The role of mergers in driving morphological transformation over cosmic time

G. Martin, S. Kaviraj, J. E. G. Devriendt, Y. Dubois, C. Pichon

Research output: Contribution to journalArticlepeer-review

32 Citations (Scopus)
44 Downloads (Pure)


Understanding the processes that trigger morphological transformation is central to understanding how and why the Universe transitions from being disc-dominated at early epochs to having the morphological mix that is observed today. We use Horizon-AGN, a cosmological hydrodynamical simulation, to perform a comprehensive study of the processes that drive morphological change in massive (M*/M > 10 10) galaxies over cosmic time. We show that (1) essentially all the morphological evolution in galaxies that are spheroids at z = 0 is driven by mergers with mass ratios greater than 1: 10; (2) major mergers alone cannot produce today's spheroid population - minor mergers are responsible for a third of all morphological transformation over cosmic time and are its dominant driver after z ~ 1; (3) prograde mergers trigger milder morphological transformation than retrograde mergers - while both types of event produce similar morphological changes at z > 2, the average change due to retrograde mergers is around twice that due to their prograde counterparts at z ~ 0; (4) remnant morphology depends strongly on the gas fraction of a merger, with gas-rich mergers routinely re-growing discs; and (5) at a given stellar mass, discs do not exhibit drastically different merger histories from spheroids - disc survival in mergers is driven by acquisition of cold gas (via cosmological accretion and gas-rich interactions) and a preponderance of prograde mergers in their merger histories.

Original languageEnglish
Pages (from-to)2266–2283
Number of pages18
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Early online date24 Jul 2018
Publication statusPublished - 1 Oct 2018


  • Galaxies: evolution
  • Galaxies: formation
  • Galaxies: highredshift
  • Galaxies: interactions
  • Methods: numerical


Dive into the research topics of 'The role of mergers in driving morphological transformation over cosmic time'. Together they form a unique fingerprint.

Cite this