Evolution of the Galaxy Merger Fraction in the CLAUDS+HSC-SSP Deep Fields
Résumé
We estimate the evolution of the galaxy-galaxy merger fraction for M_\ensuremath★ > 10^10.5M_\ensuremathødot galaxies over 0.25 < z < 1 in the \ensuremath∼18.6 deg^2 deep CLAUDS+HSC-SSP surveys. We do this by training a Random Forest Classifier to identify merger candidates from a host of parametric morphological features, and then visually follow-up likely merger candidates to reach a high-purity, high-completeness merger sample. Correcting for redshift-dependent detection bias, we find that the merger fraction at z = 0 is 1.0% \ensuremath± 0.2%, that the merger fraction evolves as (1 + z)^2.3 \ensuremath± 0.4, and that a typical massive galaxy has undergone \ensuremath∼0.3 major mergers since z = 1. This pilot study illustrates the power of very deep ground-based imaging surveys combined with machine learning to detect and study mergers through the presence of faint, low surface brightness merger features out to at least z \ensuremath∼ 1.