APOD: Simulation: A Disk Galaxy Forms (2023 May 31)

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APOD: Simulation: A Disk Galaxy Forms (2023 May 31)

Post by APOD Robot » Wed May 31, 2023 4:08 am

Image Simulation: A Disk Galaxy Forms

Explanation: How did we get here? We know that we live on a planet orbiting a star orbiting a galaxy, but how did all of this form? Since our universe moves too slowly to watch, faster-moving computer simulations are created to help find out. Specifically, this featured video from the IllustrisTNG collaboration tracks gas from the early universe (redshift 12) until today (redshift 0). As the simulation begins, ambient gas falls into and accumulates in a region of relatively high gravity. After a few billion years, a well-defined center materializes from a strange and fascinating cosmic dance. Gas blobs -- some representing small satellite galaxies -- continue to fall into and become absorbed by the rotating galaxy as the present epoch is reached and the video ends. For the Milky Way Galaxy, however, big mergers may not be over -- recent evidence indicates that our large spiral disk Galaxy will collide and coalesce with the slightly larger Andromeda spiral disk galaxy in the next few billion years.

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Re: APOD: Simulation: A Disk Galaxy Forms (2023 May 31)

Post by AVAO » Wed May 31, 2023 5:19 am

APOD Robot wrote: Wed May 31, 2023 4:08 am Image Simulation: A Disk Galaxy Forms

Explanation: How did we get here? We know that we live on a planet orbiting a star orbiting a galaxy, but how did all of this form? Since our universe moves too slowly to watch, faster-moving computer simulations are created to help find out. Specifically, this featured video from the IllustrisTNG collaboration tracks gas from the early universe (redshift 12) until today (redshift 0). As the simulation begins, ambient gas falls into and accumulates in a region of relatively high gravity. After a few billion years, a well-defined center materializes from a strange and fascinating cosmic dance. Gas blobs -- some representing small satellite galaxies -- continue to fall into and become absorbed by the rotating galaxy as the present epoch is reached and the video ends. For the Milky Way Galaxy, however, big mergers may not be over -- recent evidence indicates that our large spiral disk Galaxy will collide and coalesce with the slightly larger Andromeda spiral disk galaxy in the next few billion years.

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Well. The video shown is visually very high-quality and is intended to illustrate the formation of galaxies according to the cosmological standard model using a state-of-the-art simulation (supercomputing). Well. Astronomy outside of our solar system is astroarchaeology. It is based on one-way communication from the past and we will therefore never be able to carry out experiments in a single human generation. For astronomy as a science, this is a huge problem, since in all other sciences, only what can be experimentally verified or repeated is considered scientifically recognized. Simulations are trying to fill this huge gap in astronomy. For this purpose, first cosmological models are developed, such as the cosmological standard model from the big bang to the present day, and then "checked" using mathematically based simulations. Well. Scientific simulations, regardless of the computing power, are always the result of the previously defined framework parameters. This means that if we want to discuss simulations, we should always first talk about the framework parameters before we talk about the content or the result of the simulation. If I change this parameters, I can generate practically any result. Unfortunately, it is precisely this point, which is decisive for everything, that is not, or at least not comprehensively, comprehensible in many scientific papers. A scientific simulation can therefore inherently never be scientifically completely neutral or completely objective...

Wikipedia: The Illustris project is one of the world's largest continuous astrophysical simulation series, which a team of internationally collaborating scientists has been conducting since 2011. The aim is to explore the processes of formation and evolution of the galaxy in the universe using a comprehensive physical model... In 2018 the Illustris team released an update of the Illustris simulation called Illustris "The Next Generation" (TGN). The Illustris simulation framework and galaxy formation model have been used for numerous spin-off projects: Auriga (2017), IllustrisTNG (2017), Thesan (2021), MillenniumTNG (2022) and TNG-Cluster (announced for 2023). TGN50 shows a clipping of 50 Mpc TGN100 a clipping of 100 Mpc. Well.

