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Effect of galaxy mergers on star-formation rates

W. J. PearsonKapteyn Astronomical Institute, University of Groningen, Postbus 800, 9700 AV Groningen, The NetherlandsL. WangKapteyn Astronomical Institute, University of Groningen, Postbus 800, 9700 AV Groningen, The NetherlandsM. AlpaslanCenter for Cosmology and Particle Physics, New York University, 726 Broadway, New York, NY 10012, USAI. K. BaldryAstrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead CH41 1LD, UKMaciej BilickiCenter for Theoretical Physics, Polish Academy of Sciences, Al. Lotnikw 32/46, 02-668 Warsaw, PolandM. J. I. BrownSchool of Physics and Astronomy, Monash University, Clayton, Victoria 3800, AustraliaM. W. GrootesNetherlands eScience Center, Science Park 140, 1098 XG Amsterdam, The NetherlandsBenne W. HolwerdaDepartment of Physics and Astronomy, 102 Natural Science Building, University of Louisville, Louisville, KY 40292, USAT. D. KitchingMullard Space Science Laboratory, Dorking RH5 6NT, UKSandor KrukEuropean Space Agency, ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The NetherlandsF. F. S. van der TakKapteyn Astronomical Institute, University of Groningen, Postbus 800, 9700 AV Groningen, The Netherlands

2019en

ABI

Annotatsiya

Context . Galaxy mergers and interactions are an integral part of our basic understanding of how galaxies grow and evolve over time. However, the effect that galaxy mergers have on star-formation rates (SFRs) is contested, with observations of galaxy mergers showing reduced, enhanced, and highly enhanced star formation. Aims . We aim to determine the effect of galaxy mergers on the SFR of galaxies using statistically large samples of galaxies, totalling over 200 000, which is over a large redshift range from 0.0 to 4.0. Methods . We trained and used convolutional neural networks to create binary merger identifications (merger or non-merger) in the SDSS, KiDS, and CANDELS imaging surveys. We then compared the SFR, with the galaxy main sequence subtracted, of the merging and non-merging galaxies to determine what effect, if any, a galaxy merger has on SFR. Results . We find that the SFR of merging galaxies are not significantly different from the SFR of non-merging systems. The changes in the average SFR seen in the star-forming population when a galaxy is merging are small, of the order of a factor of 1.2. However, the higher the SFR is above the galaxy main sequence, the higher the fraction is for galaxy mergers. Conclusions . Galaxy mergers have little effect on the SFR of the majority of merging galaxies compared to the non-merging galaxies. The typical change in SFR is less than 0.1 dex in either direction. Larger changes in SFR can be seen but are less common. The increase in merger fraction as the distance above the galaxy main sequence increases demonstrates that galaxy mergers can induce starbursts.

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DOI: 10.1051/0004-6361/201936337

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