J/A+A/704/A234 KiDS merging galaxies predicted merger times (Pearson+, 2025)
Observationally derived change in star-formation rate as mergers progress.
Pearson W.J., Wang L., Rodriguez-Gomez V., Margalef-Bentabol B.,
Suelves L.E.
<Astron. Astrophys. 704, A234 (2025)>
=2025A&A...704A.234P 2025A&A...704A.234P (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, interacting ; Optical
Keywords: methods: numerical - galaxies: evolution - galaxies: interactions -
galaxies: star formation - galaxies: statistics - galaxies: structure
Abstract:
Galaxy mergers can change the rate at which stars are formed. We can
trace when these changes occur in simulations of galaxy mergers.
However, for observed galaxies we do not know how the star-formation
rate (SFR) evolves along the merger sequence as it is difficult to
probe the time before or after coalescence.
We aim to derive how SFR changes in observed mergers throughout the
merger sequence, from a statistical perspective.
Merger times were estimated for observed galaxy mergers in the Kilo
Degree Survey (KiDS) using a convolutional neural network (CNN). The
CNN was trained on mock KiDS images created using IllustrisTNG data.
The SFRs were derived from spectral energy density fitting to KiDS and
VIKINGs data. To determine the change in SFR for the merging galaxies,
each merging galaxy was matched and compared to ten comparable
non-merging galaxies; matching redshift, stellar mass, and local
density.
Mergers see an increase in SFR for galaxies from 300Myr before the
merger until coalescence, continuing until at least 200Myr after the
merger event. After this, there is a possibility that SFR activity in
the mergers begins to decrease, but we need more data to better
constrain our merger times and SFRs to confirm this. We find that more
galaxies with larger stellar mass (M*) have greater SFR enhancement as
they merge compared to lower M* galaxies. There is no clear trend of
changing SFR enhancement as local density changes, but the least dense
environments have the least SFR enhancement. The increasing SFR
enhancement is likely due to closer proximity of galaxies and the
presence of more close passes as the time before merger approaches
0Myr, with SFR slowing 200Myr after the merger event.
Description:
Predicted merger times for KiDS merging galaxies.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 55 5897 Predicted merger times for KiDS merging galaxies
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See also:
II/347 : KiDS-ESO-DR3 multi-band source catalog (de Jong+, 2017)
II/383 : ESO KiDS-DR5 multi-band source catalog (Wright+ 2024)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 29 A29 --- KiDSDR4 KiDS DR4 identifier
(KiDSDR4_JHHMMSS.sss+DDMMSS.ss)
31- 50 F20.18 --- MergerTimeNorm [0/1] Normalised merger time from CNN
52- 55 I4 Myr MergerTimeMyr [-485/492] Time after merger [Myr]
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Acknowledgements:
From William Pearson, william.pearson(at)ncbj.gov.pl
W.J.P. has been supported by the Polish National Science Center
projects UMO-2020/37/B/ST9/00466 and UMO-2023/51/D/ST9/00147.
L.W. and B.M-B acknowledge funding from the project 'Clash of the
Titans: de- ciphering the enigmatic role of cosmic collisions' (with
project number VI.Vidi.193.113 of the research programme Vidi which is
(partly) financed by the Dutch Research Council (NWO).
L.E.S. was supported by the Estonian Ministry of Education and
Research (grant TK202), Estonian Research Council grant (PRG1006), and
the European Union's Horizon Europe research and innovation programme
(EXCOSM, grant No. 101159513).
The IllustrisTNG simulations were undertaken with compute time awarded
by the Gauss Centre for Supercomputing (GCS) under GCS Large-Scale
Projects GCS- ILLU and GCS-DWAR on the GCS share of the supercomputer
Hazel Hen at the High Performance Computing Center Stuttgart (HLRS),
as well as on the machines of the Max Planck Computing and Data
Facility (MPCDF) in Garching, Germany.
Based on observations made with ESO Telescopes at the La Silla Paranal
Observatory under programme IDs 177.A-3016, 177.A-3017, 177.A-3018 and
179.A- 2004, and on data products produced by the KiDS consortium. The
KiDS production team acknowledges support from: Deutsche
Forschungsgemeinschaft, ERC, NOVA and NWO-M grants; Target; the
University of Padova, and the University Federico II (Naples).
(End) Patricia Vannier [CDS] 27-Oct-2025