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Beyond IDCS J1426.5+3508



 
 
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  #21  
Old July 1st 12, 06:34 PM posted to sci.astro.research
Phillip Helbig---undress to reply
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Default Beyond IDCS J1426.5+3508

In article , Eric Flesch
writes:

On Sun, 01 Jul 12, Phillip Helbig wrote:
How probable is it that the Moon and the Sun have the same angular size?


Possibly close to 1, due to the anthropic principle: such a moon may
have been needed to give the Earth tectonic and rotational stability
across epochs, else we wouldn't have evolved to be discussing it.


Isaac Asimov pointed out in an essay called "The Triumph of the Moon"
(collected in the book THE TRAGEDY OF THE MOON, which contains an essay
by the same name) that the fact that the Moon is large in relation to
the Earth (compared to the ratios for other planets and moons) might
have an anthropic explanation. However, this cannot explain the nearly
perfect coincidence in size. (Also consider that, since the Moon is
moving away from the Earth, the coincidence holds only for a relatively
short time during the history of the Earth.)
  #22  
Old July 2nd 12, 08:03 PM posted to sci.astro.research
Phillip Helbig---undress to reply
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Default Beyond IDCS J1426.5+3508

In article , Phillip
Helbig---undress to reply writes:

One needs to interpret such rare objects properly. See recent work by
Ian Harrison and Peter Coles on extreme-value statistics in cosmology:

http://telescoper.wordpress.com/2011...-the-universe/


Note that Peter Coles criticizes the Gonzalez et al. paper on other
grounds:

http://telescoper.wordpress.com/2012...d-peer-review/
  #23  
Old July 7th 12, 07:21 AM posted to sci.astro.research
Steve Willner
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Default Beyond IDCS J1426.5+3508

In article ,
Jos Bergervoet writes:
OK, in Fig. 1 there, 4 to 5E14 Msun at this redshift seems to
be right at the expected largest mass seen. Excellent fit!


The paper in question (Harrison and Coles 2012 MNRAS 421, L19) can be
located via
http://adsabs.harvard.edu/abs/2012MNRAS.421L..19H

The worry is that the curve is for the whole sky, while our surveys
have so far covered only a small fraction of the sky. We might just
have been lucky, but maybe there's something we don't have quite
right just yet.

Of course tweaking some parameters or attributing unexpected
properties to dark matter is a very long way from throwing out the
whole Big Bang/lambda-CDM model. And even minor tweaking on this
basis is premature at the moment.

There is a real problem, however, with the 775 nm magnitude of the
lensed source. Even with lensing, it's too bright for the population
of known z3 objects.


Do we also have statistical expectation curves for this? Like
the one above, but for any luminous object at this higher z,
and then combined with the probability of it being lensed?
A somewhat complicated combination of probability distributions
seems to be needed here, apparently shown in Fig. 3 in the
preprint: http://arxiv.org/abs/1205.3788


As you say, Fig 3 tells the story. The calculation is complicated
because it has to take into account all possible redshifts 1.75 and
all possible alignments between the lensing cluster and the
background galaxy. The alignment affects the magnification, which
means one is looking for a different intrinsic magnitude at each
possible alignment and redshift. There is additional uncertainty
because the lens mass distribution is poorly known.

What Fig 3 says, though, is that _based on known populations_ of
z 1.75 objects, the observed 775 nm magnitude of the lensed object
is wildly improbable. Either the authors' calculation is wrong (and
I haven't checked it) or based on incorrect data, or there is a
hitherto unknown population of high-z galaxies, or something is wrong
with the cosmology. I wouldn't bet very much on the third of these.
(And maybe there are other possibilities I'm missing.) As I wrote
earlier, it will be interesting to see how this plays out.

The figure seems to show quite some uncertainty (the two curves
plotted are quite different)


The curves are for two different wavelengths, 1600 and 775 nm. (The
notation is somewhat obscure; it refers to HST filters.) The 1600 nm
magnitude is a bit surprising but within range of reasonable
uncertainties. The 775 nm magnitude is way out of range.

--
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Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
  #24  
Old August 15th 12, 03:12 AM posted to sci.astro.research
jacob navia[_5_]
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Default Beyond IDCS J1426.5+3508

Le 26/06/12 22:11, jacob navia a ecrit :
[snip]

That cluster could be "explained away".

Tomorrow there is an announcement by NASA that seems to have discovered
a new one, even further away!


Interesting times...
  #25  
Old August 16th 12, 05:17 AM posted to sci.astro.research
Eric Gisse
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Default Beyond IDCS J1426.5+3508

On Aug 14, 9:12*pm, jacob navia wrote:
Le 26/06/12 22:11, jacob navia a ecrit :
[snip]

That cluster could be "explained away".

Tomorrow there is an announcement by NASA that seems to have discovered
a new one, even further away!

Interesting times...


Just consider the following question every time you see something
really far away, but prior to being so surprised:

"At what point should the universe have developed?"

Have an open mind.
  #26  
Old August 16th 12, 11:04 AM posted to sci.astro.research
jacob navia[_5_]
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Default Beyond IDCS J1426.5+3508

Le 15/08/12 04:12, jacob navia a écrit :
Le 26/06/12 22:11, jacob navia a ecrit :
[snip]

That cluster could be "explained away".

Tomorrow there is an announcement by NASA that seems to have discovered
a new one, even further away!


Interesting times...


