A Space & astronomy forum. SpaceBanter.com

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » SpaceBanter.com forum » Astronomy and Astrophysics » Research
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

Galaxy cluster at z=4.31



 
 
Thread Tools Display Modes
  #1  
Old April 27th 18, 09:49 PM posted to sci.astro.research
jacobnavia
external usenet poster
 
Posts: 100
Default Galaxy cluster at z=4.31

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.

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?

If we look at that particular direction, do we see a change in the
composition of the CMB?

1.4 Gy after the big bang, that huge concentration of mass hasn't the
time to move a lot, and should be there as a variation of the CMB light.

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

What is more interesting, besides the death of the nth cosmology we have
produced, is that there is apparently an evolution or rather a change.
Galaxies were much younger 12.7 Gy ago. And this forming cluster, that
was already a heavyweight at that time, must be a gargantuan object now.

The team identified 14 galaies, and they are producing stars at an
incredible rate... the excesses of youth. :-)

But can we extrapolate from a few objects to an universal evolution?

Difficult. 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. This is a young object, but observer bias is a
reality: it is quite bright of course, given its huge dimensions and
star formation rates. Other objects, less luminous, could be there and
they could be old objects already then, 12.7 Gy ago.

In any case, this is not just a galaxy (as I have repeatedly reported in
this group) at this enormous distances that poses a huge problem. It is
a CLUSTER of them... with an incredible mass. Clusters weren't supposed
to exist before 10Gy ago. Now we find one at more than 12Gy!
Ads
  #2  
Old May 3rd 18, 09:37 PM posted to sci.astro.research
Steve Willner
external usenet poster
 
Posts: 1,142
Default Galaxy cluster at z=4.31

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.

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

  #3  
Old May 4th 18, 05:32 AM posted to sci.astro.research
jacobnavia
external usenet poster
 
Posts: 100
Default Galaxy cluster at z=4.31

Le 03/05/2018 à 22:37, Steve Willner a écrit :
Did you miss Fig 2 (right panel) in the paper? The mass is
consistent with model expectations.


Well, I detect that I look at what I want to see, I did miss the right
panel figure, because I read what it said about the LEFT panel:

quote
Most of the literature SMG overdensities are consistent with the model
expectations, whereas SPT2349-56 lies vastly above the region spanned by
the model.
end quote

So the models do not fit at all for the left panel.

You point correctly that the right panel shows that the models could
account for the same object!

I did not read that. Observer bias from my side :-)

Anyway, the question remains:

how can you make a cluster of this mass in only 1.2Gy?

And yes, many detected objects are young and bright in the far away
universe, but since those objects are bright there could be an observer
bias in our observations!

Older and far less luminous objects could be abundant but beyond the
powers of ALMA.

You did not quote that part of my message...

What is interesting is that there could be an evolution in the universe,
and maybe the galaxy formation process started somewhere sometime in a
huge undifferentiated gas cloud. Not a "big bang" but a beginning of an
ongoing condensation process in our local cloud.

With an ALMA version 2.0 maybe it will be possible to find out lensed
galaxies in that cluster, and if we find them, we could start answering
those questions. In any case, finding such a lensed galaxy in this
cluster would definitely disprove any big bang.

Thanks for your input.

  #4  
Old May 11th 18, 09:44 AM posted to sci.astro.research
Steve Willner
external usenet poster
 
Posts: 1,142
Default Galaxy cluster at z=4.31

The paper in question is now published at
http://www.nature.com/articles/s41586-018-0025-2
but you will need to pay or have a subscription.

I am reluctant to respond further, but there seems to be one point of
confusion I can clear up:

In article ,
jacobnavia writes:
how can you make a cluster of this mass in only 1.2Gy?


As noted, the models do so, as shown in Fig 2 (right panel).

So the models do not fit at all for the left panel.


Which shows something related to linear size. As was stated in the
paper, the models for cluster size omit galaxy interactions, which
will (it seems) make real clusters smaller than the models say.

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




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
WBL 524 Galaxy Cluster WA0CKY Astro Pictures 0 December 15th 14 09:07 AM
ASTRO: Pegasus I Galaxy Cluster Rick Johnson[_2_] Astro Pictures 1 March 17th 14 10:32 PM
Galaxy cluster at z=1.4 challenges BBT Max Keon Astronomy Misc 21 July 27th 05 12:37 PM
Galaxy cluster at z=1.4 challenges BBT [email protected] Research 119 June 7th 05 10:22 AM
Galaxy cluster at z=1.4 challenges BBT Max Keon Astronomy Misc 1 June 6th 05 12:48 PM


All times are GMT +1. The time now is 06:35 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
Copyright ©2004-2018 SpaceBanter.com.
The comments are property of their posters.