Effect of galaxy mergers on dust masses

Abstract

Dust mass (M$_{Dust}$) is one of the key physical properties of galaxies that track the cold interstellar medium. However, the M$_{Dust}$ in merging galaxies is poorly understood. We aim to derive how the cold dust mass of galaxies is affected by major mergers at low redshifts. M$_{Dust}$ was estimated for approximately 500 major mergers in the North Ecliptic Pole extragalactic field using spectral energy distribution fitting runs with CIGALE, with different dust attenuation and emission models. We also analysed over 12 000 mergers from the SIMBA simulation using its M$_{Dust}$. We matched merging and non-merging systems in stellar mass, redshift, and local density, to enable a comparison of M$_{Dust}$. We then performed a second comparison using a control sample also matched in SFR. AGN host galaxies were then removed, and this matching repeated. Observed mergers have larger M$_{Dust}$ than the non-mergers by up to a factor of 1.82$\pm$0.35, or 1.60$\pm$0.44 without AGN-hosts. When matched by SFR, observed mergers show no significant change in M$_{Dust}$, both when including and excluding AGN-hosts. SIMBA galaxies show similar trends when AGN-hosts are included but there is still an increase in M$_{Dust}$ when matched by SFR. When AGN-hosts are excluded, the SIMBA mergers show smaller M$_{Dust}$ by a factor of 0.98$\pm$0.03, or 0.97$\pm$0.02 when matched in SFR. The higher the mass of a merger, the greater M$_{Dust}$ increase for observations for two of the CIGALE runs, or the smaller the decrease for SIMBA. Observed mergers are typically more dusty than their non-merging counterparts but only because they typically have higher SFRs, regardless of whether they host AGN or not. SIMBA mergers follow observations when AGN hosts are included, but show reduced M$_{Dust}$ when AGN hosts are removed. M$_{Dust}$ in SIMBA is linked to AGN in a way not seen in observations.