Map reveals strange cosmos.

Op vrijdag 8 februari 2013 11:09:43 UTC+1 schreef Nicolaas Vroom het volgende:
Op donderdag 7 februari 2013 00:27:16 UTC+1 schreef Jos Bergervoet het volgende:

[Mod. note: correct. You will not get anything scientifically useful
by messing around with PNG files -- mjh]

PNG files are almost the same as BMP files. When you store and read those
files the accuracy stays the same. With JPG files that is not the case.
The biggest problem is to calculate the frequency (temperature)
from the color scheme.
With the fits file (a "text" file) I have the same problem.
The length of each record is 80 characters.
Each color is stored as alpha,red,green of blue.

Only a limited # of alpha values are possible (except 0):
all the values between 52 and 66. Highest is 62
all the values between 181 and 191. Highest is 189
For red all the values are possible
There is a small preference:
the values 0,1,2 and 3 have a very high chance.
Low chances are with 125,126 and 127.
128, 129 130 again have a very high chance
253, 254, 255 have again a low chance
For green and blue all the values have the same chance.
What this mean is that the accuracy IMO is not high.
(For the fits file tested) Of course I can be wrong.

Nicolaas Vroom

In article , Nicolaas Vroom
writes:

There are three things which happen around the same time:
combination (usually called recombination), matter becoming transparent
to radiation, and the energy density of radiation dropping below that of
matter. The three are related, but distinct processes. As you say, the
nomenclature can be confusing here.

The most confusing part is a clear description of the processes that
took place where and when. (with an indication how sure we are)

Sometimes, even people who should know better get it wrong and/or their
books suffer from typographical errors. Check out
http://www.jb.man.ac.uk/~jpl/cosmo/raine.html for example. Also, check
out http://www.jb.man.ac.uk/~jpl/cosmo/bad.html and in particular the
last item which probably more or less directly answers your questions in
this thread.

1) This document claims:
" Eventually, however, with the plasma at around 3000K, even these
photons become too feeble to prevent atoms forming.
With no free electrons left, photons have nothing to interact with and
travel freely through the Universe - they are said to have decoupled etc".
The question is what means freely? Does this imply undisturbed?

It means that they probably won't get re-absorbed.

2) My understanding of radiation (photons) is that they are created when
electrons move from a higher band to a lower band.

That's one way, but there are many others.

IMO what they should have added in #4 is:
How much from foreground, how much from intermediate (proto stars) and
how much from CMB.

These days, one observes the CMB at many different frequencies. The CMB
has the same structure at all frequencies (well, almost) whereas
foregrounds have different intensities at different frequencies, so
multi-frequency observations can help remove the foregrounds.

When you study page 14 of document in #4 above you will see that they use
the word intensity a lot. This indirectly IMO implies photon count.

Not in the sense in which this term is normally used in physics.

The document also shows that (only?) 5 frequency bands are measured
(K, Ka, Q, V and W) which indirectly implies that not all
CMB photons are not taken into account

One can extrapolate from the observed wave bands.

In article ,
Nicolaas Vroom writes:
1) This document claims:
" Eventually, however, with the plasma at around 3000K, even these
photons become too feeble to prevent atoms forming.
With no free electrons left, photons have nothing to interact with and
travel freely through the Universe - they are said to have decoupled etc".
The question is what means freely? Does this imply undisturbed?

Most CMB photons arrive undisturbed. Some are affected by hot gas in
galaxy clusters (Sunyaev-Zeldovich effect), others by interaction
with high-energy particles (inverse Compton effect), and a few others
simply absorbed by one thing or another (such as ionized gas in
galaxies). CMB measurements have to account for these effects.

2) My understanding of radiation (photons) is that they are created when
electrons move from a higher band to a lower band.

In general, electromagnetic radiation is emitted any time a charged
particle accelerates. See Maxwell's equations. For individual
photons, you have to use quantum mechanics, but the basic idea is the
same. The classical emission and absorption formula isn't wildly
wrong for astrophysical plasmas. (My memory is that it's off by a
factor of 5 or so for radio frequency of 1 GHz and typical
temperatures and densities.)

3) At page 287 of the Book "Astronomy and Cosmology" by Fred Hoyle 1975
below Figure 6.21 is written:
"Because of absorption and reemission and because of scattering inside
a (proto) star, radiation leaks out of the interior only very slowly"

Yes, that's when the protostar is neutral. Most of the absorption
comes from metals, not hydrogen or helium, but that's a detail.

