Detectability of intermediate-mass black holes in multiband gravitational wave astronomy

摘要

The direct measurement of gravitational waves is a powerful tool for surveying the population of black holes across the universe. While LIGO has detected black holes as heavy as similar to 50 M-circle dot (ref.(1)), there is not yet unambiguous evidence of black holes in the intermediate mass range of 10(2-5) M-circle dot. Recent electromagnetic observations have hinted towards the existence of intermediate-mass black holes (IMBHs)(2-4); however, their masses remain poorly constrained. Here we argue that multi-band observations by space- and ground-based gravitational wave detectors(5,6) will be able to survey a broad population of IMBHs at cosmological distances. By utilizing general relativistic simulations of merging black holes(7) and state-of-the-art gravitational waveform models(8), we classify three distinct populations of binaries with IMBHs and discuss what can be observed about each. Multiband observations involving the upgraded LIGO detector(9) and the proposed space-mission LISA(10) would detect the inspiral, merger and ring-down of IMBH binaries out to redshift approximate to 2, pushing out to redshift approximate to 5 if next-generation ground-based detectors(11,12) are operational at the same time. To facilitate studies of multiband IMBH sources, we provide analytic relations for the maximum redshift of multiband detectability, as a function of black hole mass, for various detector combinations. Our study paves the way for future work on what can be learned from IMBH observations in the era of multiband gravitational wave astronomy.