Statistical evidence for massive black hole recoils in active galactic nuclei

Fuente: arXiv
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Auteurs principaux: Bécsy, Bence, Raffai, Peter, Haiman, Zoltán, Budai, Andor, Frei, Zsolt
Format: Preprint
Publié: 2026
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author Bécsy, Bence
Raffai, Peter
Haiman, Zoltán
Budai, Andor
Frei, Zsolt
author_facet Bécsy, Bence
Raffai, Peter
Haiman, Zoltán
Budai, Andor
Frei, Zsolt
contents We search for a population-level signature of gravitational-wave recoiling supermassive black holes: a positive correlation between dust obscuration and the magnitude of the line-of-sight velocity offset of broad emission lines relative to the host. Using the SDSS DR16 quasar catalogue, we estimate the velocity offset, $Δv$, as the difference between the broad H$β$ redshift and a noise-weighted redshift from narrow lines ([O III] 5007, [O II] 3728, and Ca II 3934). We adopt the redshift-relative colour excess $Δ(g-i)$ as a proxy for dust column density. Analysing $\sim10^{5}$ quasars that meet basic spectral quality requirements, we find a modest but highly significant positive correlation between $|Δv|$ and $Δ(g-i)$ (Spearman $r\simeq0.12$ and Pearson $r\simeq0.13$, with $p\ll10^{-10}$ in both cases). The fraction of highly obscured quasars increases with $|Δv|$, indicating that the correlation is driven by a dust-reddened subpopulation. The result is robust to the choice of minimum $|Δv|$ threshold and to the line redshift estimator (peak vs. centroid). As expected, the correlation is largely absent when velocity offsets are computed between narrow emission lines. We find systematic differences between redshifted and blueshifted subsamples, which may point to residual velocity biases or additional physical effects (e.g. winds, inflows, orientation-dependent obscuration, or asymmetric broad-line regions). Recoiling massive black holes provide a natural explanation for the observed correlation, but alternative scenarios should be explored. If confirmed, this would enable population-level constraints on massive black hole merger rates, recoil dynamics, and active galactic nuclei disc properties.
format Preprint
id arxiv_https___arxiv_org_abs_2605_04781
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Statistical evidence for massive black hole recoils in active galactic nuclei
Bécsy, Bence
Raffai, Peter
Haiman, Zoltán
Budai, Andor
Frei, Zsolt
Astrophysics of Galaxies
We search for a population-level signature of gravitational-wave recoiling supermassive black holes: a positive correlation between dust obscuration and the magnitude of the line-of-sight velocity offset of broad emission lines relative to the host. Using the SDSS DR16 quasar catalogue, we estimate the velocity offset, $Δv$, as the difference between the broad H$β$ redshift and a noise-weighted redshift from narrow lines ([O III] 5007, [O II] 3728, and Ca II 3934). We adopt the redshift-relative colour excess $Δ(g-i)$ as a proxy for dust column density. Analysing $\sim10^{5}$ quasars that meet basic spectral quality requirements, we find a modest but highly significant positive correlation between $|Δv|$ and $Δ(g-i)$ (Spearman $r\simeq0.12$ and Pearson $r\simeq0.13$, with $p\ll10^{-10}$ in both cases). The fraction of highly obscured quasars increases with $|Δv|$, indicating that the correlation is driven by a dust-reddened subpopulation. The result is robust to the choice of minimum $|Δv|$ threshold and to the line redshift estimator (peak vs. centroid). As expected, the correlation is largely absent when velocity offsets are computed between narrow emission lines. We find systematic differences between redshifted and blueshifted subsamples, which may point to residual velocity biases or additional physical effects (e.g. winds, inflows, orientation-dependent obscuration, or asymmetric broad-line regions). Recoiling massive black holes provide a natural explanation for the observed correlation, but alternative scenarios should be explored. If confirmed, this would enable population-level constraints on massive black hole merger rates, recoil dynamics, and active galactic nuclei disc properties.
title Statistical evidence for massive black hole recoils in active galactic nuclei
topic Astrophysics of Galaxies
url https://arxiv.org/abs/2605.04781