Where are you? How fast do you spin? Bayesian parameter estimation on a population of massive black-hole binaries using an inspiral-merger-ringdown waveform model with higher harmonics

The loudest gravitational-wave transient signals that the LISA interferometer will detect are expected to be emitted by the coalescence of massive black-hole binaries (MBHBs) with masses 10⁵ ≤ M ≤ 10⁹ Msun and redshifts 0.5 ≤ z ≤ 3. For these systems, it is important to precisely measure the black-hole masses and spins, and their sky positions. Indeed, constraining masses and spins is crucial to understand the MBHB formation and evolution mechanism, and accurately localizing them can guide the identification of potential electromagnetic counterparts associated to the MBHB merger. In this talk, I will show to what extent LISA can measure the binary parameters of these systems (including masses, spins and sky positions). For this purpose, we perform a parameter estimation study of a large number of MBHBs to understand for which systems we can get the best measurements of their binary parameters. In particular, for each MBHB, we perform a Bayesian parameter estimation study employing the LISA response function, and using a waveform model that includes inspiral, merger, ringdown and the effect of higher harmonics.