At page 288 below Figure 6.22 is written:
When the temperature near the surface of a newly forming star falls below
4000 K the gases are no longer able to block the escape of radiation
in an effective way"

Yes, they become ionized. Notice that 4000 K is almost the same as
the 3000 K people talk about for the CMB. I haven't worked out the
numbers, but I expect the difference is because protostars are denser
than the CMB plasma.

4) From the document http://arxiv.org/abs/1212.5225 (9 Year Bennett)
At page 83 is written:
"5.3.7.3. ILC Considerations
The primary difficulty with any method of extracting the CMB from the data
is determining how much of the temperature in each pixel is foreground
and how much is CMB.
The data only constrain the sum of these two, and
we must make other assumptions in order to separate them.
The ILC specifically assumes that the CMB has a black body spectrum"

That's essentially what I wrote a few days ago. These facts are well
known.

IMO what they should have added in #4 is:
How much from foreground, how much from intermediate (proto stars) and
how much from CMB.

Protostars are part of the foreground. They aren't a very big part,
though, and they are confined to specific regions, mostly near the
Galactic plane.

When you study page 14 of document in #4 above you will see that they use
the word intensity a lot.

My guess is that they mean "specific intensity," though some people
shorten it. (The "specific" means per unit bandwidth of the
detector.) "Surface brightness" is another term. If you want to do
physical interpretations, you have to keep the units straight, but
that's not difficult.

This indirectly IMO implies photon count.

Any measurement in physical units implies photon count. The energy
of a photon is Planck's constant times its frequency, so converting
from energy units to photon units is trivial. The actual measurement
can come from any kind of detector.

The document also shows that (only?) 5 frequency bands are measured
(K, Ka, Q, V and W) which indirectly implies that not all
CMB photons are not taken into account

If the CMB were the only source in the sky, one frequency band would
suffice to measure it. More bands are used in order to separate the
foreground contributions, which have different temperatures, from the
desired CMB signal. For example, protostars have temperatures of a
few hundred kelvins and therefore will produce stronger signals at
higher frequencies.

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

Op donderdag 14 februari 2013 08:30:43 UTC+1 schreef Phillip Helbig---undress to reply het volgende:
In article , Nicolaas Vroom

IMO what they should have added in #4 is:
How much from foreground, how much from intermediate (proto stars) and
how much from CMB.

These days, one observes the CMB at many different frequencies. The CMB
has the same structure at all frequencies (well, almost) whereas
foregrounds have different intensities at different frequencies, so
multi-frequency observations can help remove the foregrounds.

When you study http://arxiv.org/pdf/1212.5225v2.pdf at page 45 you can see
that the planet Saturn generates photons which include the same
5 frequency bands which are characteristic for the CMB radiation.
All this noise has to be removed from the observed intensities.
The amount of noise per pixel can be "easily" estimated because Saturn
is a moving target.

When you study http://www.nasa.gov/mission_pages/hu...ience/xdf.html
you can see how much intermediate radiation there is
This image covers an area of approximate one pixel.
The problem is that the galaxies them self (like Saturn) also generate
a lot of CMB radiation. This noise has to be subtracted for all the visible
objects in this one pixel. To do that accurately I expect is very difficult.
Each galaxy in this image is surrounded by small black areas.
When you select a black spot inbetween two galaxies you can claim
that such a spot represents true CMB radiation which comes
from a source immediate behind that point at further distance.
However if you move towards the right (but still left of the galaxy)
this is not true anymore because also CMB radiated is bended.
That means that the source can come from behind the galaxy or
even from almost any place on the right.
When you move over the galaxy towards the right rim the reverse
starts to happen: The source of the CMB radiation can come
from almost any place towards the left.

For galaxies near us, this disturbance is more severe.

What I want to say because all stars at all distances generate
the same frequecies as CMB radiation it is very difficult
to establish which is which (which is real CMB)
Secondly, where the origin is of the CMB radiation. That means
the origin of the CMB radiation (a certain percentage) is
not the position of the pixel measured.

Nicolaas Vroom
http://users.pandora.be/nicvroom/

Op zaterdag 16 februari 2013 09:45:45 UTC+1 schreef Steve Willner het volgende:
In article ,

Nicolaas Vroom writes:
1) This document claims: etc

Most CMB photons arrive undisturbed. etc

This is part of the issue. The major issue is which percentage of
the photons in the 5 frequency bands have their origin very close after
the Big Bang. The problem is that (proto) stars also generate the
same type of photons.
The second issue is that all stars influence the path of the background
radiation. That means the true place of birth becomes obscure.


The document also shows that (only?) 5 frequency bands are measured
(K, Ka, Q, V and W) which indirectly implies that not all
CMB photons are not taken into account

If the CMB were the only source in the sky, one frequency band would
suffice to measure it. More bands are used in order to separate the
foreground contributions, which have different temperatures, from the
desired CMB signal. For example, protostars have temperatures of a
few hundred kelvins and therefore will produce stronger signals at
higher frequencies.

