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      Galaxy evolution in the post-merger regime I -- Most merger-induced in-situ stellar mass growth happens post-coalescence

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          Abstract

          Galaxy mergers can enhance star formation rates throughout the merger sequence, with this effect peaking around the time of coalescence. However, owing to a lack of information about their time of coalescence, post-mergers could only previously be studied as a single, time-averaged population. We use timescale predictions of post-coalescence galaxies in the UNIONS survey, based on the Multi-Model Merger Identifier deep learning framework (\textsc{Mummi}) that predicts the time elapsed since the last merging event. For the first time, we capture a complete timeline of star formation enhancements due to galaxy mergers by combining these post-merger predictions with data from pre-coalescence galaxy pairs in SDSS. Using a sample of 564 galaxies with M1010M at 0.005<z<0.3 we demonstrate that: 1) galaxy mergers enhance star formation by, on average, up to a factor of two; 2) this enhancement peaks within 500 Myr of coalescence; 3) enhancements continue for up to 1~Gyr after coalescence; and 4) merger-induced star formation significantly contributes to galaxy mass assembly, with galaxies increasing their final stellar masses by, 10% to 20% per merging event, producing on average log(M/M)=9.56+0.130.19 more mass than non-interacting star-forming galaxies solely due to the excess star formation.

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          Author and article information

          Journal
          08 October 2024
          Article
          2410.06356
          7090ebb5-f8a2-4c1d-b27d-9daa9cb067e2

          http://arxiv.org/licenses/nonexclusive-distrib/1.0/

          History
          Custom metadata
          Letter Submitted to MNRAS, 6 pages, 4 figures. For a temporal view of quenching in the post-merger regime see companion paper Ellison et al. 2024
          astro-ph.GA

          Galaxy astrophysics
          Galaxy astrophysics

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