Formation of the first supermassive black holes

5 problems

• What fraction of dwarf galaxies host intermediate-mass black holes?

  Open

  Black holes between a hundred and a hundred thousand solar masses (intermediate-mass black holes) should be leftovers of the seeds that grew into giant black holes. How many small galaxies and star clusters contain one today records which kind of seed was common.

• What are the compact red sources (little red dots) found by JWST?

  Contested

  JWST found many tiny, very red objects in the young universe that show signs of a growing black hole but emit almost no X-rays and little hot dust. Whether they are black holes wrapped in dense gas, giant stars, or something else is unknown.

• Are early black holes too massive for their host galaxies?

  Contested

  In nearby galaxies a central black hole weighs about a thousandth of the galaxy's stars, but standard estimates for early JWST black holes give ten to a hundred times more. These estimates may be wrong if dense gas widens the spectral lines used to weigh them.

• Were the first black hole seeds light or heavy?

  Open

  The first black holes could have started as remnants of the first stars (tens to hundreds of solar masses) or as gas clouds collapsing directly into black holes of 10,000 to a million solar masses. Which happened sets everything that followed.

• Can early black holes sustain accretion above the Eddington limit?

  Open

  A black hole normally cannot swallow gas faster than a limit set by the outward push of the light the infalling gas emits (the Eddington limit). Growing a billion-solar-mass black hole within 700 million years from a small seed seems to need this limit to be exceeded for a long time.