Telescopes combine to push frontier on galaxy clusters

March 11, 2016
Credit: X-ray: NASA/CXC/SAO/G.Ogrean et al.; Optical: NASA/STScI; Radio: NRAO/AUI/NSF

Galaxy clusters are enormous collections of hundreds or even thousands of galaxies and vast reservoirs of hot gas embedded in massive clouds of dark matter, invisible material that does not emit or absorb light but can be detected through its gravitational effects. These cosmic giants are not merely novelties of size or girth - rather they represent pathways to understanding how our entire universe evolved in the past and where it may be heading in the future.

To learn more about clusters, including how they grow via collisions, astronomers have used some of the world's most powerful telescopes, looking at different types of light. They have focused long observations with these telescopes on a half dozen . The name for this galaxy cluster project is the "Frontier Fields".

Two of these Frontier Fields galaxy clusters, MACS J0416.1-2403 (abbreviated MACS J0416) and MACS J0717.5+3745 (MACS J0717 for short) are featured here in a pair of multi-wavelength images.

Located about 4.3 billion light years from Earth, MACS J0416 is a pair of colliding galaxy clusters that will eventually combine to form an even bigger cluster. MACS J0717, one of the most complex and distorted galaxy clusters known, is the site of a collision between four clusters. It is located about 5.4 billion light years away from Earth.

These new images of MACS J0416 and MACS J0717 contain data from three different telescopes: NASA's Chandra X-ray Observatory (diffuse emission in blue), Hubble Space Telescope (red, green, and blue), and the NSF's Jansky Very Large Array (diffuse emission in pink). Where the X-ray and radio emission overlap the image appears purple. Astronomers also used data from the Giant Metrewave Radio Telescope in India in studying the properties of MACS J0416.

The Chandra data shows gas in the merging clusters with temperatures of millions of degrees. The optical data shows galaxies in the clusters and other, more distant, galaxies lying behind the clusters. Some of these background galaxies are highly distorted because of gravitational lensing, the bending of light by massive objects. This effect can also magnify the light from these objects, enabling astronomers to study background galaxies that would otherwise be too faint to detect. Finally, the structures in the radio data trace enormous shock waves and turbulence. The shocks are similar to sonic booms, generated by the mergers of the clusters.

New results from multi-wavelength studies of MACS J0416 and MACS J0717, described in two separate papers, are included below.

Credit: X-ray: NASA/CXC/SAO/G.Ogrean et al.; Optical: NASA/STScI; Radio: NRAO/AUI/NSF

An open question for astronomers about MACS J0416 has been: are we seeing a collision in these clusters that is about to happen or one that has already taken place? Until recently, scientists have been unable to distinguish between these two explanations. Now, the combined data from these various telescopes is providing new answers.

In MACS J0416 the (which leaves its gravitational imprint in the optical data) and the hot gas (detected by Chandra) line up well with each other. This suggests that the clusters have been caught before colliding. If the clusters were being observed after colliding the dark matter and hot gas should separate from each other, as seen in the famous colliding cluster system known as the Bullet Cluster.

The cluster in the upper left contains a compact core of hot gas, most easily seen in a specially processed image, and also shows evidence of a nearby cavity, or hole in the X-ray emitting gas. The presence of these structures also suggests that a major collision has not occurred recently, otherwise these features would likely have been disrupted. Finally, the lack of sharp structures in the radio image provides more evidence that a collision has not yet occurred.

In the cluster located in the lower right, the observers have noted a sharp change in density on the southern edge of the cluster. This change in density is most likely caused by a collision between this cluster and a less massive structure located further to the lower right.

Credit: X-ray: NASA/CXC/SAO/G.Ogrean et al.; Optical: NASA/STScI; Radio: NRAO/AUI/NSF

In Jansky Very Large Array images of this cluster, seven gravitationally-lensed sources are observed, all point sources or sources that are barely larger than points. This makes MACS J0717 the cluster with the highest number of known lensed radio sources. Two of these lensed sources are also detected in the Chandra image. The authors are only aware of two other lensed X-ray sources behind a galaxy .

All of the lensed radio sources are galaxies located between 7.8 and 10.4 billion light years away from Earth. The brightness of the galaxies at radio wavelengths shows that they contain stars forming at high rates. Without the amplification by lensing, some of these radio sources would be too faint to detect with typical radio observations. The two lensed X-ray sources detected in the Chandra images are likely active galactic nuclei (AGN) at the center of galaxies. AGN are compact, luminous sources powered by gas heated to millions of degrees as it falls toward supermassive black holes. These two X-ray sources would have been detected without lensing but would have been two or three times fainter.