It's 2023 and the James Webb Space Telescope is showing something else. I'm curious how the next generation of the next generation simulations will look like ;-)

https://apod.nasa.gov/apod/ap120717.html

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Re: APOD: Simulation: A Disk Galaxy Forms (2023 May 31)

Post by Chris Peterson » Wed May 31, 2023 5:49 am

AVAO wrote: Wed May 31, 2023 5:19 am
APOD Robot wrote: Wed May 31, 2023 4:08 am Image Simulation: A Disk Galaxy Forms

Explanation: How did we get here? We know that we live on a planet orbiting a star orbiting a galaxy, but how did all of this form? Since our universe moves too slowly to watch, faster-moving computer simulations are created to help find out. Specifically, this featured video from the IllustrisTNG collaboration tracks gas from the early universe (redshift 12) until today (redshift 0). As the simulation begins, ambient gas falls into and accumulates in a region of relatively high gravity. After a few billion years, a well-defined center materializes from a strange and fascinating cosmic dance. Gas blobs -- some representing small satellite galaxies -- continue to fall into and become absorbed by the rotating galaxy as the present epoch is reached and the video ends. For the Milky Way Galaxy, however, big mergers may not be over -- recent evidence indicates that our large spiral disk Galaxy will collide and coalesce with the slightly larger Andromeda spiral disk galaxy in the next few billion years.

<< Previous APOD This Day in APOD Next APOD >>

Well. The video shown is visually very high-quality and is intended to illustrate the formation of galaxies according to the cosmological standard model using a state-of-the-art simulation (supercomputing). Well. Astronomy outside of our solar system is astroarchaeology. It is based on one-way communication from the past and we will therefore never be able to carry out experiments in a single human generation. For astronomy as a science, this is a huge problem, since in all other sciences, only what can be experimentally verified or repeated is considered scientifically recognized. Simulations are trying to fill this huge gap in astronomy. For this purpose, first cosmological models are developed, such as the cosmological standard model from the big bang to the present day, and then "checked" using mathematically based simulations. Well. Scientific simulations, regardless of the computing power, are always the result of the previously defined framework parameters. This means that if we want to discuss simulations, we should always first talk about the framework parameters before we talk about the content or the result of the simulation. If I change this parameters, I can generate practically any result. Unfortunately, it is precisely this point, which is decisive for everything, that is not, or at least not comprehensively, comprehensible in many scientific papers. A scientific simulation can therefore inherently never be scientifically completely neutral or completely objective...

Wikipedia: The Illustris project is one of the world's largest continuous astrophysical simulation series, which a team of internationally collaborating scientists has been conducting since 2011. The aim is to explore the processes of formation and evolution of the galaxy in the universe using a comprehensive physical model... In 2018 the Illustris team released an update of the Illustris simulation called Illustris "The Next Generation" (TGN). The Illustris simulation framework and galaxy formation model have been used for numerous spin-off projects: Auriga (2017), IllustrisTNG (2017), Thesan (2021), MillenniumTNG (2022) and TNG-Cluster (announced for 2023). TGN50 shows a clipping of 50 Mpc TGN100 a clipping of 100 Mpc. Well.

It's 2023 and the James Webb Space Telescope is showing something else. I'm curious how the next generation of the next generation simulations will look like ;-)

https://apod.nasa.gov/apod/ap120717.html
Almost all modern science is based upon simulations which are then tested against observation. Astronomy is no different.
Chris

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Re: APOD: Simulation: A Disk Galaxy Forms (2023 May 31)

Post by Christian G. » Wed May 31, 2023 2:03 pm

This video is more than fascinating, I find it emotionally moving.
(well chosen music on top of it! which I usually turn off to watch in silence but not this time)

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Re: APOD: Simulation: A Disk Galaxy Forms (2023 May 31)

Post by JohnD » Wed May 31, 2023 3:58 pm

What a sparse explanation to this most involved and involving video!

