There are more hiding supermassive black holes in the universe. Than we expected.

"Artistic illustration of the thick dust torus surrounding a supermassive black holes and its accretion disks. Credit: ESA / V. Beckmann (NASA-GSFC)"  (ScitechDaily, NASA Unveils a Hidden Universe of Supermassive Black Holes)

"By combining data from NASA’s IRAS and NuSTAR telescopes, scientists have uncovered more hidden supermassive black holes than earlier estimates suggested." (ScitechDaily, NASA Unveils a Hidden Universe of Supermassive Black Holes)

In all spiral galaxies is a supermassive back hole. The spiral structure can form only if there is some mass center. The most dominating black hole in the Milky Way is Sgr A*. That black hole forms the mass center that forms a spiral galaxy around it. The supermassive black hole is the monster, that creates a galaxy around it. 

The mass of those black holes is higher than the galaxy that we see. And that's why they will pull the whirl that we see as the beautiful spiral galaxy around them. Some galaxies like the Milky Way have more than one supermassive black hole inside them. And that tells about the cosmic collisions between galaxies.

The supermassive black hole sees the born of the galaxy. And it sees the end of the galaxy. When another galaxy or quasar travels to another galaxy and its supermassive black hole it can push and pull the material away from around the galaxy. The relativistic jet of the quasar pushes material from around them. 

It's possible. Supermassive black holes in galaxies or quasars pull almost all material from around them. In the case of galaxies like the Milky Way, the supermassive black hole pulls the entire galaxy inside it. But before that, the Andromeda galaxy impacts our galaxy. 

The supermassive black hole. That is in the cosmic bubble or very thin material area the black hole turns silent. Things like black hole acceleration disks form when a black hole pulls material inside it. 

The silent black hole forms a weak acceleration disk around it. And that makes it hard to see that thing. Also, bright objects near that black hole can cover even large supermassive black holes. 

So, if the supermassive-class black hole can hide in the universe. It's possible that also stellar- and theoretical sub-stellar mass black holes can turn silent. That means. Those black holes can be invisible to observers because they have so weak acceleration disks. Sometimes astronomers say that maybe Planet X is a black hole that lurks in our solar system. 

In some other models, the dark matter is explained as small black holes. Those black holes can form when material gets in the black hole's relativistic jets. Or when some supernova or kilonova sends its shockwave. That thing can push particles into a form called singularity. That means it's possible that. Black holes form other black holes. So, the small mass black holes can still form in the universe. When massive energy presses planets and other objects into a singularity. 

https://scitechdaily.com/nasa-unveils-a-hidden-universe-of-supermassive-black-holes/

https://en.wikipedia.org/wiki/Sagittarius_A*