APOD: The Fornax Cluster of Galaxies (2022 Jan 29)

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APOD: The Fornax Cluster of Galaxies (2022 Jan 29)

Post by APOD Robot » Sat Jan 29, 2022 5:05 am

Image The Fornax Cluster of Galaxies

Explanation: Named for the southern constellation toward which most of its galaxies can be found, the Fornax Cluster is one of the closest clusters of galaxies. About 62 million light-years away, it is almost 20 times more distant than our neighboring Andromeda Galaxy, and only about 10 percent farther than the better known and more populated Virgo Galaxy Cluster. Seen across this two degree wide field-of-view, almost every yellowish splotch on the image is an elliptical galaxy in the Fornax cluster. Elliptical galaxies NGC 1399 and NGC 1404 are the dominant, bright cluster members toward the upper left (but not the spiky foreground stars). A standout barred spiral galaxy NGC 1365 is visible on the lower right as a prominent Fornax cluster member.

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Re: APOD: The Fornax Cluster of Galaxies (2022 Jan 29)

Post by VictorBorun » Sat Jan 29, 2022 9:36 am

I wonder if the Fornax Cluster is real dense with galaxies or is just a disk cluster seen edge-on?
Why a pic of Andromeda and Triangulum shows them tiny and far apart?

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Re: APOD: The Fornax Cluster of Galaxies (2022 Jan 29)

Post by Ann » Sat Jan 29, 2022 12:29 pm

APOD January 29 2022 Fornax Cluster Lorenzi annotated.png

Two things stand out in the Fornax Cluster of galaxies (henceforth: the Fornax Cluster). The most striking object in the cluster is obviously the fantastic large barred grand design (two-armed) spiral NGC 1365 at lower right. The other striking aspect of the image is that virtually all the other galaxies in the image (except tiny NGC 1427A at far left) are "all yellow" and therefore (almost) completely lacking in star formation. We may also note that the largest yellow galaxy in the cluster, NGC 1399, completely lacks any structures or visible features. NGC 1399 is a perfect example of a giant elliptical galaxy.

hs-article-0720a-2400x1840[1].jpg
Giant galaxy cluster Abell 370.NASA, ESA, and J. Lotz and the HFF Team

It is interesting to compare the Fornax Cluster with the giant distant galaxy cluster Abell 370. A striking similarity is that so many of the galaxies are yellow, that the largest galaxies are ellipticals, and that so few of the galaxies show any obvious structures of features.

A striking difference between Abell 370 and the Fornax Cluster is the presence of all the streaks and arcs in Abell 370. These are background galaxies whose light is being magnified and whose (apparent) shapes are being stretched by the strongly curved spacetime caused by the tremendous mass of Abell 370. (Speaking of which - Abell 370 is a supergiant galaxy cluster crammed full of member galaxies, which the Fornax Cluster clearly is not!)

An interesting similarity between the Fornax Cluster and Abell 370 is that the bluest starforming galaxies (of those that are likely to be at the same distance from us as the cluster) are located at the outskirts of the cluster. The same pattern can be seen in the Coma Cluster. Yellow elliptical galaxies NGC 4889 and NGC 4874 are at the center of the cluster, and spiral galaxies NGC 4911 and NGC 4921 that contain some star formation (although not a lot) are at the outskirts of the cluster.


An oddball among galaxy clusters is the Hercules Cluster of galaxies, which contains many spirals and blue starforming galaxies even in its central part. The way I understand it, the Hercules Cluster is believed to be a galaxy cluster that formed recently when two smaller clusters collided or merged. In other words, the Hercules Cluster is not old enough to have evolved into a typical galaxy cluster whose members are mostly "red and dead" ellipticals and lenticulars (galaxies with disks but no spiral arms) and which contains a massive elliptical galaxy in its center.

Why does star formation stop in so many galaxies in galactic clusters? A probable reason is that all the galactic interactions in the dense cluster environment cause galaxies to expend their available gas reservoirs prematurely:


Galactic jostling in dense environments, and triggered bursts of violent star formation, are likely to deplete galaxies in clusters of much of their star forming raw material. Another gas-thief is ram pressure:


NGC 1427A, which can be seen at far left in today's APOD, is falling through the hot intergalactic medium of the Fornax Cluster, and it is being strongly affected by ram pressure. This causes NGC 1427A to form a lot of stars and at the same time lose a lot of its gas.

