Galaxy merger-driven signatures in massive black hole pair hosts across cosmic time
Abstract
Galaxy mergers can drive gas toward galactic nuclei, enhancing both star formation and black hole accretion in post-merger galaxies. Here we use the IllustrisTNG-50 simulation and two boxes from the BRAHMA simulation suite, all of which adopt different black hole formation models, to characterize merger-associated signatures in candidate massive black hole (MBH)-pair hosts. In all three simulations, we select post-merger galaxies whose progenitors both host MBHs and quantify their enhancements in star formation and black hole accretion relative to matched non-merging controls. In TNG50, we find substantial merger-triggered enhancements in both specific star formation rate (sSFR) and specific black hole accretion rate (sBHAR) at 0 ≤ z < 3.3, reaching ∼ 1.4× and ∼ 1.5−1.7× the controls, respectively. The BRAHMA runs employ more physically motivated seed formation models, seeding BHs in lower-mass galaxies and at higher redshifts than TNG50. In BRAHMA, merger-driven enhancements in sSFR and gas fractions are comparable to those in TNG50 at z ≲ 3.3 and persist to the highest redshifts probed by BRAHMA (z ∼ 6). Despite this, BRAHMA shows no significant merger-driven enhancement in sBHAR across its entire redshift range. In a similar vein, TNG50 pair hosts show an enhanced AGN fraction relative to matched controls, whereas BRAHMA shows only a weak excess among the most rapidly accreting MBHs.
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BibTeX
@misc{satheesh2026galaxy,
title = {{Galaxy merger-driven signatures in massive black hole pair hosts across cosmic time}},
author = {Pranav Satheesh and Aklant K. Bhowmick and Laura Blecha},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.08709},
eprint = {2610.08709},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.08709},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Galaxy merger-driven signatures in massive black hole pair hosts across cosmic time
AU - Pranav Satheesh
AU - Aklant K. Bhowmick
AU - Laura Blecha
PY - 2026
DA - 2026/10/06
PB - arXiv
DO - 10.48550/arxiv.2610.08709
UR - https://arxiv.org/abs/2610.08709
AB - Galaxy mergers can drive gas toward galactic nuclei, enhancing both star formation and black hole accretion in post-merger galaxies. Here we use the IllustrisTNG-50 simulation and two boxes from the BRAHMA simulation suite, all of which adopt different black hole formation models, to characterize merger-associated signatures in candidate massive black hole (MBH)-pair hosts. In all three simulations, we select post-merger galaxies whose progenitors both host MBHs and quantify their enhancements in star formation and black hole accretion relative to matched non-merging controls. In TNG50, we find substantial merger-triggered enhancements in both specific star formation rate (sSFR) and specific black hole accretion rate (sBHAR) at 0 ≤ z < 3.3, reaching ∼ 1.4× and ∼ 1.5−1.7× the controls, respectively. The BRAHMA runs employ more physically motivated seed formation models, seeding BHs in lower-mass galaxies and at higher redshifts than TNG50. In BRAHMA, merger-driven enhancements in sSFR and gas fractions are comparable to those in TNG50 at z ≲ 3.3 and persist to the highest redshifts probed by BRAHMA (z ∼ 6). Despite this, BRAHMA shows no significant merger-driven enhancement in sBHAR across its entire redshift range. In a similar vein, TNG50 pair hosts show an enhanced AGN fraction relative to matched controls, whereas BRAHMA shows only a weak excess among the most rapidly accreting MBHs.
ER -