APOD: Recycling NGC 5291 (2015 Nov 21)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 3548
Joined: Fri Dec 04, 2009 3:27 am

APOD: Recycling NGC 5291 (2015 Nov 21)

Post by APOD Robot » Sat Nov 21, 2015 5:12 am

Image Recycling NGC 5291

Explanation: Following an ancient galaxy-galaxy collision 200 million light-years from Earth, debris from a gas-rich galaxy, NGC 5291, was flung far into intergalactic space. NGC 5291 and the likely interloper, also known as the "Seashell" galaxy, are captured near the center of this spectacular scene. The sharp, ground-based telescopic image looks toward the galaxy cluster Abell 3574 in the southern constellation Centaurus. Stretched along the 100,000 light-year long tidal tails, are clumps resembling dwarf galaxies, but lacking old stars, apparently dominated by young stars and active star forming regions. Found to be unusually rich in elements heavier than hydrogen and helium, the dwarf galaxies were likely born in intergalactic space, recycling the enriched debris from NGC 5291 itself.

<< Previous APOD This Day in APOD Next APOD >>
[/b]

User avatar
Ann
4725 Å
Posts: 9516
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Recycling NGC 5291 (2015 Nov 21)

Post by Ann » Sat Nov 21, 2015 7:10 am

Today's APOD is a truly fascinating portrait of the effects of a galactic collision that I personally had never heard of before. I have found a few pictures that might shed some light on what is going on.
Ejected gas from NGC 5291 and its interloper.
Credit: P-A Duc, CEA-CNRS/NRAO/AUI/NSF/NASA.
The picture at left shows gas that has been ejected from the interaction between NGC 5291 and its interloper, the Seashell galaxy. The ejected gas forms a huge ring. Where the gas is more concentrated, dwarf galaxies have formed.
NGC 5291, the Seashell galaxy and surrounding material.
Photo: Spitzer Space Telescope.













At right is a Spitzer Space Telescope infrared image of the same region. Stars are shown as cyan-colored, while dust is red. The larger galaxy, NGC 5291, contains some dust, which can be seen in the Spitzer image as a faint red ring around its center. In today's APOD, the dust is very obvious. (The dwarf galaxies that have formed in the ejected gas stream are very red from warm dust.)

But the Seashell galaxy is "all blue" in the Spitzer image. It contains no concentrated pockets of dust at all. Virtually all dust and gas has been driven out of the Seashell galaxy.

To me, the most amazing object in today's APOD is the Seashell galaxy. This small galaxy contains no gas or dust, is all yellow and has an amazing, elegantly curving and "sharp-edged" shape, almost like a cosmic cutout. It is so different from the typical yellow elliptical "blob". But because of its yellow color and perfectly smooth "brightness profile", it is also so different from a typical spiral galaxy.
NGC 5216 and 5218.
Photo: Martin Winder, Dietmar Hager.
I can't resist comparing The Seashell galaxy to NGC 5218, one of the two interacting galaxies in what is known as Keenan's system. NGC 5218 has bluish arcs surrounding a yellow bulge. The arcs are sharp-edged and smooth. They contain no star clusters or dust patches at all. The bluish arcs are the remains of previous star formation. Their smooth shape and lack of dust shows that no new stars are forming there today. The stars in the arc are likely about one to two billion years old, and their shape is likely caused by a mixture of normal interactions of components in a spiral galaxy and interactions with NGC 5216.

But the stars in the Seashell galaxy must be much older. The Seashell must have given up all star formation several billion years ago. Note that the entire galaxy is the same yellow color. How can its strange shape be explained?

I think the Seashell is an example of strong tidal forces acting on a relatively small and lightweight elliptical galaxy. The fantastic shape of it must be caused by gravity acting differently on different parts of it. In fact, the Seashell shows a ring-like structure which is not unlike the huge gas ring emanating from the interaction between NGC 5291 and the Seashell, and the "ring" of the Seashell is oriented in more or less the same direction as the huge gas ring.

What a truly fantastic APOD!

Ann
Color Commentator

bls0326
Ensign
Posts: 82
Joined: Tue Mar 26, 2013 10:18 pm

Re: APOD: Recycling NGC 5291 (2015 Nov 21)

Post by bls0326 » Sat Nov 21, 2015 2:52 pm

+1 fantastic APOD.

Ann, thanks for the additional pictures and info. It really adds to already interesting APOD.

