Background 'Hum' of The Universe, created by low frequency gravity waves.

[HAL9000]

Background 'Hum' of The Universe, created by low frequency gravity waves generated by supermassive black holes.

After collecting data for more than twelve years the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) announced it may have detected new kinds of gravitational waves caused by colliding supermassive black holes. Professor Chiara Mingarelli of the University of Connecticut tells Roland Pease why this is such an exciting discovery.

One of the things Professor Mingarelli would like to do, is subtract this background hum and see what else can be found.

start at 1 minute to 7 minutes 40 seconds.

Science In Action - Gravitational waves and black holes - BBC Sounds

Gravitational waves from colliding supermassive black holes

www.bbc.co.uk

 

[ferrelhadley]

Supermassive black holes are investigated as possible sources for low-frequency bursts of gravity waves. The event rate for `known' supermassive black holes at intermediate and high redshifts, inferred from the quasar luminosity function is low 0 :1 yr 1 . A number density of gravitational-wave sources comparable to the number density of galaxies inferred from faint galaxy counts is necessary to raise the event rate signicantly above one per year. A space-based interferometer could therefore only see several events per year from supermassive black holes if an additional population of supermassive black holes existed and emitted gravitational waves eciently. These might reside in the population of dwarf galaxies or in a transient population of smal l dark matter haloes that have mostly merged into larger haloes hosting the galaxies seen today, as proposed in a hierarchical cosmogony. In the latter case, event rates could be of order 10 1000 per year due to coalescing supermassive-black-hole binaries formed during the merging process. Event rates could be as high as a few per second if the dark matter in galaxy haloes consists of supermassive black holes in the mass range 10 3 10 6 M , and produced gravitational waves eciently. The proposed space-based gravitational-wave interferometer LISA/SAGITTARIUS should detect most gravitational-wave events involving supermassive black holes above 10 4 M out to redshifts of z 100

https://arxiv.org/pdf/astro-ph/9405032.pdf

So they are proposing far more supermassive black holes than we thought.
I wonder why this is not picked up with things like gravity lensing surveys? Perhaps they do not have the resolution.
Still interesting.