Galaxy-SMBH co-evolution in 2,435 DESI disk galaxies and merger-free BH growth in bulgeless disks

Abstract

We analyse black hole scaling relations for disk-dominated galaxies, and present evidence for secularly driven galaxy-black hole co-evolution. We do this observationally by looking at ``bulgeless'' galaxies, where the lack of a stellar bulge suggests a quiet merger history. We first compose a sample of 2,435 disk-dominated galaxies hosting optical broad line active galactic nuclei (AGN) from DESI data, and find a M_BH--M_* scaling relation of log(M_BH)= − 3.7^+0.3_−0.3 + 1.00^+0.03_−0.03 log(M_*). From these, we identify 546 bulgeless galaxies hosting AGN, a factor of ≳ 5 larger than pre-existing samples, and find they follow the same M_BH--M_* relation as the general disk galaxy sample. Comparing the bulgeless galaxies to those with some bulge component, we find good agreement in the M_BH--M_* relation (within $3 σ$), but disagreement in the M_BH--M_{*, bulge} relation (at >7 σ). This is the opposite of what is expected from merger-driven co-evolution, suggesting secular growth is significant in establishing observed M_BH--M_* scaling relations. Furthermore, in a control sample of early-type galaxies we find tentative evidence of increased AGN luminosity compared to the bulgeless sample, but no statistical difference in black hole mass. This suggests the assumed merger-dominated evolutionary history of early-type galaxies does not lead to significantly increased long-term BH growth. These results support numerous recent observational and theoretical studies which suggest secular processes fuel significant supermassive black hole growth and galaxy-black hole co-evolution.

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BibTeX RIS

BibTeX

@misc{jewell2026galaxysmbh,
  title = {{Galaxy-SMBH co-evolution in 2,435 DESI disk galaxies and merger-free BH growth in bulgeless disks}},
  author = {Sophie M. Jewell and Rebecca J. Smethurst and Chris J. Lintott and Brooke D. Simmons and Ricarda S. Beckmann and Izzy L. Garland and Tobias Géron and Benne W. Holwerda and Karen L. Masters and Ragadeepika Pucha and Ashley Spindler},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.22434},
  eprint = {2609.22434},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.22434},
  note = {CC BY 4.0},
}

RIS

TY  - UNPB
TI  - Galaxy-SMBH co-evolution in 2,435 DESI disk galaxies and merger-free BH growth in bulgeless disks
AU  - Sophie M. Jewell
AU  - Rebecca J. Smethurst
AU  - Chris J. Lintott
AU  - Brooke D. Simmons
AU  - Ricarda S. Beckmann
AU  - Izzy L. Garland
AU  - Tobias Géron
AU  - Benne W. Holwerda
AU  - Karen L. Masters
AU  - Ragadeepika Pucha
AU  - Ashley Spindler
PY  - 2026
DA  - 2026/09/18
PB  - arXiv
DO  - 10.48550/arxiv.2609.22434
UR  - https://arxiv.org/abs/2609.22434
AB  - We analyse black hole scaling relations for disk-dominated galaxies, and present evidence for secularly driven galaxy-black hole co-evolution. We do this observationally by looking at ``bulgeless'' galaxies, where the lack of a stellar bulge suggests a quiet merger history. We first compose a sample of 2,435 disk-dominated galaxies hosting optical broad line active galactic nuclei (AGN) from DESI data, and find a M_BH--M_* scaling relation of log(M_BH)= − 3.7^+0.3_−0.3 + 1.00^+0.03_−0.03 log(M_*). From these, we identify 546 bulgeless galaxies hosting AGN, a factor of ≳ 5 larger than pre-existing samples, and find they follow the same M_BH--M_* relation as the general disk galaxy sample. Comparing the bulgeless galaxies to those with some bulge component, we find good agreement in the M_BH--M_* relation (within $3 σ$), but disagreement in the M_BH--M_*, bulge relation (at >7 σ). This is the opposite of what is expected from merger-driven co-evolution, suggesting secular growth is significant in establishing observed M_BH--M_* scaling relations. Furthermore, in a control sample of early-type galaxies we find tentative evidence of increased AGN luminosity compared to the bulgeless sample, but no statistical difference in black hole mass. This suggests the assumed merger-dominated evolutionary history of early-type galaxies does not lead to significantly increased long-term BH growth. These results support numerous recent observational and theoretical studies which suggest secular processes fuel significant supermassive black hole growth and galaxy-black hole co-evolution.
ER  -

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