2009/12/08 by Jennifer M. Lotz, Patrik Jonsson, Patrik Jönsson +3 · 244 citations
Computer Science · Physics and Astronomy · #Adaptive optics and wavefront sensing #Advanced Vision and Imaging #Astronomy #Astrophysics #Asymmetry #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy formation and evolution #Galaxy merger #Mass ratio #Physics #astro-ph.CO
paper · pdf · doi:10.1111/j.1365-2966.2010.16268.x
published in Monthly Notices of the Royal Astronomical Society 404(2), 575-589 (Oxford University Press) · 16 pages; resubmitted to MNRAS
arxiv created 2009/12/08 · openalex publication_date 2010/04/16 · arxiv updated 2015/05/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The majority of galaxy mergers are expected to be minor mergers. The observational signatures of minor mergers are not well understood; thus, there exist few constraints on the minor merger rate. This paper seeks to address this gap in our understanding by determining if and when minor mergers exhibit disturbed morphologies and how they differ from the morphology of major mergers. We simulate a series of unequal-mass moderate gas-fraction disc galaxy mergers. With the resulting g-band images, we determine how the time-scale for identifying galaxy mergers via projected separation and quantitative morphology (the Gini coefficient G, asymmetry A and the second-order moment of the brightest 20 per cent of the light M20) depends on the merger mass ratio, relative orientations and orbital parameters. We find that G−M20 is as sensitive to 9:1 baryonic mass ratio mergers as 1:1 mergers, with observability time-scales of ∼0.2–0.4 Gyr. In contrast, asymmetry finds mergers with baryonic mass ratios between 4:1 and 1:1 (assuming local disc galaxy gas fractions). Asymmetry time-scales for moderate gas-fraction major disc mergers are ∼0.2–0.4 Gyr and less than 0.06 Gyr for moderate gas-fraction minor mergers. The relative orientations and orbits have little effect on the time-scales for morphological disturbances. Observational studies of close pairs often select major mergers by choosing paired galaxies with similar luminosities and/or stellar masses. Therefore, the various ways of finding galaxy mergers (G−M20, A, close pairs) are sensitive to galaxy mergers of different mass ratios. By comparing the frequency of mergers selected by different techniques, one may place empirical constraints on the major and minor galaxy merger rates.