Evidence of a fraction of LIGO/Virgo/KAGRA events coming from active galactic nuclei

TL;DR

This study investigates the potential link between gravitational-wave sources detected by LIGO/Virgo/KAGRA and active galactic nuclei, providing preliminary evidence that a significant fraction may originate from lower-luminosity or lower-accretion-rate AGNs.

Contribution

It quantifies the fraction of GW events potentially originating from AGNs using spatial correlation analysis, offering new insights into their environmental dependencies.

Findings

Evidence of excess lower-luminosity AGNs around GW events.

Estimated that approximately 29-39% of GW events may come from certain AGN populations.

Correlation unlikely due to random chance, supporting a physical connection.

Abstract

The formation channels of the gravitational-wave (GW) sources detected by LIGO/Virgo/KAGRA (LVK) remain poorly constrained. Active galactic nucleus (AGN) has been proposed as one of the potential hosts, but the fraction of GW events originating from AGNs has not been quantified. Here, we constrain the AGN-origin fraction $f_{\rm agn}$ by analyzing the spatial correlation between GW source localizations ($O1\!-\!O4$a) and AGNs (SDSS DR16). We report preliminary evidence of an excess of lower-luminosity ($10^{44.5} \lesssim L_{\rm bol} \le 10^{45}~\!\mathrm{erg~s}^{-1}$) as well as lower-Eddington ratio ($0.01 \lesssim \lambda_{\rm Edd} \le 0.05$) AGNs around the LVK events, the explanation of which requires $f_{\rm agn} = 0.39^{+0.41}_{-0.32}$ and $0.29^{+0.40}_{-0.25}$ (90\% confidence level) of the LVK events originating from these respective AGN populations. Monte Carlo simulations confirm that this correlation is unlikely to arise from random coincidence, further supported by anomalous variation of the error of $f_{\rm agn}$ with GW event counts. These results support the theoretical speculation that some LVK events come from lower-luminosity or lower-accretion-rate AGNs, offering critical insights into the environmental dependencies of the formation of GW sources.