Number of Galaxies Underestimated by 90%

Dear Yousuf Khan:

On Mar 25, 8:09*am, Yousuf Khan wrote:
Sam Wormley wrote:
On 3/25/10 8:56 AM, Yousuf Khan wrote:
This might have implications for Dark Matter &
Dark Energy estimates. If the ratio of galaxies
is 9 times higher than observed, then that
completely removes the need for Dark Matter to
explain anything.

* Wrong. The distribution of matter would NOT
account for the galactic rotation speeds observed!

No, but the modified gravity theories would.

Only f( R ) survived. TeVeS received a fatal blow.

Modified gravity, plus an underestimation of the
number of galaxies in clusters removes all need
for Dark Matter. Get it?

There are still "filaments" of Dark Matter between visible galaxies...
I think you are being a little hasty yet...

David A. Smith

dlzc wrote:
Dear Yousuf Khan:

On Mar 25, 8:07 am, Yousuf Khan wrote:
JohnF wrote:
How would it (more normal baryonic matter) explain
accelerating expansion?
It wouldn't, but it would explain Dark Matter.

No, it wouldn't explain Dark Matter. Dark Matter is found also within
galaxies. Now we have mapped DM between galaxies, perhaps some of
that is just normal matter that is not yet detectable at the energy
levels we can "see" with.

David A. Smith

Replace the galaxy rotation curves with modified gravity, and all need
for Dark Matter disappears.

Yousuf Khan

dlzc wrote:
Dear Yousuf Khan:

On Mar 25, 8:09 am, Yousuf Khan wrote:
Sam Wormley wrote:
Wrong. The distribution of matter would NOT
account for the galactic rotation speeds observed!
No, but the modified gravity theories would.

Only f( R ) survived. TeVeS received a fatal blow.

Actually, neither of them would be necessary after this. You can go
right back to first principals, and resurrect the grand-daddy of
modified gravity, MOND. MOND + GR/Cosmological Constant would be
sufficient to explain the galactic scale all of the way upto the cosmic
scale.

Modified gravity, plus an underestimation of the
number of galaxies in clusters removes all need
for Dark Matter. Get it?

There are still "filaments" of Dark Matter between visible galaxies...
I think you are being a little hasty yet...


The filaments are most likely also explainable by unseen galaxies.

Plus that other article I just posted about the lack of runaway
supermassive blackhole expansion puts an upper limit on the density of
Dark Matter to a level that makes it impossible to be the source of
those "filaments".

Yousuf Khan

Yousuf Khan wrote:
http://www.shortnews.com/start.cfm?id=83500

Here's a more detailed article about this discovery.

Cosmos has billions more stars than thought - Yahoo! News
"The astronomers carried out two sets of observations in the same
region, hunting for light emitted by galaxies born 10 billion years ago.

The first looked for so-called Lyman-alpha light, the classic telltale
used to compile cosmic maps, named after its US discoverer, Theodore
Lyman. Lyman-alpha is energy released by excited hydrogen atoms.

The second observation used a special camera called HAWK-1 to look for a
signature emitted at a different wavelength, also by glowing hydrogen,
which is known as the hydrogen-alpha (or H-alpha) line.

The second sweep yielded a whole bagful of light sources that had not
been spotted using the Lyman-alpha technique."
http://news.yahoo.com/s/afp/20100324...c2hhc2 JpbA--

In article ,
Yousuf Khan writes:
This might have implications for Dark Matter & Dark Energy
estimates.

Hardly!

The paper is by Hayes, Schaerer, and Ostlin (2010 A&A 509, L5; also
http://arxiv.org/abs/0912.3267). They have measured the H-alpha
luminosity function at z=2.2. H-alpha is a measure of star formation
rate (SFR), not stellar mass, and the answer the new paper gets for
SFR is squarely in the middle of existing data. (See Fig 3 of the
paper.) I am not sure where "underestimated by 90%" comes from, but
it seems to be something to do with Lyman-alpha estimates before
correction for extinction. Measuring H-alpha greatly decreases the
extinction correction, but the actual result is that the earlier
estimates were pretty much correct.

It doesn't pay to take a "headline number" too seriously unless you
know exactly what's been measured and how.