Ok, it starts at "Redshift 12", which is how long ago? And ends at "Redshift 0", but no scale or mete is shown. But several do appear with no explanation; "LogM* which increases, "SFR" in "M.yr-1" which varies, "z" which falls. The video start with three subframes in the picture, but with no explanation, and goes are times in to split screen, displaying different wavelengths?? No explanation! One of these goes full screen with a scale of "Gas metallicity" - a measure of the forging of heavier elements as stars age and die, perhaps? More, better explanation, please!
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Re: APOD: Simulation: A Disk Galaxy Forms (2023 May 31)

Post by Chris Peterson » Wed May 31, 2023 4:07 pm

JohnD wrote: Wed May 31, 2023 3:58 pm What a sparse explanation to this most involved and involving video!

Ok, it starts at "Redshift 12", which is how long ago? And ends at "Redshift 0", but no scale or mete is shown. But several do appear with no explanation; "LogM* which increases, "SFR" in "M.yr-1" which varies, "z" which falls. The video start with three subframes in the picture, but with no explanation, and goes are times in to split screen, displaying different wavelengths?? No explanation! One of these goes full screen with a scale of "Gas metallicity" - a measure of the forging of heavier elements as stars age and die, perhaps? More, better explanation, please!
John
Redshift is the primary measurement used to assess cosmological distance and time. It can yield different value for both distance and time, based on certain assumptions (and even on the definition of distance used). So it's a bit difficult to assign values like these in a way that is safely accurate. Hence redshift, which is an absolute measurement. I suggest using an online redshift calculator. I like https://www.astro.ucla.edu/~wright/CosmoCalc.html , where you can play with the value of the Hubble constant (or take the default) plug in a Z value, and calculate for a (usually) flat universe. This will give you values for what are probably the most interesting measurements you are looking for: age at redshift, light travel time, and comoving radial distance (how far away the source location currently lies, given the expansion of spacetime as the light was traveling to us).
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Re: APOD: Simulation: A Disk Galaxy Forms (2023 May 31)

Post by AVAO » Wed May 31, 2023 5:27 pm

JohnD wrote: Wed May 31, 2023 3:58 pm What a sparse explanation to this most involved and involving video!

Ok, it starts at "Redshift 12", which is how long ago? And ends at "Redshift 0", but no scale or mete is shown. But several do appear with no explanation; "LogM* which increases, "SFR" in "M.yr-1" which varies, "z" which falls. The video start with three subframes in the picture, but with no explanation, and goes are times in to split screen, displaying different wavelengths?? No explanation! One of these goes full screen with a scale of "Gas metallicity" - a measure of the forging of heavier elements as stars age and die, perhaps? More, better explanation, please!
John
"Formation of a single galaxy "g3", tracked through time from high redshift until the present day. This relatively "average" TNG50 galaxy will be just slightly less massive than our own Milky Way at z=0. We include a large-scale view (lower left), and zoomed in views of the central gas and stellar structures (lower right), while the main panel shows projected gas density. At z=1.5 we pause and rotate around the system, showing in order: gas metallicity, gas velocity field, and H-alpha luminosity, before continuing. What is a small dwarf at high redshift (108.3 solar masses in stars at z=4) transitions, at late times, into a large stable disk with a quasi-steady star formation rate of a few solar masses per year."

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Re: APOD: Simulation: A Disk Galaxy Forms (2023 May 31)

Post by Rauf » Wed May 31, 2023 7:38 pm

Chris Alex wrote: Wed May 31, 2023 2:03 pm This video is more than fascinating, I find it emotionally moving.
(well chosen music on top of it! which I usually turn off to watch in silence but not this time)
Yeah, to think how many years it takes for a galaxy to form, from basically sub-atomic particles to atoms and nebulae and stars and planets, and to life.
Watching matter interact and twist until a core forms, and some other core merges to form a bigger core, and more gas and dust swirling in a cosmic dance, I don't think my words do justice to describe it at all. That lovely music is way better, because sometimes when words fail, music steps up.
How small we are.

