http://www.space.com/scienceastronomy/091106-earliest-galaxies-univer...

posted: 06 November 2009
01:04 pm ET

A new survey has found 22 of the earliest galaxies to form in the
universe, confirming the age of one at just 787 million years after
the theoretical Big Bang.

These and other galaxies from the universe's childhood could help shed
light on the conditions that governed the early universe.

With recent technological advances, astronomers have been able to
observe more of the so-called reionization era, the farthest back in
time that astronomers can observe.

Universe's first light

For the first few hundred thousand years after the Big Bang (which
took place about 13.7 billion years ago), the universe was a hot,
murky mess, with no light radiating out. Because there is no residual
light from that early epoch, scientists can't observe any traces of
it.

But about 400,000 years after the Big Bang, temperatures in the
universe cooled, electrons and protons joined to form neutral hydrogen
(meaning it had no charge), and the murk cleared. Some time before 1
billion years after the Big Bang, neutral hydrogen began to form stars
in the first galaxies, which radiated energy and changed the hydrogen
back to being ionized, or charged. This was what astronomers call the
reionization period.

But while astronomers know that this period was over by about the time
the universe was 1 billion years old, they don't know exactly when it
began — when the first stars and galaxies began to illuminate the
universe. They also don't know whether reionization started gradually
or instantly.

To help answer this question a team of astronomers led by Masami Ouchi
of the Carnegie Observatories used a technique for finding some of the
early, extremely distant galaxies.

"We look for 'dropout' galaxies," Ouchi said. "We use progressively
redder filters that reveal increasing wavelengths of light and watch
which galaxies disappear from or 'dropout' of images made using those
filters."

Dropout galaxies

The specific wavelengths of light at which the 'dropout' galaxies
appear can tell astronomer's their distance and age.

Ouchi and his colleagues studied an area over 100 times larger than
any previous such study and so had a larger sample of galaxies.

"Plus, we were able to confirm one galaxy's age," Ouchi said. "Since
all the galaxies were found using the same dropout technique, they are
likely to be the same age."

The team's observations were made from 2006 to 2009 with the
wide-field camera of the 8.3-meter Subaru Telescope in Hawaii.

Ouchi and his team compared their observations with those from other
studies looked at the rates of star formation, which can be gleaned
from data on the density and brightness of galaxies, and found that
they were dramatically lower from 800 millions years to about one
billion years after the Big Bang, than thereafter.

Accordingly, they calculated that the rate of ionization would be very
slow during this early time, because of this low star-formation rate.

"We were really surprised that the rate of ionization seems so low,
which would constitute a contradiction with the claim of NASA's WMAP
satellite. It concluded that reionization started no later than 600
million years after the Big Bang," Ouchi said.

"We think this riddle might be explained by more efficient ionizing
photon production rates in early galaxies," he added. "The formation
of massive stars may have been much more vigorous than in today's
galaxies. Fewer, massive stars produce more ionizing photons than many
smaller stars."

Ouchi's findings will be detailed in a December issue of the
Astrophysical Journal.

Bob C.

Of course this gets creationists all riled up.  I guess they
want proof in the form of an ancient document written by
the "Big Banger".

Actually, all it is is circumstantial evidence.  Unbeknownst
to creationists, we actually KILL people in the US based
on circumstantial evidence, an uncivilized activity in which
I'll bet they participate.

Sorry... ;-)

Bob C.

And I agree.  It kills people.

Bob C.

We should eventually be able to observe the cosmic neutrino and
gravitational wave backgrounds, which also come from way before
the CMBR, though it will take a while for out technology to get
good enough to see these.

 While it would be ridiculous for me to claim that I understand
 the theoretical model(s?) you are referring to, I have spent my
 entire life watching this theory evolve, and what I have seen
 has not given me confidence that it makes any sense.

 The idea of an essentially infinitely dense starting condition
 in an expanding space/time has been around for as long as I can
 remember so it must have been dreamt up in the late 50s.

 Why was space/time expanding? - mostly one just heard dogmatic
 assertions that to ask what was going on before was meaningless:
 There was no time or space before the big-bang.  Since time
 (whatever else it is) is the measure of changing events, this
 amounted to an assertion that there were no events before
 the Big-Bang which is obvious nonsense.  We got similar
 nonsense about what was going on outside our universe: nothing,
 there just wasn't anything there.  I could accept: probably not
 accessible, and almost certainly not 3+1 dimensions, but: not
 there?  Just silly.

 I call this initial hypothetical dense expanding state, the first
 call to the tooth fairy - and I don't have all that much trouble
 with it; after all, something started what we see, and in the
 absence of a better idea, why not credit the tooth-fairy?

 Then somebody noticed that the CMBR was too smooth across the sky
 to be explained by a simple expansion from an infinitely dense
 hypothetical state, so up popped the inflation model.  How does
 that work?: well sometime within the first "hour" (or minute or
 second or fraction thereof) of our universe's existence it
 expanded at a rate vastly exceeding the speed of light (oddly
 similar to a claim regularly made by creationists) and then it
 abruptly stopped expanding.  Why did the expansion start?  What
 fundamental principle explains why it stopped?  Why did
 expansion decelerate till 5 billion years ago and then start
 accelerating again?  I haven't heard a hint of an explanation in
 terms of even hypothetical underlying principles.  Do you know
 of such principles?

 I call inflation the second call to the tooth-fairy.  I think
 the tooth-fairy is being over worked here, and it just is NOT
 fair!  She should have AT LEAST the same labor rights
 protections as is granted to children.

 To add to my suspicions, I remember following the release of
 progressively more detailed limits to the variation in the CMBR
 across the sky during the 90's - and while I had no
 understanding at all of what the numbers meant, I do recall
 increasing cries of anguish from cosmologists since the
 variation was so small it was going to make explaining how stars
 formed within the first 3 billion years almost impossible.
 Then when the final numbers came out there was nothing but
 silence - all the problems just seemed to disappear.

 Well, maybe as you have stated there is a good consisted
 theoretical model out there, but I've been hearing that for at
 least 30 years - of models which have obviously been shown to
 be false.  Who predicted dark matter till the observations
 required it?  From where I sit it looks like somebody would
 have come up with *some* model which validated those two calls
 to the tooth fairy no matter how the observational numbers had
 come up.

 Well, it all looks like gerrymandering to me. Let me stress
 that I have NOTHING against the Tooth Fairy, but I say she
 deserves to be selected in a fair and unbiased process!