Realistic event rates for detection of supermassive black hole coalescence by LISA

Abstract

The gravitational waves generated during supermassive black hole (SMBH) coalescence are prime candidates for detection by the satellite LISA. We use the extended Press-Schechter formalism combined with empirically motivated estimates for the SMBH-dark matter halo mass relation and SMBH occupation fraction to estimate the maximum coalescence rate for major SMBH mergers. Assuming efficient binary coalescence, and guided by the lowest nuclear black hole mass inferred in local galactic bulges and nearby low-luminosity active galactic nuclei (≈105 M⊙), we predict approximately 15 detections per year at a signal-to-noise ratio greater than 5, in each of the inspiral and ringdown phases. Rare coalescences between SMBHs having masses in excess of 107 M⊙ will be more readily detected via gravitational waves from the ringdown phase.