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Re: APOD: Simulation: A Disk Galaxy Forms (2023 May 31)

Post by VictorBorun » Wed May 31, 2023 8:17 pm

AVAO wrote: Wed May 31, 2023 5:27 pm
JohnD wrote: Wed May 31, 2023 3:58 pm What a sparse explanation to this most involved and involving video!

Ok, it starts at "Redshift 12", which is how long ago? And ends at "Redshift 0", but no scale or mete is shown. But several do appear with no explanation; "LogM* which increases, "SFR" in "M.yr-1" which varies, "z" which falls. The video start with three subframes in the picture, but with no explanation, and goes are times in to split screen, displaying different wavelengths?? No explanation! One of these goes full screen with a scale of "Gas metallicity" - a measure of the forging of heavier elements as stars age and die, perhaps? More, better explanation, please!
John
"Formation of a single galaxy "g3", tracked through time from high redshift until the present day. This relatively "average" TNG50 galaxy will be just slightly less massive than our own Milky Way at z=0. We include a large-scale view (lower left), and zoomed in views of the central gas and stellar structures (lower right), while the main panel shows projected gas density. At z=1.5 we pause and rotate around the system, showing in order: gas metallicity, gas velocity field, and H-alpha luminosity, before continuing. What is a small dwarf at high redshift (108.3 solar masses in stars at z=4) transitions, at late times, into a large stable disk with a quasi-steady star formation rate of a few solar masses per year."
Oh thanks! Only now I get to switch YouTube to FullScreen, stop eclipsing the bottom part with video clip time navigator bar and see every scale you mention.

Baby Milky Way in H-alpha, has already grown some blue giants!
Image

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Re: APOD: Simulation: A Disk Galaxy Forms (2023 May 31)

Post by orin stepanek » Thu Jun 01, 2023 12:25 am

M31vsMW_nasa_960.jpg
I won't worry about Andromeda Colliding with the MW until they get
in range! :mrgreen:
51ZjBEW+qNL.jpg
Kitty is so cute!
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Smile today; tomorrow's another day!

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Re: APOD: Simulation: A Disk Galaxy Forms (2023 May 31)

Post by Ann » Thu Jun 01, 2023 4:18 am

The simulation seems to show that the Universe likes to make spiral galaxies. So where do all the ellipticals come from?
Space.com wrote:

Astronomers have identified more spiral galaxies than ellipticals, but that's simply because the spirals are easier to spot. While spiral galaxies are bright, elliptical galaxies are dim. Spiral galaxies are hotbeds of star formation, but elliptical galaxies aren't nearly as prolific because they contain less gas and dust, which means fewer new (and brighter) stars are born. The existing stars inside an elliptical galaxy tend to be older, giving off more red light than younger stars.

So, why do astronomers think elliptical galaxies dominate the sky? Because when specific regions of the sky are studied in depth, more elliptical galaxies appear. Astronomers think such counts are consistent throughout the universe.
...

A supermassive black hole is thought to lie at the center of these ancient galaxies. These gluttonous giants consume gas and dust, and may play a role in the slower growth of elliptical galaxies.

Born from collision, elliptical galaxies are more commonly found around clusters and groups of galaxies. They are less frequently spotted in the early universe, which supports the idea that they evolved from the collisions that came later in the life of a galaxy.
Dry merger IC 1181 IC 1178 Detlef Hartmann.png
A "dry" merger between two gas-poor galaxies.
Photo: Detlef Hartmann.

So mergers are a very common cause of the formation of elliptical galaxies. Ellipticals dominate almost all rich galaxy clusters:

Hubblesite.org wrote about the spiral galaxy falling into galaxy cluster Abell 2667:

NASA's Hubble Space Telescope, in collaboration with several other ground- and space- based telescopes, has captured a galaxy being ripped apart by a galaxy cluster's gravitational field and harsh environment.

