paper

Galaxy fields of LISA massive black hole mergers in a simulated Universe

arXiv:2207.10683 · doi:10.1093/mnras/stad058

Abstract

LISA will extend the search for gravitational waves (GWs) at mHz where loud signals from coalescing binary black holes of are expected. Depending on their mass and luminosity distance, the uncertainty in the LISA sky-localization decreases from hundreds of deg during the inspiral phase to fractions of a deg after the merger. By using the semi-analytical model L-Galaxies applied to the Millennium-I merger trees, we generate a simulated Universe to identify the hosts of coalescing binaries with total mass of , and , and varying mass ratio. We find that, even at the time of merger, the number of galaxies around the LISA sources is too large () to allow direct host identification. However, if an X-ray counterpart is associated to the GW sources at , all LISA fields at merger are populated by AGNs emitting above . For sources at higher redshifts, the poorer sky-localization causes this number to increase up to . Archival data from eRosita will allow discarding of these AGNs, being too shallow to detect the dim X-ray luminosity of the GW sources. Inspiralling binaries in an active phase with masses at can be detected, as early as hours before the merger, by future X-ray observatories in less than a few minutes. For these systems, AGNs are within the LISA sky-localization area. Finally, the LISA-Taiji network would guarantee the identification of an X-ray counterpart hours before merger for all binaries at .

arXiv comment25 pages, 14 Figures, To be submitted to MNRAS

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