Multi-Band and Multi-Messenger Observations of Intermediate-Mass Black Holes

The latest LIGO-Virgo observations hint at a previously unknown population of ‘lite’ intermediate-mass black holes (IMBHs) of about 100 solar masses. In this talk, I will review how this IMBH population opens a new era of “Multi-Band” gravitational-wave astronomy between space-mission LISA and the LIGO-Virgo network on earth. In doing so, I will argue why these multi-band observations are crucial to understanding the origins of IMBHs. I will conclude by reviewing the multi-band, multi-messenger landscape of IMBHs for several emerging gravitational-wave frontiers, such as NASA’s lunar programs and the ESA Voyage 2050 space-mission program.