Mergers inside a ring

https://www.legacysurvey.org//viewer/?ra=117.8308&dec=50.2356&layer=ls-dr9&zoom=13

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whoa that is like so cool…

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It’s interesting how Sienna shows the two galaxies. Redshifts of .0228 vs .0238
Screen Shot 2022-05-19 at 4.32.08 PM

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Hahaha identical twins… :slight_smile: you zoom into these two peas in a pod and their active galactic nucleus seem to be octagonal… is that like an artifact of something like too much brightness coming from that region for the telescope or something else?
Legacy Survey Sky Browser

Yes, exactly, the centers saturate the detectors.

Ahh I think you helped me find something, or find nothing depending on how you look at it, by turning on residuals. :wink:

but I wonder how related this galaxy that Ernest found is related to ring galaxies in general. What point were you making about the redshifts?

@ernest would you say that this is a collisonal ring structure?

I was just showing how the two galaxies are indeed merging with very similar redshifts. Why don’t elliptical galaxies get “torn apart” when interacting like spirals do?

Oh okay @jim_c @Ernest there is another sort-of-similar one. Check it out!
https://www.legacysurvey.org/viewer?ra=180.1864&dec=-0.1561&layer=hsc-dr2&zoom=15

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@jim_c well I don’t know why exactly they don’t get torn apart, but here is some of what I’ve read and a guess

I have read that elliptical galaxies have actually lost their dust and have little structure, potentially formed by mergers already. Their old stars, no longer powered by the cycle of dust/supernova in a typical spiral galaxy, wander aimlessly locked in respect to their dense center, sometimes in-falling to the center, other times accreting at the center, and other times precessing in a random orientation, but relatively random and in a steady-state. So actually when two elliptical galaxies collide, it is apparently unlikely for any star to collide with any other star because there is just so much space between the stars, and since the galaxies have little dust, really what is going on during the collision? Not a whole lot, indeed, there are no starbursts to fuel a promiscuous interaction. However, the elliptical galaxy may gain structure in their interaction if it consumes a galaxy with sufficient dust, look at these shells and as we browse the skies, we will find these sort of “post merger ellipses” but importantly, apparently, the structure of this dust comes from the other galaxy.

Or maybe forming an ultra-massive object allows accretion of the dust into the galaxy from the interstellar medium. Would that explain the shells in Ernest’s beautiful picture above? I don’t know, but that is a really cool merging galaxy. Don’t you think?
image

On the other hand, spiral galaxies are dust filled whose stars move about in ordered radial motion, along ripples of stellar density; their logspiral arms contain dust and stellar nurseries, actually just like dense nuclear star cluster centers. But they too are pinpointed on a blackhole, which accretes dust and stars. At low masses, the center is populated by stars which existed in globular clusters. But what is a globular cluster? There is some evidence that it is a gobbled galaxy; some of them are fossil fragments formed long ago in the early universe, others of them are nuclear star clusters of galaxies long ago, potentially held together by their own dark matter, and have been sitting in galaxies for many years, as evidenced by a difference in metallicity. It seems that dark matter must play a role in galactic collision and in holding galactic components together; I assume in simulations without dark matter there are many fewer collisions, but idk

However, why does the structure of log spiral galaxies get disfigured if in two colliding galaxies, no individual star collision is expected? It is clear to see that should be the case with the dust, but how about the stars. That is basically the limit of my knowledge. If spirals form due in part to their dense centers, why don’t globular clusters start forming spiral arms in other galaxies, especially when they start growing a blackhole?

After a while the ellipse becomes this cosmic ghostown, whose final fate is maybe even more chilling, the slow conversion into the widening gyre that was once their chernobyl, for indeed, at the center of star clusters, there still lies the faint blue glow of a stellar nursery especially when the host galaxy mass is more than 10^9 solar masses, and when velocity dispersion is>40km/s of their stars, they lead to the runaway growth of a supermassive black hole, as evidenced by twice than expected X-ray detection, but there is some circularity to that, since are the blackholes causing the velocity dispersion or is the velocity dispersion allowing the growth of the blackhole. Nonetheless, the nice elliptical structure may be “destroyed” during some mergers because it could trigger the runaway growth of a blackhole (maybe?) so not torn apart, but imploded … idk anyways

The merger between two elliptical galaxies, without dust, is called a dry merger because it doesn’t result in starbursts from supernova ejections due to interaction. I would say it is a little more wet because there isn’t dust :wink: but there is a thought that these are sorts of almost collisionless collisions. However,

But when we look at them, we see diffuse balls of starlight. When we look at spirals we see many features, but the ones I will focus on are the spiral arms, which are ripples of star density, log ripples.

Who knows if we even see anything interesting from a collision of two ellipticals? But I still think they’re beautiful.

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Really nteresting read @DarK_OmEgA . With some further reading I have learned that elliptical galaxies do not rotate like spirals do, so that would seem to be a major factor for the lack of apparent interactive “destruction” we see compared to spiral mergers.

Yes maybe. I think this is how the Hoag’s object may have formed, any thoughts? :smiley:

Interestingly, this galaxy was part of the Gems of the Galaxy Zoo program see this paper: https://iopscience.iop.org/article/10.3847/1538-3881/ac517d/pdf

It’s in Figure 9 page 15