The finding sheds light on the mysterious process by which gas-rich spiral-shaped galaxies might evolve into gas-poor irregular- or elliptical-shaped galaxies over billions of years. The new observations also reveal one mechanism for forming the millions of "homeless" stars seen scattered throughout galaxy clusters.

There are many galaxies of different shapes and sizes around us today. Roughly half are gas-poor elliptical-shaped galaxies with little new star formation activity, and half are gas- rich spiral and irregular galaxies with high star formation activity. Observations have shown that gas-poor galaxies are most often found near the centers of crowded galaxy clusters, whereas spirals spend most of their lifetimes in less crowded circumstances.

But deep observations of the universe show that when the universe was half its present age, only one in five galaxies was a gas-poor object. So where do all of today's gas-poor galaxies come from? Scientists suspect that some kind of transformative process must have taken place, but because galaxy evolution occurs over billions of years, they previously have not been able to see this transformation at work...
The hapless spiral is losing its gas because it is falling through the blisteringly hot intracluster medium of Abell 2667. In the process it is losing bits and pieces of itself, which in time may evolve into dwarf elliptical galaxies. And in a billion years or so, the spiral galaxy falling into Abell 2667 will be indistinguishable from all the other yellow blobs of large galaxy clusters.

And one mechanism that destroys spiral galaxies and turns them into ellipticals in large galaxy clusters is the violent outbursts of ultramassive black holes in the largest elliptical galaxies:


Ann
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Re: APOD: Simulation: A Disk Galaxy Forms (2023 May 31)

Post by VictorBorun » Thu Jun 01, 2023 7:57 am

Ann wrote: Thu Jun 01, 2023 4:18 am The simulation seems to show that the Universe likes to make spiral galaxies. So where do all the ellipticals come from?

And one mechanism that destroys spiral galaxies and turns them into ellipticals in large galaxy clusters is the violent outbursts of ultramassive black holes in the largest elliptical galaxies: Ann
Do I get it right:

1) If Local Leaf i. e. Local Cluster + Council of Giants has more spiral members than elliptical ones, it's just that this supercluster and clusters are small. In normal clusters like Virgo the galaxies population is mostly elliptical

2) Gravitation struggles to feed galaxies in a smooth way. Once a few billion suns BH forms, it tends to blow the hydrogen+dust interstellar media out of the galaxy and stop the star formation for good

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Re: APOD: Simulation: A Disk Galaxy Forms (2023 May 31)

Post by madtom1999 » Thu Jun 01, 2023 8:37 am

Is there any FLOSS software I can use to play with this stuff at home?

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Re: APOD: Simulation: A Disk Galaxy Forms (2023 May 31)

Post by gmPhil » Thu Jun 01, 2023 9:11 am

madtom1999 wrote: Thu Jun 01, 2023 8:37 am Is there any FLOSS software I can use to play with this stuff at home?
Play with what, exactly - what are you wanting to do?

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Re: APOD: Simulation: A Disk Galaxy Forms (2023 May 31)

Post by johnnydeep » Thu Jun 01, 2023 12:42 pm

Non-sequitur: hey, where's the APOD for 6/1? Nothing at https://apod.nasa.gov/apod/ap230601.html yet...
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Re: APOD: Simulation: A Disk Galaxy Forms (2023 May 31)

Post by Rauf » Thu Jun 01, 2023 1:04 pm

johnnydeep wrote: Thu Jun 01, 2023 12:42 pm Non-sequitur: hey, where's the APOD for 6/1? Nothing at https://apod.nasa.gov/apod/ap230601.html yet...
I'm thinking the same. I hope dear editor is okay! :?

