Witnessing a Galactic Pileup:

[beecee]

https://phys.org/news/2018-04-astronomers-witness-galaxy-megamerger.html

Peering deep into space—an astounding 90 percent of the way across the observable universe—astronomers have witnessed the beginnings of a gargantuan cosmic pileup, the impending collision of 14 young, starbursting galaxies.

This ancient megamerger is destined to evolve into one of the most massive structures in the known universe: a cluster of galaxies, gravitationally bound by dark matter and swimming in a sea of hot, ionized gas.


Read more at: https://phys.org/news/2018-04-astronomers-witness-galaxy-megamerger.html#jCp

The results are published in the journal Nature.

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the paper:

https://www.nature.com/articles/s41586-018-0025-2

A massive core for a cluster of galaxies at a redshift of 4.3:

 

Abstract

Massive galaxy clusters have been found that date to times as early as three billion years after the Big Bang, containing stars that formed at even earlier epochs1,2,3. The high-redshift progenitors of these galaxy clusters—termed ‘protoclusters’—can be identified in cosmological simulations that have the highest overdensities (greater-than-average densities) of dark matter4,5,6. Protoclusters are expected to contain extremely massive galaxies that can be observed as luminous starbursts7. However, recent detections of possible protoclusters hosting such starbursts8,9,10,11 do not support the kind of rapid cluster-core formation expected from simulations12: the structures observed contain only a handful of starbursting galaxies spread throughout a broad region, with poor evidence for eventual collapse into a protocluster. Here we report observations of carbon monoxide and ionized carbon emission from the source SPT2349-56. We find that this source consists of at least 14 gas-rich galaxies, all lying at redshifts of 4.31. We demonstrate that each of these galaxies is forming stars between 50 and 1,000 times more quickly than our own Milky Way, and that all are located within a projected region that is only around 130 kiloparsecs in diameter. This galaxy surface density is more than ten times the average blank-field value (integrated over all redshifts), and more than 1,000 times the average field volume density. The velocity dispersion (approximately 410 kilometres per second) of these galaxies and the enormous gas and star-formation densities suggest that this system represents the core of a cluster of galaxies that was already at an advanced stage of formation when the Universe was only 1.4 billion years old. A comparison with other known protoclusters at high redshifts shows that SPT2349-56 could be building one of the most massive structures in the Universe today.

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Three questions arising from this article and paper. I have highlighted the relevant sentences.

[1] Is this further evidence for DM?

[2]Forming stars up to a 1000 times faster than our own galaxy....because of the abundance of accreting hydrogen [and helium] gas I presume?

[3] Re all these starburst galaxies lying at 4.31 redshift....I'm pretty sure we have observed galaxies at far greater redshifts...up to 7, 8 and 9 in fact. Awesome cosmological science sure, but  other then the observation of a galactic pileup, what is the real significance of this? [I'm probably missing something]

Edited April 25, 2018 by beecee

[Mordred]

Nice find thanks for sharing, will read up further on it then get back to your questions

Edited April 25, 2018 by Mordred

[Mordred]

6 hours ago, beecee said:

 

[1] Is this further evidence for DM?

 

Definetely further evidence for DM but also stronger support its involvement in superstructure formation. 

6 hours ago, beecee said:

 

[2]Forming stars up to a 1000 times faster than our own galaxy....because of the abundance of accreting hydrogen [and helium] gas I presume?

 

  correct 

6 hours ago, beecee said:

 

[3] Re all these starburst galaxies lying at 4.31 redshift....I'm pretty sure we have observed galaxies at far greater redshifts...up to 7, 8 and 9 in fact. Awesome cosmological science sure, but  other then the observation of a galactic pileup, what is the real significance of this? [I'm probably missing something]

 

Yes we have however the significants is the scale of this overdensity.

I am currently reading reference 1 here is the arxiv. Lots of detail here. Side note [latex]M_{200c}[/latex] if I recall correctly is 200 times critical density.

https://arxiv.org/abs/1604.07404

Edited April 26, 2018 by Mordred

[beecee]

5 hours ago, Mordred said:

Definetely further evidence for DM but also stronger support its involvement in superstructure formation. 

  correct 

 

Yes we have however the significants is the scale of this overdensity.

I am currently reading reference 1 here is the arxiv. Lots of detail here. Side note M200c if I recall correctly is 200 times critical density.

https://arxiv.org/abs/1604.07404

Vinaka Mordred, much appreciated.