User avatar
neufer
Vacationer at Tralfamadore
Posts: 15967
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Recycling NGC 5291 (2015 Nov 21)

Post by neufer » Sat Nov 21, 2015 3:32 pm

APOD Robot wrote:
NGC 5291 and the likely interloper, also known as the "Seashell" galaxy,
are captured near the center of this spectacular scene.

"Seashell" galaxy :?: More like the "Hair Blower" galaxy.

Interloper, n. [Pref. inter- + D. looper a runner, fr. loopen to run; akin to E. leap. cf. Elope.] One who unlawfully intrudes upon a property, a station, or an office; one who interferes wrongfully or officiously.
https://en.wikipedia.org/wiki/Interlopers wrote:
<<Interlopers is a 2001 science fiction novel by Alan Dean Foster. The story centers on Cody Westcott, a young archeologist, who returns from a dig at Apachetarimac having studied the Chachapoyansthat race. In an attempt to reconstruct an ancient potion whose ingredients he discovers in the dig, his friend is murdered and he ends up drinking the only sample. He discovers that he can "see" strange creatures inhabiting the world, and that these creatures harm humans and cause feelings of hate and anger upon which they feed and multiply.>>
Art Neuendorffer

Boomer12k
:---[===] *
Posts: 2485
Joined: Sun Apr 22, 2007 12:07 am

Re: APOD: Recycling NGC 5291 (2015 Nov 21)

Post by Boomer12k » Sat Nov 21, 2015 6:01 pm

I would think it reasonable to expect heavier elements in the star forming dwarf galaxies....many supernova probably have taken place producing the heavier elements, that are then recycled...Our Sun is such a Star, said to be 3rd Generation....totally reasonable, I would think for such a Star Factory situation.

Really good image!!
:---[===] *

User avatar
Chris Peterson
Abominable Snowman
Posts: 14354
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Recycling NGC 5291 (2015 Nov 21)

Post by Chris Peterson » Sat Nov 21, 2015 6:29 pm

Boomer12k wrote:I would think it reasonable to expect heavier elements in the star forming dwarf galaxies....many supernova probably have taken place producing the heavier elements, that are then recycled...Our Sun is such a Star, said to be 3rd Generation....totally reasonable, I would think for such a Star Factory situation.
Of course, we need to remember that even metal rich galaxies and star forming regions don't have much besides hydrogen and helium. And that our third-generation Sun is made up of over 98% hydrogen and helium by mass, and 99.9% hydrogen and helium by number of atoms.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

SouthEastAsia

Re: APOD: Recycling NGC 5291 (2015 Nov 21)

Post by SouthEastAsia » Sat Nov 21, 2015 10:54 pm

My question would be:

Are these dwarf galaxies which are being flung out into intergalatic space expected to be gravitationally pulled back into a joined galaxy eventually? Or is there sufficient escape velocity where they can be ejected out into intergalactic space and endure individually as a cluster? Thanks in advance.

User avatar
neufer
Vacationer at Tralfamadore
Posts: 15967
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Recycling NGC 5291 (2015 Nov 21)

Post by neufer » Sun Nov 22, 2015 1:51 am

SouthEastAsia wrote:My question would be:

Are these dwarf galaxies which are being flung out into intergalatic space expected to be gravitationally pulled back into a joined galaxy eventually? Or is there sufficient escape velocity where they can be ejected out into intergalactic space and endure individually as a cluster?
The APOD states that "the dwarf galaxies were likely born in intergalactic space."

They are orphans and are likely to remain so. (Unless a Snow White galaxy happens by.)
Art Neuendorffer

SouthEastAsia

Re: APOD: Recycling NGC 5291 (2015 Nov 21)

Post by SouthEastAsia » Mon Nov 23, 2015 7:32 am

neufer wrote:
SouthEastAsia wrote:My question would be:

Are these dwarf galaxies which are being flung out into intergalatic space expected to be gravitationally pulled back into a joined galaxy eventually? Or is there sufficient escape velocity where they can be ejected out into intergalactic space and endure individually as a cluster?
The APOD states that "the dwarf galaxies were likely born in intergalactic space."

They are orphans and are likely to remain so. (Unless a Snow White galaxy happens by.)
Interesting. So are there other examples of similar dwarf galaxies (ejected from a galactic collision), drifting in intergalactic space without any inter-gravitational forces pulling them either way?