The issue is not temperatures but intensities at all frequencies
which all the intermediate stars (galaxies) produce within the
frequency range that is characteristic for the CMB radiation.
In reality this is not done: only a certain # of frequencies
are taken into account.
For the 5 frequencies considered the result is 5 corrected
intensities for each pixel (Healpix)
The second issue is calculate one result for each pixel.
This result could be the frequency of the maximum intensity
but I'am not sure.
The major issue is, as you seem to indicate, that it maybe is
impossible for certain pixels, to calculate any reliable intensity
for certain frequencies which represent CMB radiation.
The final issue is to give a physical interpretation for all
results calculated.

In summary the origin of the photons in the range from 23 to 94 Ghz
is partly from shortly after the Big Bang (500 million years) and
partly from (proto) stars born 1 billion years after the BB until
the present. The problem is how much is each.

Nicolaas Vroom
http://users.pandora.be/nicvroom/

On 2/18/13 8:47 AM, Nicolaas Vroom wrote:

In summary the origin of the photons in the range from 23 to 94 Ghz
is partly from shortly after the Big Bang (500 million years) and
partly from (proto) stars born 1 billion years after the BB until
the present. The problem is how much is each.


The peak frequency of Black Body radiation at 2.73 K is 160.4 GHz
Isn't it safe to assume that the CMB Black Body curve maintains itself
through 23 to 94 GHz
and can be used as a baseline for other component contribution?

Richard D. Saam

In article , "Richard D. Saam"
writes:

In summary the origin of the photons in the range from 23 to 94 Ghz
is partly from shortly after the Big Bang (500 million years) and
partly from (proto) stars born 1 billion years after the BB until
the present. The problem is how much is each.


The peak frequency of Black Body radiation at 2.73 K is 160.4 GHz
Isn't it safe to assume that the CMB Black Body curve maintains itself
through 23 to 94 GHz
and can be used as a baseline for other component contribution?

Of course, though historically one had to remove foreground sources in
order to observe this. Once it is established, then one can use this.
Other sources are not black bodies, hence observing in several frequency
bands allows one to remove foreground sources.

Note that almost all photons are CMB photons.

On 2/19/13 2:52 PM, Phillip Helbig---undress to reply wrote:
In article , "Richard D. Saam"
writes:


Note that almost all photons are CMB photons.

I would assume that this statement is true
in the context that there are
no theoretical lower or upper frequency limits
to the CMB Black Body Spectrum.
But there must be limits of some kind.

Op dinsdag 19 februari 2013 21:52:30 UTC+1 schreef Phillip Helbig---undress to reply het volgende:

Of course, though historically one had to remove foreground sources in
order to observe this.

One has to remove all contamination i.e. all photons in the
frequency band considered that are non CMB photons.

Figure 12 page 44 (http://arxiv.org/pdf/1212.5225v2.pdf 9 year) shows
what is partly involved. This part is relatif simple.
http://www.nasa.gov/mission_pages/hu...ience/xdf.html shows more.
This part is IMO extremly difficult because only one pixel
(out of many) is considered which contains many galaxies

An additional problem is gravitational lensing, that means the
bending of star light.

Document (http://arxiv.org/pdf/1212.5226v2.pdf 9 years) at page 23
in paragraph 5.3 explains that gravitational lensing can be used
to calculate cosmological parameters. (to our advantage)

The problem is that also CMB photons are bended. This works to our
disadvantage and makes a physical interpretation difficult.

Once it is established, then one can use this.
This is true in theory. In practice it is difficult to know for sure.

Other sources are not black bodies, hence observing in several frequency
bands allows one to remove foreground sources.

Note that almost all photons are CMB photons.
What do you mean ?
CMB photons originated shortly after the BB. Many are captured by intervening
stars which inturn also create photons at the same frequency.
I expect that from certain frequency bands for certain pixels maybe 90%
has to be removed, because of intermediate stars and proto stars.
See Figure 12 mentioned above.

Nicolaas Vroom
http://users.pandora.be/nicvroom/

In article , "Richard D. Saam"
writes:

Note that almost all photons are CMB photons.

I would assume that this statement is true
in the context that there are
no theoretical lower or upper frequency limits
to the CMB Black Body Spectrum.
But there must be limits of some kind.

Most photons in the universe are CMB photons. That is, they originate
there, and not in stars, planetary nebulae, disco lasers etc.

I don't see what limits have to do with this. Of course, at very high
and very low frequencies the intensity of the CMB (or any black body) is
low.