The large arcs of radio emission in MACS J0717 are very different from those in MACS J0416 because of shock waves arising from the multiple collisions occurring in the former object. The X-ray emission in MACS J0717 has more clumps because there are four clusters violently colliding.

Georgiana Ogrean, who was at Harvard-Smithsonian Center for Astrophysics while leading the work on MACS J0416 research, is currently at Stanford University. The paper describing these results was published in the October 20th, 2015 issue of the Astrophysical Journal. The research on MACS J0717 was led by Reinout van Weeren from the Harvard-Smithsonian Center for Astrophysics, and was published in the February 1st, 2016 issue of the Astrophysical Journal.

Explore further: Dark matter and galaxies part ways in collision between hefty galaxy clusters

More information: Frontier Fields Clusters: Chandra and JVLA View of the Pre-Merging Cluster MACS J0416.1-2403. arxiv.org/abs/1505.05560

The discovery of lensed radio and X-ray sources behind the Frontier Fields cluster MACS J0717.5+3745 with the JVLA and Chandra. arxiv.org/abs/1512.04527

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19 comments

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Tuxford
1.6 / 5 (7) Mar 11, 2016
More merger mania gone wild looking for another patch.

In MACS J0416 the dark matter (which leaves its gravitational imprint in the optical data) and the hot gas (detected by Chandra) line up well with each other. This suggests that the clusters have been caught before colliding.


Yes, they line up well since the presence of the gas (matter) refracts light that the maniacs interpret as Invisible Magic Matter (IMM) in order to maintain their Huge Bang Fantasy model. This is the reason galaxies (such as ours) have IMM halos. See my comment:

http://phys.org/n...fty.html

So they provide only two possibilities, both involving collision. Instead, the galaxies are simply growing naturally from within as they are displaced from their origin near the center of the cluster. The center of the cluster will naturally be more dense with galaxies, as it is a simple matter of geometry. Think simple, not patch complex.
Old_C_Code
1 / 5 (8) Mar 11, 2016
B.S. Alert!!!

and vast reservoirs of hot gas embedded in massive clouds of dark matter, invisible material that does not emit or absorb light


Yawn. The mainstream science media ignorance of the state of matter known as PLASMA is staggering. Dark matter fudge has ruined astronomy. :(
Tektrix
5 / 5 (6) Mar 11, 2016
. . . ignorance of the state of matter known as PLASMA is staggering.


What's staggering is the persistence of ridiculous controversy.
Protoplasmix
5 / 5 (6) Mar 11, 2016
Phenomenal imagery. Looking forward to the day when you can get a roll of electronic wallpaper for the living room. I'd paper the ceiling too, total planetarium.
Phys1
5 / 5 (7) Mar 12, 2016
. . . ignorance of the state of matter known as PLASMA is staggering.


What's staggering is the persistence of ridiculous controversy.

It is not a controversy, it is one-sided idiocy.
NorseMythology
not rated yet Mar 12, 2016
Tektrix and phys1, what are you two talking about?
Captain Stumpy
5 / 5 (3) Mar 12, 2016
Tektrix and phys1, what are you two talking about?
@NorseMythology
the oft-debunked claims from the electric universe where they state that modern astrophysicists don't know anything about plasma physics, therefore we should all climb on the eu bandwagon because cantdrive, old-f, yep or hannes said so
and as leaders of the religion, only THEY can lead you to "truth" etc blah blah blah

they continue to regurgitate this false claim because:
... they believe repeating it adds legitimacy to it
(like any good religion or con which is also a pyramid scheme... in order for it to work, they need fresh meat so that they can build themselves up)

... and because they can't prove it (so like a religion, they simply repeat till someone falls for it)

... and because it's been debunked (so again, like a religion... you get the point, right?)
Phys1
5 / 5 (3) Mar 12, 2016
Tektrix and phys1, what are you two talking about?

Some posters here support pseudophysics of the Electrical Universe variety.
http://rationalwi...Universe
NorseMythology
4 / 5 (2) Mar 13, 2016
Thanks for the clarification. I hope you don't let the perhaps false conjecture of others taint your perception: the reality is, plasma and magnetism does play a dominant role in astrophysics.

Flux transfer events

Magnetohydrodynamics

Astrophysics fluid dynamics

Interstellar and intergalactic magnetic fields

For a good read on the role of plasma within our solar system Google

277-Ch21.pdf

Its a fascinating read, one I wish someone could render into a visual because it's challenging to imagine.
NorseMythology
5 / 5 (1) Mar 13, 2016
I should add, if you read the literature (the actual textbooks not trendy science website disseminations) it is clear astrophysicists are educated on and learned in regards to plasma.