False alarm,sorry. That announcement was about the Phoenix cluster,
"just" 5 Billion years away.
  #27  
Old August 16th 12, 11:05 AM posted to sci.astro.research
jacob navia[_5_]
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Default Beyond IDCS J1426.5+3508

Le 16/08/12 06:17, Eric Gisse a écrit :
On Aug 14, 9:12 pm, jacob navia wrote:
Le 26/06/12 22:11, jacob navia a ecrit :
[snip]

That cluster could be "explained away".

Tomorrow there is an announcement by NASA that seems to have discovered
a new one, even further away!

Interesting times...


Just consider the following question every time you see something
really far away, but prior to being so surprised:

"At what point should the universe have developed?"

Have an open mind.


I do not understand your point.

What does it mean "At what point should the universe have developed"
makes no sense to me.

Personally I doubt that a half animal species, that has never went
beyond the cradle of his little planet can say something about
"the universe".

We have always had a "theory of the universe" since we left the caves
we used to live in.

And it was always wrong, as we learned when we observed a little bit
more of it.

This time is no different.

But in any case the announcement of NASA didn't concern cosmology but
astronomy, two separate fields.

The Phoenix cluster looks special, its central black hole can't keep
matter falling into its center and is building stars at a prodigious
rate.

So, I was jumping to conclusions, something I should avoid because
I do want to keep an open mind.
  #28  
Old September 10th 12, 04:31 PM posted to sci.astro.research
Richard D. Saam
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Default Beyond IDCS J1426.5+3508

On 7/1/12 3:00 AM, Phillip Helbig---undress to reply wrote:
In article , "Richard D. Saam"
writes:

How about framing the question in terms of a more defined
Supernovae Type 1a standard candle condition.

Use the distance modulus equation:

m-M = 5 log(d) - 5

then d = 10^((m-M)/5 - 1)

From Supernovae compilation
http://supernova.lbl.gov/Union/figur....1_mu_vs_z.txt

the current maximum Type 1A redshift
2003dy z = 1.34 m-M = 45.0675055813

d = 10^((m-M)/5 - 1) = 1.03E+08 parsec or 3.18E+26 cm


I haven't checked the actual numbers, but OK so far.

This is about 2.5 percent of the present universe


First, note that the distance involved is the luminosity distance.
There is little point in expressing this in terms of the

radius


of the universe.

luminosity distance is a distance measured by luminosity but a distance
is a distance and a function of z.
It is understood that universe radius is subject to the particular model
used and can be expressed as a function of z
A model can be used wherein the Hubble sphere expands at c

assuming expansion from the Big Bang
at the speed of light c/H = 1.30E+28 cm


Not sure what you mean here. The speed of light is not a limiting
factor for the expansion of the universe.


The speed of light is not in the general view a limiting factor for the
expansion of the universe
but this view does not negate the possibility that it is.

If z=1.34, then the universe is 2.34 times larger now than when the
light was emitted. This is independent of the cosmological model.

In the limited view, one could consider that 2.34 larger based on speed
of light

So why does type 1A 2003dy standard candle redshift (z=1.34)
represent a condition within ~2.5% of the Big Bang
with its z in the thousands and probably much greater?


I do not understand this. What does the "z in the thousands" mean?


"z in the thousands" in the context that the first light was at z~1000

  #29  
Old September 11th 12, 01:18 AM posted to sci.astro.research
Phillip Helbig---undress to reply
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Posts: 629
Default Beyond IDCS J1426.5+3508

In article , "Richard D. Saam"
writes:

From Supernovae compilation
http://supernova.lbl.gov/Union/figur....1_mu_vs_z.txt

the current maximum Type 1A redshift
2003dy z = 1.34 m-M = 45.0675055813

d = 10^((m-M)/5 - 1) = 1.03E+08 parsec or 3.18E+26 cm


I haven't checked the actual numbers, but OK so far.

This is about 2.5 percent of the present universe


First, note that the distance involved is the luminosity distance.
There is little point in expressing this in terms of the

radius


of the universe.

luminosity distance is a distance measured by luminosity but a distance
is a distance and a function of z.


Right. However, what does it mean that it is 2.5 percent of the present
universe? What is the luminosity distance to z=infinity? (Hint: much
larger than the speed of light times the age of the universe.) Yes, one
can express it as a percentage, but the question is whether this is
useful.

It is understood that universe radius is subject to the particular model
used and can be expressed as a function of z


OK.

A model can be used wherein the Hubble sphere expands at c


Yes, although this doesn't correspond to our universe.

So why does type 1A 2003dy standard candle redshift (z=1.34)
represent a condition within ~2.5% of the Big Bang
with its z in the thousands and probably much greater?


Because you are confusing different types of distance and because
distance is a non-linear function of redshift.
  #30  
Old September 11th 12, 08:05 AM posted to sci.astro.research
Richard D. Saam
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Default Beyond IDCS J1426.5+3508

On 9/10/12 7:18 PM, Phillip Helbig---undress to reply wrote:
Right. However, what does it mean that it is 2.5 percent of the present
universe? What is the luminosity distance to z=infinity? (Hint: much
larger than the speed of light times the age of the universe.) Yes, one
can express it as a percentage, but the question is whether this is
useful.


Yes in the conventional view, luminosity distance to z=infinity is much
larger than speed of light times the age of the universe.
This points to an error in concept.
What is a non linear distance function of redshift
such that distance approaches
speed of light times the age of the universe
as redshift approaches infinity?

[Mod. note: quoted text trimmed -- mjh]
 




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