One reason why galaxies in dense galaxy clusters lose their star forming ability may be that the dominant elliptical galaxy of such clusters typically pump energy into the entire cluster through the jets emitted by the accretion disks of their black holes. This continuous injection of energy into the entire intergalactic medium surrounding the dominant galaxy affects the neighboring galaxies too and prevents their own gas from cooling down enough to form stars.


The above image gives you an idea of the power of the jets emitted by the accretions disks of supergiant elliptical galaxies and the effects they may have on their environments.

Ann
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Re: APOD: The Fornax Cluster of Galaxies (2022 Jan 29)

Post by orin stepanek » Sat Jan 29, 2022 1:25 pm

FornaxC1_FB1024.jpg
Galaxies galore! NGC 1365 is an eye catcher as it is very prominent
on the photo; but it is a beauty! 8-)
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Re: APOD: The Fornax Cluster of Galaxies (2022 Jan 29)

Post by NCTom » Sat Jan 29, 2022 2:46 pm

Would the Fornax Cluster include the most distant galaxies visible in this photo, or are those so distant as to be included only because they are located in that direction? Is it possible to determine the true size of this cluster (any cluster) and its number of members?

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Re: APOD: The Fornax Cluster of Galaxies (2022 Jan 29)

Post by Chris Peterson » Sat Jan 29, 2022 2:51 pm

NCTom wrote: Sat Jan 29, 2022 2:46 pm Would the Fornax Cluster include the most distant galaxies visible in this photo, or are those so distant as to be included only because they are located in that direction? Is it possible to determine the true size of this cluster (any cluster) and its number of members?
If they're really distant and not just small, than no, they are probably not part of the cluster. Cluster members can be identified by redshift - all will have similar values (really, the same value of cosmological redshift, with a slight increase or decrease caused by Doppler shift). I think the number of members and the approximate total mass is pretty well known.

The cluster is defined by the galaxies that are gravitationally bound, not by the common field they lie in.
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Re: APOD: The Fornax Cluster of Galaxies (2022 Jan 29)

Post by Ann » Sat Jan 29, 2022 4:22 pm

NCTom wrote: Sat Jan 29, 2022 2:46 pm Would the Fornax Cluster include the most distant galaxies visible in this photo, or are those so distant as to be included only because they are located in that direction? Is it possible to determine the true size of this cluster (any cluster) and its number of members?
You may read about the Fornax Cluster here. This Wikipedia page tells you about the distance to this cluster, and it lists many of its members. Wikipedia also says that the Fornax Cluster is considerably smaller than the Virgo cluster.

I haven't been able to spot any obvious background clusters in the same part of the sky as the Fornax Cluster. But I'd like to show you what a background cluster might look like.

Tadpole galaxy with background group.png

Note that the background galaxies at upper left are all small and highly reddened. They are also close together, which is why I believe that they are gravitationally bound. They would therefore constitute a background group or possibly a very small galactic cluster. More likely though, they are not sufficiently numerous or massive to constitute a true galactic cluster.

Ann
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Re: APOD: The Fornax Cluster of Galaxies (2022 Jan 29)

Post by Chris Peterson » Sat Jan 29, 2022 4:32 pm

Ann wrote: Sat Jan 29, 2022 4:22 pm Note that the background galaxies at upper left are all small and highly reddened. They are also close together, which is why I believe that they are gravitationally bound. They would therefore constitute a background group or possibly a very small galactic cluster. More likely though, they are not sufficiently numerous or massive to constitute a true galactic cluster.
Interesting distinction here. In common nomenclature, a (gravitationally bound) grouping of less than 50 or so galaxies is a "galaxy group". A grouping of a 100 or more is a "galaxy cluster". I guess between 50 and 100 is ambiguous.
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Re: APOD: The Fornax Cluster of Galaxies (2022 Jan 29)

Post by Fred the Cat » Sat Jan 29, 2022 4:37 pm

As the grand structure of the universe goes, what would be the order of things?

Cosmic background radiation>filaments and voids>super clusters>clusters>local group>Milky Way>solar system. It’s hard to organize these in my mind at the scale they are represented.