I must confess, however, plasma does seem to be an avoided term. You read about space dust, gas, hot gas, ionized gas, dusty gas etc, in place of plasma. I don't understand this and it can be confusing and certainly looks suspicious especially to those who understand what those terms are referring to.
Phys1
not rated yet Mar 13, 2016
You read about space dust, gas, hot gas, ionized gas, dusty gas etc, in place of plasma.

Which one of these qualify as a a plasma?
Only the ionised gas, maybe.
See https://en.wikipe...finition
NorseMythology
not rated yet Mar 13, 2016
I have seen them all used in place of plasma.
Captain Stumpy
5 / 5 (2) Mar 13, 2016
the reality is, plasma and magnetism does play a dominant role in astrophysics
@NorseM
Absolutely! the problem isn't that they focus on plasma, it's that they make claims about it that can't be validated
to the eu cult, plasma is the answer regardless of the question, and gravity isn't even really considered (see their electric sun argument debunked here: http://www.tim-th...sun.html )
plasma does seem to be an avoided term
i think this has more to do with the scientific literacy problems of the targeted reader than anything else
if we consider the site is a clearing house for POP-Science articles and science news, you will have to actually consider the target audience, which is not so much the researcher as the general lay-public

IMHO - this is the reason they're no longer tied to moderated forums and they allow the comments to be flooded by pseudoscience - keep the numbers up
Captain Stumpy
5 / 5 (1) Mar 13, 2016
For a good read on the role of plasma within our solar system Google

277-Ch21.pdf

Its a fascinating read, one I wish someone could render into a visual because it's challenging to imagine.
@NorseM
thanks for the heads up...
if you like learning then here is a site you will like: http://ocw.mit.ed...ophysics

free! can't beat that, IMHO

there are a LOT of great courses there
NorseMythology
5 / 5 (2) Mar 13, 2016
Fantastic, thank you very much! It bothers me trying to read up on this topic and every journal wants me to pay to read, free is within my budget!
NorseMythology
1 / 5 (1) Mar 13, 2016
I'm glad you have noticed the term being... Avoided? IDK, I would like to think it is because it is pretty complex and not well understood yet, but they drone endlessly about dark matter and dark energy which are less understood (I am a layperson but I tend to side with Van Flandern on them being a fudge factor).

Who knows though, with much of the universe being gas and plasma, and the filamentary structure of the universe, the EU proponents May be onto something. I hope scientists don't shy away from it due to it's unfavorable stigma.

I just keep reading and keep an open mind, we don't have it figure doubt yet, I don't want to adhere to anything and blind myself to emerging understandings.
Captain Stumpy
5 / 5 (1) Mar 13, 2016
Fantastic, thank you very much! It bothers me trying to read up on this topic and every journal wants me to pay to read, free is within my budget!
@Norse
You are welcome. wish i could do more.
there are ways you can link studies privately on forums for perusal, just so you know - as long as the forum locks out BOT's as well as general public access (like with a password)

if you want to have access to a lot more, there are ways to get the papers you seek... some find it wrong, and some find it their only means to get the science. here is an article about it
http://www.scienc...pers-too

it requires the use of TOR
https://www.torproject.org/

not advocating for anything, just letting you know there are options for us very poor folk who can't fork out $ for every study they want
(sometimes patience pays off too... a LOT of studies eventually get out)
Captain Stumpy
5 / 5 (1) Mar 13, 2016
but they drone endlessly about dark matter and dark energy which are less understood
@Norse
well... those names are just placeholder names for something that is observed but not understood... so don't take the use of the names as being anything other than a substitute for saying "the unknown X that is observed but we don't fully understand yet"... it is just faster
Avoided?
yeah... but like i said, i think it has more to do with the target audience (which is usually younger and less scientifically literate)
I am a layperson
i wouldn't worry about that as long as you can link evidence or references supporting your claims (IOW- follow the scientific method) LOL
the EU proponents May be onto something
i never discount evidence... but where the eu fails is their lack of evidence and their failure to accept other evidence (discussed here: http://phys.org/n...tic.html )
that is the mark of religion, not science

Captain Stumpy
5 / 5 (1) Mar 13, 2016
I don't want to adhere to anything and blind myself to emerging understandings
@Norse
IOW- you follow the evidence .. right?
me too
nothing wrong with that
i always have an open mind... to the evidence

source matters with evidence (if they can't supply a reputable peer reviewed journal paper be skeptical - dont fall for it if it LOOKS legit, check it out)

important thing is to never assume that a web page is legit just because it exists (like the electric cosmos or thunderbolts sites)

just do research and think critically about the evidence, it's source, and it's validation (important in science - a singular study is a point of interest, IMHO, but it is validation that lends power to the paper)

levels of evidence are important: https://en.wikipe...evidence

always be skeptical and research it for yourself before accepting it as "fact"
and always authenticate and validate a claim

ENJOY
PEACE

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