Nearly all galaxies appear to harbor a supermassive black hole. The origin and properties of initial black hole seeds that grow to produce the detected supermassive black hole population are unconstrained at present, as actively growing seeds are not directly observable near their birth epochs. Nevertheless, some unique signatures of seeding survive and can be discerned in: local scaling relations between black holes and their galaxy hosts at low-masses; in high-redshift X-ray and optical luminosity functions of accreting black holes; and in the total number and mass functions of gravitational wave coalescence events from merging binary black holes. I will describe several of these newly proposed observables that encapsulate information about seeding and permit disentangling the confounding effects of subsequent growth, merging and evolution. With exciting prospects for the availability of multi-wavelength (X-ray, Infra-Red, Optical) and multi-messenger data, we stand to trace the origin of the first black holes.
|Presenter status||INVITED SPEAKER|