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA

dlzc wrote:
As to this current thread, now I see us with having *too much* normal
matter. Big Bang cosmology only needed "67%" (some large but not
impossible amount, might be close to this) more normal matter, which
was determined to be surprising amounts of intergalactic hydrogen and
oxygen spotted between us and quasars.

David A. Smith

What exactly are you referring to by the "67%"? Big Bang needed 67% of
what?

Yousuf Khan

Steve Willner wrote:
Hardly!

The paper is by Hayes, Schaerer, and Ostlin (2010 A&A 509, L5; also
http://arxiv.org/abs/0912.3267). They have measured the H-alpha
luminosity function at z=2.2. H-alpha is a measure of star formation
rate (SFR), not stellar mass, and the answer the new paper gets for
SFR is squarely in the middle of existing data. (See Fig 3 of the
paper.) I am not sure where "underestimated by 90%" comes from, but
it seems to be something to do with Lyman-alpha estimates before
correction for extinction. Measuring H-alpha greatly decreases the
extinction correction, but the actual result is that the earlier
estimates were pretty much correct.

It doesn't pay to take a "headline number" too seriously unless you
know exactly what's been measured and how.


Although H-alpha might typically be used for star-formation rates, they
used it in this case to count galaxy locations. What they found was that
there were more sources of H-alpha than there were sources of
Lyman-alpha. That means that star formation was happening in places
where we can't see a galaxy, but since star formation was happening
there, then a galaxy must exist there. So the H-alpha won't be able to
tell us the mass of that invisible galaxy, but it will mark its location.

Yousuf Khan

Dear Yousuf Khan:

On Mar 25, 12:37*pm, Yousuf Khan wrote:
dlzc wrote:
As to this current thread, now I see us with having
*too much* normal matter. *Big Bang cosmology
only needed "67%" (some large but not impossible
amount, might be close to this) more normal matter,
which was determined to be surprising amounts of
intergalactic hydrogen and oxygen spotted between
us and quasars.

What exactly are you referring to by the "67%"? Big
Bang needed 67% of what?

"Missing normal matter". Now we appear to have *way* too much normal
matter, to allow this Universe to form...
http://www.colorado.edu/news/r/81c6b...24a37bdd6.html

David A. Smith

Yousuf Khan wrote:

This might have implications for Dark Matter & Dark Energy estimates. If
the ratio of galaxies is 9 times higher than observed, then that
completely removes the need for Dark Matter to explain anything.

Other than dynamical systems which still display dark matter.

Most this will do is tweak the global baryon density by a few points upward.


Yousuf Khan

***
Number of Galaxies Underestimated by 90%
"According to Europe´s Very Large Telescope located in Chile, an
uncovering of previously unseen galaxies has occurred.

Some parts of the universe may have been underestimated by up to 90%.
According to the leading investigator, it means that for every 10
galaxies located, 100 were not being observed.

That there's a selection bias in play is surprising to nobody. Or should be.


Interstellar clouds and space dust may have blocked light from reaching
Earth. HAWK-1, a special camera able to observe signature emissions at a
specific wavelength, unveiled clusters of previously unseen galaxies."
http://www.shortnews.com/start.cfm?id=83500

eric gisse wrote:
Yousuf Khan wrote:

This might have implications for Dark Matter & Dark Energy estimates. If
the ratio of galaxies is 9 times higher than observed, then that
completely removes the need for Dark Matter to explain anything.

Other than dynamical systems which still display dark matter.

You're talking about galaxy rotation curves? That's always been the
domain where modified gravity theories have had much higher success than
Dark Matter theories.

Most this will do is tweak the global baryon density by a few points upward.

Up until now, we've been told that Dark Matter outweighs galaxies 5:1.
So if there are now 9 times as many galaxies as previously thought, we
no longer need to consider Dark Matter anymore, because it's no longer
Dark Matter, it was simply missing galaxies. Dark Matter therefore
didn't turn out to be WIMPs, MACHOs, Axions, sterile neutrinos, or any
of the other theories about what Dark Matter could be.

Some parts of the universe may have been underestimated by up to 90%.
According to the leading investigator, it means that for every 10
galaxies located, 100 were not being observed.

That there's a selection bias in play is surprising to nobody. Or should be.

Oh, come one! Everybody knew there were some unseen galaxies, but nobody
ever expected it to be 9 times as many as seen galaxies.


Yousuf Khan