Gravitational-wave Measurement of the M BH – M bulge Intrinsic Scatter at High Redshift

@article{matt2026gravitationalwave,
  title = {{Gravitational-wave Measurement of the M BH – M bulge Intrinsic Scatter at High Redshift}},
  author = {Cayenne Matt and Kayhan Gültekin and Gabriella Agazie and Nikita Agarwal and Akash Anumarlapudi and Anne Archibald and Zaven Arzoumanian and Jeremy Baier and Paul Baker and Bence Bécsy and Laura Blecha and Adam Brazier and Paul Brook and Sarah Burke-Spolaor and Rand Burnette and Robin Case and J. Andrew Casey-Clyde and Maria Charisi and Shami Chatterjee and Tyler Cohen and James Cordes and Neil Cornish and Fronefield Crawford and H. Thankful Cromartie and Kathryn Crowter and Megan Decesar and Paul Demorest and Heling Deng and Lankeswar Dey and Timothy Dolch and Graham Doskoch and Elizabeth Ferrara and William Fiore and Emmanuel Fonseca and Gabriel Freedman and Emiko Gardiner and Nate Garver-Daniels and Peter Gentile and Kyle Gersbach and Joseph Glaser and Deborah Good and C. Harris and Jeffrey Hazboun and Ross Jennings and Aaron Johnson and Megan Jones and David Kaplan and Anala Kavumkandathil Sreekumar and Luke Zoltan Kelley and Matthew Kerr and Joey Key and Nima Laal and Michael Lam and William Lamb and Bjorn Larsen and T. Joseph W. Lazio and Natalia Lewandowska and Tingting Liu and Duncan Lorimer and Jing Luo},
  journal = {The Astrophysical Journal},
  year = {2026},
  month = jul,
  doi = {10.3847/1538-4357/ae801e},
  eprint = {2603.11167},
  archivePrefix = {arXiv},
  url = {https://hal.science/hal-05842592v1},
  note = {CC BY},
}

TY  - JOUR
TI  - Gravitational-wave Measurement of the M BH – M bulge Intrinsic Scatter at High Redshift
AU  - Cayenne Matt
AU  - Kayhan Gültekin
AU  - Gabriella Agazie
AU  - Nikita Agarwal
AU  - Akash Anumarlapudi
AU  - Anne Archibald
AU  - Zaven Arzoumanian
AU  - Jeremy Baier
AU  - Paul Baker
AU  - Bence Bécsy
AU  - Laura Blecha
AU  - Adam Brazier
AU  - Paul Brook
AU  - Sarah Burke-Spolaor
AU  - Rand Burnette
AU  - Robin Case
AU  - J. Andrew Casey-Clyde
AU  - Maria Charisi
AU  - Shami Chatterjee
AU  - Tyler Cohen
AU  - James Cordes
AU  - Neil Cornish
AU  - Fronefield Crawford
AU  - H. Thankful Cromartie
AU  - Kathryn Crowter
AU  - Megan Decesar
AU  - Paul Demorest
AU  - Heling Deng
AU  - Lankeswar Dey
AU  - Timothy Dolch
AU  - Graham Doskoch
AU  - Elizabeth Ferrara
AU  - William Fiore
AU  - Emmanuel Fonseca
AU  - Gabriel Freedman
AU  - Emiko Gardiner
AU  - Nate Garver-Daniels
AU  - Peter Gentile
AU  - Kyle Gersbach
AU  - Joseph Glaser
AU  - Deborah Good
AU  - C. Harris
AU  - Jeffrey Hazboun
AU  - Ross Jennings
AU  - Aaron Johnson
AU  - Megan Jones
AU  - David Kaplan
AU  - Anala Kavumkandathil Sreekumar
AU  - Luke Zoltan Kelley
AU  - Matthew Kerr
AU  - Joey Key
AU  - Nima Laal
AU  - Michael Lam
AU  - William Lamb
AU  - Bjorn Larsen
AU  - T. Joseph W. Lazio
AU  - Natalia Lewandowska
AU  - Tingting Liu
AU  - Duncan Lorimer
AU  - Jing Luo
PY  - 2026
DA  - 2026/07/15
JO  - The Astrophysical Journal
DO  - 10.3847/1538-4357/ae801e
UR  - https://hal.science/hal-05842592v1
AB  - The observed gravitational-wave background (GWB) spectrum is higher in amplitude than model predictions by a factor of 2–3. Using a semi-analytic model, we evaluate the effect of a high-scatter supermassive black hole (SMBH) scaling relation ( M BH – M bulge ) on models of the nanohertz GWB. By implementing an intrinsic scatter of the M BH – M bulge relation, which is larger at higher redshift, but matches local observations, we find that the amplitude of GWB models increases to be consistent with the low-frequency end of the GWB spectrum. This amplitude increase is not uniform across frequencies, a strongly evolving scatter preferentially increases the number density of the most massive SMBHs which, in the GWB spectrum, minimizes the strength of the low-frequency turnover. Our models with positively evolving intrinsic scatter can reproduce the electromagnetically observed overmassive SMBHs at 4 < z < 6 without changing the M BH – M bulge normalization though we find that including moderate normalization evolution marginally improves fits to the GWB data. We conclude that the M BH – M bulge relation which best describes the available GWB and electromagnetic data sets has intrinsic scatter that evolves as ε ( z ) = ε 0 + ( 0.56 ± 0.4 ) log 10 ( 1 + z ) and normalization that evolves as α ( z ) = α 0 (1 + z ) 0.84±0.35 . The results of this work imply that the M BH – M bulge relation we see today is not universal throughout cosmic time and that a diversity of seeding models and growth mechanisms may be at play in the early stages of SMBH–galaxy evolution.
SN  - 0004-637X
SN  - 1538-4357
ER  -