In article ,
jacobnavia writes:
ALMA sees very far. And at z=4.31, just 1.4 Gy after the supposed
"bang"... it sees a galaxy cluster the mass of the coma cluster...

http://www.eso.org/public/archives/r...2/eso1812a.pdf

Interesting read that article.

Indeed.

Now, wait a minute. If that huge concentration of mass existed 1.4Gy
after the "beginning" we should see an object in the CMB isn't it?

The authors don't say, but I gather the submm flux from the galaxies
overwhelms the CMB signal. The South Pole Telescope, which
discovered the cluster, is primarily a CMB instrument.

If we take the CMB measurements of the Planck satellite, at that
particular point in our horizon we should see this object.

Combined with the signal from the galaxies. Planck presumably saw
what ALMA and SPT saw but with lower angular resolution. The
Herschel/SPIRE map in Extended Data Fig 1 is more interesting.

. And this forming cluster, that
was already a heavyweight at that time, must be a gargantuan object now.

Expected halo mass at z=0 is about 10^15 solar masses, one of the
largest. Not surprising considering this cluster is the strongest
signal in about 1/18 of the sky.

Until a lot of more observations are done, nobody can say
with any satatistical relevance that "the universe" and galaxies were
"younger" at that time.

The galaxy population at high redshift is vastly different from the
local population. In general, high-redshift galaxies are more
compact, lower mass (for constant space density), more gas-rich, and
more irregular than local ones. There is a vast literature on this
subject.

a CLUSTER of [galaxies]... with an incredible mass.

Did you miss Fig 2 (right panel) in the paper? The mass is
consistent with model expectations. The submm flux density is higher
than the model would suggest (Fig 2 left panel), but the model
ignores galaxy interactions. Those raise the star formation rate and
therefore the submm flux density.

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