And what’s a cluster wall? :bang:
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Re: APOD: The Fornax Cluster of Galaxies (2022 Jan 29)

Post by Chris Peterson » Sat Jan 29, 2022 4:45 pm

Fred the Cat wrote: Sat Jan 29, 2022 4:37 pm As the grand structure of the universe goes, what would be the order of things?

Cosmic background radiation>filaments and voids>super clusters>clusters>local group>Milky Way>solar system. It’s hard to organize these in my mind at the scale they are represented.

And what’s a cluster wall? :bang:
You kind of went from generic to specific there. In general, CMB, filaments/voids, super clusters, galaxy clusters, galaxy groups, galaxies, stars (and maybe rogue planets), planetary systems, planets, moon systems, moons. Something like that sounds reasonable.

I think a galaxy wall is just a supercluster with a particular linear (or planar) structure.
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Re: APOD: The Fornax Cluster of Galaxies (2022 Jan 29)

Post by Fred the Cat » Sat Jan 29, 2022 6:31 pm

Chris Peterson wrote: Sat Jan 29, 2022 4:45 pm
Fred the Cat wrote: Sat Jan 29, 2022 4:37 pm As the grand structure of the universe goes, what would be the order of things?

Cosmic background radiation>filaments and voids>super clusters>clusters>local group>Milky Way>solar system. It’s hard to organize these in my mind at the scale they are represented.

And what’s a cluster wall? :bang:
You kind of went from generic to specific there. In general, CMB, filaments/voids, super clusters, galaxy clusters, galaxy groups, galaxies, stars (and maybe rogue planets), planetary systems, planets, moon systems, moons. Something like that sounds reasonable.

I think a galaxy wall is just a supercluster with a particular linear (or planar) structure.
Thanks! That helps me organize the big picture. My brain headed another way since but is still trying to get a mental image.

Reverting to the opposite direction (in my mind), the universe may not be geocentric but I wonder about the quantum world?

Wouldn’t it just be fitting if the smallest particles exhibit the “self-centeredness” that became the obvious description to early observers but an unlikely theorem modern quantum physicists might conceive; a universe evolving around each individual unit.

It certainly describes one compilation of particles – called a human. :wink:
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Re: APOD: The Fornax Cluster of Galaxies (2022 Jan 29)

Post by NCTom » Sun Jan 30, 2022 1:43 pm

Thanks all, for the comments and directions to find out more about Fornax and galaxy clusters in general.

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Re: APOD: The Fornax Cluster of Galaxies (2022 Jan 29)

Post by johnnydeep » Sun Jan 30, 2022 3:12 pm

"Galaxies in my pocket like grains of sand" - with a nod to Samuel R. Delany's novel.
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Re: APOD: The Fornax Cluster of Galaxies (2022 Jan 29)

Post by neufer » Sun Jan 30, 2022 10:35 pm

Chris Peterson wrote: Sat Jan 29, 2022 4:45 pm
Fred the Cat wrote: Sat Jan 29, 2022 4:37 pm
As the grand structure of the universe goes, what would be the order of things? Cosmic background radiation>filaments and voids>super clusters>clusters>local group>Milky Way>solar system. It’s hard to organize these in my mind at the scale they are represented.
You kind of went from generic to specific there. In general, CMB, filaments/voids, super clusters, galaxy clusters, galaxy groups, galaxies, stars (and maybe rogue planets), planetary systems, planets, moon systems, moons. Something like that sounds reasonable.
Let's go back from generic to specific again:

http://asterisk.apod.com/viewtopic.php? ... 05#p297205
https://en.wikipedia.org/wiki/GRB_190114C wrote: <<GRB 190114C was a notable gamma ray burst explosion from a galaxy 4.5 billion light years away (z=0.4245; magnitude=15.60est) near the Fornax constellation, that was initially detected in January 2019. The afterglow light emitted soon after the burst was found to be tera-electron volt radiation from inverse Compton emission, identified for the first time. According to the astronomers, "We observed a huge range of frequencies in the electromagnetic radiation afterglow of GRB 190114C. It is the most extensive to date for a gamma-ray burst." Also, according to other astronomers, "light detected from the object had the highest energy ever observed for a GRB: 1 Tera electron volt (TeV) -- about one trillion times as much energy per photon as visible light"; another source stated, "the brightest light ever seen from Earth [to date] ... [the] biggest explosion in the Universe since the Big Bang">>
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Re: APOD: The Fornax Cluster of Galaxies (2022 Jan 29)

Post by johnnydeep » Mon Jan 31, 2022 2:05 pm

Chris Peterson wrote: Sat Jan 29, 2022 4:45 pm
Fred the Cat wrote: Sat Jan 29, 2022 4:37 pm As the grand structure of the universe goes, what would be the order of things?

