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Despite the increasing number of gravitational wave (GW) detections, the astrophysical origin of binary black hole (BBH) mergers remains elusive. A promising formation channel for BBHs is inside accretion discs around supermassive black holes, that power active galactic nuclei (AGN). In this paper, we test for the first time the spatial correlation between observed GW events and AGN. To this end, we assemble all sky catalogues with 1,412 (242) AGN with a bolometric luminosity greater than 1045.5erg s−1 (⁠|$10^{46}\, {\rm erg\, s}^{-1}$|⁠) with spectroscopic redshift of z ≤ 0.3 from the Milliquas catalogue, version 7.7b. These AGN are cross-matched with localization volumes of BBH mergers observed in the same redshift range by the LIGO and Virgo interferometers during their first three observing runs. We find that the fraction of the detected mergers originated in AGN brighter than |$10^{45.5}\, {\rm erg\, s}^{-1}$| (⁠|$10^{46}\, {\rm erg\, s}^{-1}$|⁠) cannot be higher than 0.49 (0.17) at a 95 per cent credibility level. Our upper limits imply a limited BBH merger production efficiency of the brightest AGN, while most or all GW events may still come from lower luminosity ones. Alternatively, the AGN formation path for merging stellar-mass BBHs may be actually overall subdominant in the local Universe. To our knowledge, ours are the first observational constraints on the fractional contribution of the AGN channel to the observed BBH mergers. [ABSTRACT FROM AUTHOR]

The third data release (DR3) of the European Space Agency satellite Gaia provides coordinates, parallaxes, proper motions, and radial velocities for a sample of ∼34 million stars. We use the combined 6D phase space information to search for hypervelocity stars (HVSs), unbound stars accelerated by dynamical processes happening in the Galactic Centre. By looking at the kinematics of Gaia DR3 stars in Galactocentric coordinates and by integrating their orbits in the Galactic potential, we do not identify any HVS candidates with a velocity higher than 700 km s−1 and robustly observed kinematics. Assuming a scenario wherein the interaction between a stellar binary and the massive black hole Sgr A* is responsible for HVS ejections from the Galactic Centre, we derive degenerate limits on the ejection rate of HVSs and the slope of the initial mass function of the primary star among binaries in the Galactic Centre. Our results indicate that the HVS ejection rate is ≲8 × 10−5 yr−1 assuming a Salpeter mass function, and this upper limit becomes progressively smaller for an increasingly top-heavy mass distribution. A fiducial HVS ejection rate of 10−4 yr−1 prefers a mass function slope ≲−2.35, disfavouring previously claimed top-heavy initial mass functions among stars in the Galactic Centre. [ABSTRACT FROM AUTHOR]

The origin of the binary black hole (BBH) mergers detected through gravitational waves (GWs) by the LIGO-Virgo-KAGRA (LVK) collaboration remains debated. One fundamental reason is our ignorance of their host environment, as the typical size of an event's localization volume can easily contain thousands of galaxies. A strategy around this is to exploit statistical approaches to assess the spatial correlation between these mergers and astrophysically motivated host galaxy types, such as active galactic nuclei (AGNs). We use a likelihood ratio method to infer the degree of GW–AGN connection out to z  = 0.2. We simulate BBH mergers whose components' masses are sampled from a realistic distribution of the underlying population of black holes (BHs). Localization volumes for these events are calculated assuming two different interferometric network configurations. These correspond to the configuration of the third (O3) and of the upcoming fourth (O4) LVK observing runs. We conclude that the 13 BBH mergers detected during the third observing run at z ≤ 0.2 are not enough to reject with a 3σ significance the hypothesis according to which there is no connection between GW and AGNs more luminous than |$\approx 10^{44.3}\rm {erg}\ \rm {s}^{-1}$|⁠ , that have number density higher than 10−4.75 Mpc−3. However, 13 detections are enough to reject this no-connection hypothesis when rarer categories of AGNs are considered, with bolometric luminosities greater than |$\approx 10^{45.5}\rm {erg}\ \rm {s}^{-1}$|⁠. We estimate that O4 results will potentially allow us to test fractional contributions to the total BBH merger population from AGNs of any luminosity higher than |$80{{\ \rm per\ cent}}$|⁠. [ABSTRACT FROM AUTHOR]