide Field

Abstract

We study the galaxy merger fraction and its dependence on star formation mode in the 5.4 deg(2) of the North Ecliptic Pole-Wide Field. We select 6352 galaxies with AKARI 9 m detections, and identify mergers among them using the Gini coefficient and M-20 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, AKARIm. 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.