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Re: APOD: Simulation: A Disk Galaxy Forms (2023 May 31)

Post by johnnydeep » Thu Jun 01, 2023 3:29 pm

Rauf wrote: Thu Jun 01, 2023 1:04 pm
johnnydeep wrote: Thu Jun 01, 2023 12:42 pm Non-sequitur: hey, where's the APOD for 6/1? Nothing at https://apod.nasa.gov/apod/ap230601.html yet...
I'm thinking the same. I hope dear editor is okay! :?
I see it's been "fixed"!
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Re: APOD: Simulation: A Disk Galaxy Forms (2023 May 31)

Post by Ann » Thu Jun 01, 2023 6:08 pm

VictorBorun wrote: Thu Jun 01, 2023 7:57 am
Ann wrote: Thu Jun 01, 2023 4:18 am The simulation seems to show that the Universe likes to make spiral galaxies. So where do all the ellipticals come from?

And one mechanism that destroys spiral galaxies and turns them into ellipticals in large galaxy clusters is the violent outbursts of ultramassive black holes in the largest elliptical galaxies: Ann
Do I get it right:

1) If Local Leaf i. e. Local Cluster + Council of Giants has more spiral members than elliptical ones, it's just that this supercluster and clusters are small. In normal clusters like Virgo the galaxies population is mostly elliptical

2) Gravitation struggles to feed galaxies in a smooth way. Once a few billion suns BH forms, it tends to blow the hydrogen+dust interstellar media out of the galaxy and stop the star formation for good

As to your first question, yes, in our neck of the woods, there is actually just one major elliptical galaxy, Maffei 1!
Wikipedia wrote:

Maffei 1 is a massive elliptical galaxy in the constellation Cassiopeia. Once believed to be a member of the Local Group of galaxies, it is now known to belong to a separate group, the IC 342/Maffei Group....

Maffei 1 is situated at an estimated distance of 3–4 Mpc from the Milky Way. It may be the closest giant elliptical galaxy...

Maffei 1 lies in the Zone of Avoidance and is heavily obscured by the Milky Way's stars and dust. If it were not obscured, it would be one of the largest (about 3/4 the size of the full moon), brightest, and best-known galaxies in the sky...

The total visible absolute magnitude of Maffei 1, MV=−20.8, is comparable to that of the Milky Way.

Yes, but apart from Maffei 1, all the reasonably large galaxies in and close to the Local Group are spirals:


Even Maffei 2, another member of the Maffei/IC 342 group, is a spiral:


So, yeah. All the reasonably large galaxies in and near the Local Group of galaxies are spirals, all but one, Maffei 1.


But let's look at the major galaxies of another nearby group, the M81 group:


While M81 is a picture-perfect grand design galaxy, M82 is a contorted object wildly spewing gas into its surroundings from runaway star formation in its core. Apparently interactions with M81 drove much or most of the gas in M82 into the Cigar galaxy's center, where all this gas set off a wildfire of star formation. So while the disk of M82 is both chaotic and turbulent and apparently not forming any stars at all, the center is forming stars at a rate that can't possibly leave the galaxy "unscathed". My guess is that M82 will end up as a lenticular galaxy, a "strangled" galaxy with a disk but with no gas or star formation.

M81 is bigger than M82. The bigger bully "won".

In large galaxy clusters, almost every galaxy is close to another galaxy that can be described as a bigger bully. Being close to a big bully isn't good for a galaxy's elegant spiral shape. So how did Maffei 1 ended up as a giant elliptical galaxy, when this galaxy can only be described as its own biggest bully? Maffei 1 hasn't even got an active galactic nucleus, no feeding black hole and no jet. Don't ask me what made it "go elliptical"!

A sparse and empty surroundings may be good for a galaxy that wants to do things its own way. Like UGC 1382.


UGC 1382, living its life in splendid isolation unbothered by any big galactic bullies, has picked up passing galactic driftwood and flotsam and incorporated these pieces into itself. Now it is gigantic, with a diameter of some 718,000 light-years. That's aaa-mazing!!!