Cosmic background radiation>filaments and voids>super clusters>clusters>local group>Milky Way>solar system. It’s hard to organize these in my mind at the scale they are represented.

And what’s a cluster wall? :bang:
You kind of went from generic to specific there. In general, CMB, filaments/voids, super clusters, galaxy clusters, galaxy groups, galaxies, stars (and maybe rogue planets), planetary systems, planets, moon systems, moons. Something like that sounds reasonable.

I think a galaxy wall is just a supercluster with a particular linear (or planar) structure.
I don't understand the distinction you seem to be making here between generic (general?) and specific. To my my mind, all the things listed are just names for collections or classes of matter and energy determined primarily by how gravity acts, and so i would say that all are generic/general in nature (except for the CMB of which there is only one instance). The classes differ mainly in scale, and mass. A galaxy is a general thing, but an elliptical galaxy is a specific subclass of a galaxy. I wouldn't consider a galaxy to be any more or less generic or specific than a planet.
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Re: APOD: The Fornax Cluster of Galaxies (2022 Jan 29)

Post by Chris Peterson » Mon Jan 31, 2022 2:54 pm

johnnydeep wrote: Mon Jan 31, 2022 2:05 pm
Chris Peterson wrote: Sat Jan 29, 2022 4:45 pm
Fred the Cat wrote: Sat Jan 29, 2022 4:37 pm As the grand structure of the universe goes, what would be the order of things?

Cosmic background radiation>filaments and voids>super clusters>clusters>local group>Milky Way>solar system. It’s hard to organize these in my mind at the scale they are represented.

And what’s a cluster wall? :bang:
You kind of went from generic to specific there. In general, CMB, filaments/voids, super clusters, galaxy clusters, galaxy groups, galaxies, stars (and maybe rogue planets), planetary systems, planets, moon systems, moons. Something like that sounds reasonable.

I think a galaxy wall is just a supercluster with a particular linear (or planar) structure.
I don't understand the distinction you seem to be making here between generic (general?) and specific. To my my mind, all the things listed are just names for collections or classes of matter and energy determined primarily by how gravity acts, and so i would say that all are generic/general in nature (except for the CMB of which there is only one instance). The classes differ mainly in scale, and mass. A galaxy is a general thing, but an elliptical galaxy is a specific subclass of a galaxy. I wouldn't consider a galaxy to be any more or less generic or specific than a planet.
General: filaments and voids, super clusters, clusters.
Specific: local group, Milky Way, solar system.
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Re: APOD: The Fornax Cluster of Galaxies (2022 Jan 29)

Post by johnnydeep » Mon Jan 31, 2022 4:16 pm

Chris Peterson wrote: Mon Jan 31, 2022 2:54 pm
johnnydeep wrote: Mon Jan 31, 2022 2:05 pm
Chris Peterson wrote: Sat Jan 29, 2022 4:45 pm

You kind of went from generic to specific there. In general, CMB, filaments/voids, super clusters, galaxy clusters, galaxy groups, galaxies, stars (and maybe rogue planets), planetary systems, planets, moon systems, moons. Something like that sounds reasonable.

I think a galaxy wall is just a supercluster with a particular linear (or planar) structure.
I don't understand the distinction you seem to be making here between generic (general?) and specific. To my my mind, all the things listed are just names for collections or classes of matter and energy determined primarily by how gravity acts, and so i would say that all are generic/general in nature (except for the CMB of which there is only one instance). The classes differ mainly in scale, and mass. A galaxy is a general thing, but an elliptical galaxy is a specific subclass of a galaxy. I wouldn't consider a galaxy to be any more or less generic or specific than a planet.
General: filaments and voids, super clusters, clusters.
Specific: local group, Milky Way, solar system.
I see: "local group, Milky Way, solar system" were taken to be the names for the specific instances of the general "galaxy group, galaxy, solar system" classes that we happen to occupy. I guess I just ignored that as being not relevant. :-)
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