User avatar
Ann
4725 Å
Posts: 9516
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Recycling NGC 5291 (2015 Nov 21)

Post by Ann » Mon Nov 23, 2015 7:52 am

SouthEastAsia wrote:
Interesting. So are there other examples of similar dwarf galaxies (ejected from a galactic collision), drifting in intergalactic space without any inter-gravitational forces pulling them either way?
The Tadpole Galaxy.
Hubble Legacy Archive, ESA, NASA, Processing: Bill Snyder

Check out the caption for the APOD. You will find a link to the galaxy at left, the Tadpole galaxy. You can see bright bluish clumps in the galaxy's long tidal tail. The bluish clumps are dwarf galaxies in the making.

Note that these dwarf galaxies have not been ejected from a larger galaxy, but they are forming out of the material in the tail that was ejected from the large galaxy.

Ann
Color Commentator

starsurfer
Stellar Cartographer
Posts: 3528
Joined: Thu Mar 15, 2012 7:25 pm

Re: APOD: Recycling NGC 5291 (2015 Nov 21)

Post by starsurfer » Mon Nov 23, 2015 7:45 pm

This is a wonderful image of a beautifully peculiar galaxy! The length of the tidal tails/dwarf galaxies is astounding, the universe never ceases to astonish me! What an age we live in when amateur astronomers can set up a southern remote observatory in the mountains of Chile! For those of you wondering, the Seashell Galaxy is the smaller galaxy below the central one with the dust lane. It is more formally catalogued as NGC 5291B and MCG-05-33-005. An image by CEDIC of most of Abell 3574 can be seen here. The centrally dominant galaxy IC 4329 is also interesting as it is a shell elliptical galaxy.

SouthEastAsia

Re: APOD: Recycling NGC 5291 (2015 Nov 21)

Post by SouthEastAsia » Thu Nov 26, 2015 12:06 am

Thanks Ann for your interesting reply, but I guess my question again would be...

Do these common 'dwarf galaxies' have sufficient escape velocity to drift out into inter-galactic space, indefinitely? Or will they more likely be gravitationally pulled back into some repetitive 'dwarf-parent' collision within the next couple hundre million years give or take?? Thanks in advance!

User avatar
Ann
4725 Å
Posts: 9516
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Recycling NGC 5291 (2015 Nov 21)

Post by Ann » Thu Nov 26, 2015 2:31 am

SouthEastAsia wrote:Thanks Ann for your interesting reply, but I guess my question again would be...

Do these common 'dwarf galaxies' have sufficient escape velocity to drift out into inter-galactic space, indefinitely? Or will they more likely be gravitationally pulled back into some repetitive 'dwarf-parent' collision within the next couple hundre million years give or take?? Thanks in advance!
I'm not the best person to ask about this. You should ask Chris.

However, I think the question of dwarf galaxies formed in a tidal tail of a large galaxy can be compared with the situation in the solar system. What are the chances that an object that has formed inside the solar system will drift away from the solar system? I would be surprised if it can't happen. In fact, it seems to me that objects in the Oort Cloud, which are at the limit of the Sun's gravity well, really should drift away now and then.

But in general, I think that objects inside the solar system rarely drift away out of the Sun's "sphere of influence" altogether. So my guess is that the dwarf galaxies that have formed in the vicinity of the Tadpole Galaxy will stay in the vicinity of the Tadpole Galaxy. (Chris, or Neufer, might disagree.)

When it comes to the dwarf galaxies that have formed out of the gas tail of NGC 5291, we must remember that NGC 5291 is part of a moderately large galaxy cluster. Chances are that the dwarf galaxies will stay inside the galaxy cluster, even if they should drift away from NGC 5291 proper.

On the other hand, a galaxy cluster is likely to be a gravitational pin ball machine on a cosmic scale. It is a known fact that lightweight stars are likely to be ejected out of the massive stellar conglomerates known as globular clusters. Then again, a star is very different from a galaxy. Stars, especially small stars, are very compact objects that are very difficult to break up. Stars considerably less massive than the Sun are almost impossible to break up, if they don't suffer calamities comparable to being captured in a shrinking orbit around a black hole.

Galaxies, by contrast, are fluffy. It could well be that the dwarf galaxies that form out of galactic tidal tails will eventually "leak stars every which way" to the point that they can no longer be thought of as galaxies.

Ann
Color Commentator

User avatar
Chris Peterson
Abominable Snowman
Posts: 14354
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Recycling NGC 5291 (2015 Nov 21)

Post by Chris Peterson » Fri Nov 27, 2015 8:39 pm

tarzan wrote:For the umpteenth time, APOD, galaxies CANNOT "collide." It's really horrifying that you insist on making the same error over and over.
And for the umpteenth time plus one, galaxies can and do collide, resulting in material interactions that release energy and stimulate new star formation, as well as ejecting material into intergalactic space.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com