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Re: APOD: Simulation: A Disk Galaxy Forms (2023 May 31)

Post by VictorBorun » Fri Jun 02, 2023 12:49 am

Ann wrote: Thu Jun 01, 2023 6:08 pm A sparse and empty surroundings may be good for a galaxy that wants to do things its own way. Like UGC 1382. UGC 1382, living its life in splendid isolation unbothered by any big galactic bullies, has picked up passing galactic driftwood and flotsam and incorporated these pieces into itself. Now it is gigantic, with a diameter of some 718,000 light-years. That's aaa-mazing!!!
Ann
The last example seems to hint that every distant elliptic galaxy may in fact be the core of an understudied disk galaxy…

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Re: APOD: Simulation: A Disk Galaxy Forms (2023 May 31)

Post by Ann » Fri Jun 02, 2023 5:56 am

VictorBorun wrote: Fri Jun 02, 2023 12:49 am
Ann wrote: Thu Jun 01, 2023 6:08 pm A sparse and empty surroundings may be good for a galaxy that wants to do things its own way. Like UGC 1382. UGC 1382, living its life in splendid isolation unbothered by any big galactic bullies, has picked up passing galactic driftwood and flotsam and incorporated these pieces into itself. Now it is gigantic, with a diameter of some 718,000 light-years. That's aaa-mazing!!!
Ann
The last example seems to hint that every distant elliptic galaxy may in fact be the core of an understudied disk galaxy…
Well, there is a similar example.


Like UGC 1382, galaxy Malin 1 has a smallish, all yellow, non-starforming and reasonably bright inner disk. But then both galaxies have a huge set of very low-surface brightness spiral arms. The approximate size of Malin 1, including its faint spiral arms, is some 650,000 light-years, which actually makes it a bit smaller than UGC 1382.
Wikipedia wrote:

Malin 1 was found later to be interacting with two other galaxies, Malin 1B and SDSS J123708.91+142253.2. Malin 1B is located 46,000 light-years (14,000 pc) away from the high surface brightness central spiral of Malin 1, which may be responsible for the formation of the galaxy's central bar. Meanwhile, SDSS J123708.91+142253.2 is located within the huge, faint halo of Malin 1 and might have caused the formation of the extended low surface brightness disc through tidal stripping.
Yeah. Whatever.

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Re: APOD: Simulation: A Disk Galaxy Forms (2023 May 31)

Post by VictorBorun » Fri Jun 02, 2023 3:43 pm

Ann wrote: Fri Jun 02, 2023 5:56 am
VictorBorun wrote: Fri Jun 02, 2023 12:49 am
Ann wrote: Thu Jun 01, 2023 6:08 pm A sparse and empty surroundings may be good for a galaxy that wants to do things its own way. Like UGC 1382. UGC 1382, living its life in splendid isolation unbothered by any big galactic bullies, has picked up passing galactic driftwood and flotsam and incorporated these pieces into itself. Now it is gigantic, with a diameter of some 718,000 light-years. That's aaa-mazing!!!
Ann
The last example seems to hint that every distant elliptic galaxy may in fact be the core of an understudied disk galaxy…
Well, there is a similar example.


Like UGC 1382, galaxy Malin 1 has a smallish, all yellow, non-starforming and reasonably bright inner disk. But then both galaxies have a huge set of very low-surface brightness spiral arms. The approximate size of Malin 1, including its faint spiral arms, is some 650,000 light-years, which actually makes it a bit smaller than UGC 1382.
Wikipedia wrote:

Malin 1 was found later to be interacting with two other galaxies, Malin 1B and SDSS J123708.91+142253.2. Malin 1B is located 46,000 light-years (14,000 pc) away from the high surface brightness central spiral of Malin 1, which may be responsible for the formation of the galaxy's central bar. Meanwhile, SDSS J123708.91+142253.2 is located within the huge, faint halo of Malin 1 and might have caused the formation of the extended low surface brightness disc through tidal stripping.
Yeah. Whatever.

Ann
Then there is a chance to tell one way or the other how the galaxy population is nowadays: to look if every unmasked impostor with giant dim disk and large bright core is well isolated from crowded clusters of large galaxies.