In article ,
jacobnavia writes:
A team of astronomers have conducted a search for distant super massive
black holes and they have found 83 of them. See:

https://www.princeton.edu/news/2019/...early-universe

The refereed paper -- open access -- is at
https://iopscience.iop.org/article/1...57/aaee7a/meta

What is interesting is that contrary to the expectations of the big bang
hypothesis, the density of those beasts is not at all higher than now.

Why do you think that's the expectation of Big Bang theory?

Fig 13 of the paper shows the rise in QSO number density from z=6,
the epoch the new observations address, to z=4. Other papers show
the number density continues to rise to about z=2, then falls.

According to BB theory, the neutral hydrogen was reionized after the
"dark ages". Where would the huge amount of energy necessary for
reionization come from?

The standard expectation is hot stars in low-mass galaxies. Fig 12
of the paper shows the z=6 luminosity function of Lyman-break
galaxies (LBGs). JWST should do even better.

The standard answer was that massive black holes would provide it...

When was that ever the standard answer?

apparently the density of black holes 13 Gy ago was no higher than now.

What does the comparison with "now" have anything to do with
reionization? The intergalactic medium is ionized now, so something
had to have done that. We know in fact that it occurred at redshifts
of something like 8 to 5 or so.

We are at the limit of current scopes. I am confident that in a few
years we will find even farther away quasars.

No doubt. JWST will find some, but its field of view is tiny. LSST
might do better, and the large ground-based telescopes will make a
contribution.

[[Mod. note --
2. Did Matsuoka et al discuss the space density of such quasars? I don't
see anything about that in a quick skim of their preprint.

See Fig 10 or Table 4 of the paper I linked above.

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