Constraining the major merger history of <i>z</i> ∼ 3–9 galaxies using JADES: dominant <i>in situ</i> star formation

ABSTRACT We present a comprehensive analysis of galaxy close-pair fractions and major merger rates to evaluate the importance of mergers in the hierarchical growth of galaxies over cosmic time. This study focuses on the previously poorly understood redshift range of $z \approx 3\!-\!9$ using JADES observations. Our mass-complete sample includes primary galaxies with stellar masses of ${\rm log}(M_\star /{\rm M_\odot }) = [8, 10]$, having major companions (mass ratio $\ge 1/4$) selected by $5\!-\!30$ pkpc projected separation and redshift proximity criteria. Pair fractions are measured using a statistically robust method incorporating photometric redshift posteriors and available spectroscopic data. The pair fraction evolves with redshift and shows dependence on the stellar mass: at ${\rm log}(M_\star /{\rm M_\odot }) = [8.0, 8.5]$ there is an increase up to $z\sim 5\!-\!6$, followed by a turnover, while at higher stellar masses there is a flattening and weak decline with increasing redshift. Similarly, the derived galaxy major merger rate increases and flattens beyond $z \sim 6$ to $2\!-\!8~{\rm Gyr^{-1}}$ per galaxy, showing a weak scaling with stellar mass, driven by the evolution of the galaxy stellar mass function. A comparison between the cumulative mass accretion from major mergers and the mass assembled through star formation indicates that major mergers contribute approximately $3\!-\!13~{{\ \rm per\ cent}}$ to the total mass growth over the studied redshift range, which is in agreement with the ex situ mass fraction estimated from our simple numerical model. These results highlight that major mergers contribute little to the direct stellar mass growth compared to in situ star formation but could still play an indirect role by driving star formation itself.

Authors

Institutions

Publication Details

Journal
Monthly Notices of the Royal Astronomical Society
Published
2025-05-19
DOI
https://doi.org/10.1093/mnras/staf813
Citations
26
Primary Topic
Astronomy and Astrophysical Research
Type
article
Field-Weighted Citation Impact
30.98

Funders

Controls
|||
ALL TIME
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
article

Constraining the major merger history of z ∼ 3–9 galaxies using JADES: dominant in situ star formation

Francesco D’Eugenio, Joris Witstok, Zhiyuan Ji, Santiago Arribas et al.
26 citations
Monthly Notices of the Royal Astronomical Society
Astronomy and Astrophysical Research
30.98
article

Constraining the major merger history of z ∼ 3–9 galaxies using JADES: dominant in situ star formation

Francesco D’Eugenio, Joris Witstok, Zhiyuan Ji, Santiago Arribas, R. Maiolino, Benjamin D. Johnson, Stefano Carniani, Kevin Hainline, Sandro Tacchella, William McClymont, Chris J. Willott, Gareth C. Jones, Charlotte Simmonds, S. Charlot, Christina C. Williams, Pierluigi Rinaldi, Daniel J. Eisenstein, Hannah Übler, Stacey Alberts, Christopher N. A. Willmer, William Baker, Andrew J. Bunker, Brant E. Robertson, Dávid Puskás, Marcia Rieke, Qiao Duan
article en
26 citations

Abstract

ABSTRACT We present a comprehensive analysis of galaxy close-pair fractions and major merger rates to evaluate the importance of mergers in the hierarchical growth of galaxies over cosmic time. This study focuses on the previously poorly understood redshift range of $z \approx 3\!-\!9$ using JADES observations. Our mass-complete sample includes primary galaxies with stellar masses of ${\rm log}(M_\star /{\rm M_\odot }) = [8, 10]$, having major companions (mass ratio $\ge 1/4$) selected by $5\!-\!30$ pkpc projected separation and redshift proximity criteria. Pair fractions are measured using a statistically robust method incorporating photometric redshift posteriors and available spectroscopic data. The pair fraction evolves with redshift and shows dependence on the stellar mass: at ${\rm log}(M_\star /{\rm M_\odot }) = [8.0, 8.5]$ there is an increase up to $z\sim 5\!-\!6$, followed by a turnover, while at higher stellar masses there is a flattening and weak decline with increasing redshift. Similarly, the derived galaxy major merger rate increases and flattens beyond $z \sim 6$ to $2\!-\!8~{\rm Gyr^{-1}}$ per galaxy, showing a weak scaling with stellar mass, driven by the evolution of the galaxy stellar mass function. A comparison between the cumulative mass accretion from major mergers and the mass assembled through star formation indicates that major mergers contribute approximately $3\!-\!13~{{\ \rm per\ cent}}$ to the total mass growth over the studied redshift range, which is in agreement with the ex situ mass fraction estimated from our simple numerical model. These results highlight that major mergers contribute little to the direct stellar mass growth compared to in situ star formation but could still play an indirect role by driving star formation itself.

Monthly Notices of the Royal Astronomical SocietyVol. 540(3)
Herzberg Institute of Astrophysics (CA), University of Copenhagen (DK), Centre National de la Recherche Scientifique (FR), University of Arizona (US), Scuola Normale Superiore (IT), University of California, Santa Cruz (US), University of Cambridge (GB), Institut d'Astrophysique de Paris (FR), Sorbonne Université (FR), University of Oxford (GB), Max Planck Institute for Extraterrestrial Physics (DE), DAWN Center for Independent Living (US), Center for Astrophysics Harvard & Smithsonian (US), Centro de Astrobiología (ES), NSF NOIRLab (US), University College London (GB)
National Science Foundation, National Aeronautics and Space Administration, Villum Fonden, Space Telescope Science Institute, UK Research and Innovation, University of Cambridge, European Commission, National Research Foundation, Danmarks Grundforskningsfond, Nuclear Safety and Security Commission, Ministerio de Ciencia e Innovación, Goddard Space Flight Center, Science and Technology Facilities Council, Agencia Estatal de Investigación
Openalex Percentile: Top 0%
Astronomy and Astrophysical Research
30.98
DOIOpen Access PDFOpenAlex
AI Navigator

Ask Laika to Summarize, Analyze, and Connect papers live on the map.

Summarize Papers & Methodologies

Extract key findings, datasets, and comparative methods across publications.

Benchmark Rankings & Visual Analytics

Rank top research institutions, authors, funders, topics, and journals by Field-Weighted Citation Impact (FWCI) and paper volume with instant charts.

Connect Distant Disciplines

Bridge topological clusters on the map to find hidden collaborative intersections.