A relationship of polycyclic aromatic hydrocarbon features with galaxy merger in star-forming galaxies at z < 0.2

Using the AKARI, Wide-field Infrared Survey Explorer (WISE), Infrared Astronomical Satellite (IRAS), Sloan Digital Sky Survey (SDSS) and Hubble Space Telescope (HST) data, we investigated the relation of polycyclic aromatic hydrocarbon (PAH) mass (M-PAH), very small grain mass (M-VSG), big grain mass (M-BG) and stellar mass (M-star) with galaxy merger for 55 star-forming galaxies at redshift z < 0.2. Using the SDSS image at z < 0.1 and the HST image at z > 0.1, we divided the galaxies into merger galaxies and non-merger galaxies with the morphological parameter asymmetry A, and quantified merging stages of galaxies based on the morphological indicators, the second-order momentum of the brightest 20 per cent region M-20 and the Gini coefficient. We find that M-PAH/M-BG of merger galaxies tend to be lower than that of non-merger galaxies and there are no systematic differences of M-VSG/M-BG and M-BG/M-star between merger galaxies and non-merger galaxies. We find that galaxies with very low M-PAH/M-BG seem to be merger galaxies at late stages. These results suggest that PAHs are partly destroyed at late stages of merging processes. Furthermore, we investigated MPAH/MBG variations in radiation field intensity strength G(0) and the emission line ratio of [O I] lambda 6300/H alpha that is a shock tracer for merger galaxies and find that M-PAH/M-BG decreases with increasing both G(0) and [O I]/H alpha. PAH destruction is likely to be caused by two processes: strong radiation fields and large-scale shocks during merging processes of galaxies.