APOD: Arp 188 and the Tadpole's Tail (2012 Nov 08)

[ems57fcva]

As best I can tell, the small galaxy at the bottom of the photo IS the intruder galaxy. There is a bridge running between the cores of the two galaxies! It comes out of the central code at 6:00, sweeps up past the 2:00 position (where what I think is a tidal tail is being mistaken for the intruder), continues above Arp 188 and then dives down in front of Arp 188 towards a point to the right of the smaller galaxy. Then it turns like a "J" and heads into the core of the smaller galaxy.

My guess is that the smaller galaxy swept past Arp 188 going just above it to form a bridge between the galaxies. It then got swung around and down towards its current position. The tidal effects create the big tidal tail and a smaller one whose remnants at 2:00 are being mistaken for the intruder. The bridge then got stretched out and twisted around by the path the smaller galaxy took, but if you look for it, the full bridge is still there. In this case, the galaxies did not interact all that strongly and are now separating with their identities intact. The bridge is disintegrating as the galaxies continue to separate.

These bridges are something that I keep finding in cases of colliding galaxies, but I have never seen them modeled. There is something fundamental that we don't understand about interacting galaxies IMO.

[a.niwa]

You can confirm the intruder galaxy in the Hubble WEB site as follows,
http://hubblesite.org/gallery/tours/tour-tadpole/
Click play Movie > Click Distorted Shape > Click continue

[neufer]

You can confirm the intruder galaxy in the Hubble WEB site as follows,
http://hubblesite.org/gallery/tours/tour-tadpole/
Click play Movie > Click Distorted Shape > Click continue

==========================================================
[list]The Two Gentlemen of Verona Act 3, Scene 1[/list]
DUKE: Go, base intruder!
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[list]Titus Andronicus Act 2, Scene 3[/list]
TAMORA: Unmannerly intruder as thou Art![/color]
==========================================================

[BDanielMayfield]

The last expression in this apod's Explanation got my attention:

the Tadpole Galaxy will likely lose its tail as it grows older, the tail's star clusters forming smaller satellites of the large spiral galaxy.

I've always thought of galactic interactions as a canaballistic process where the number of galaxies always becomes less over time. It seems that that notion was too simplistic.

Bruce

[bactame]

This is an interesting pair of galaxies but the numbers used to characterize them is a problem. This apod, Mr Snyder and the Hubble link say that this pair of galaxies are approx. 400 million lt yrs away and that the two galaxies are approx 400 thousand lt yrs apart. Now i exaggerate a bit, the distance apart is cited as 300,000 lt yrs when mentioned.

However, we are looking at two likely disk galaxies, pancakes with a little syrup and butter in a short stack. If those two pancakes are 300,000 lt yrs apart then the galaxies themselves are gargantuan pancakes whose diameters are at least five times larger (using the cropped Snyder image on his website). 5 X 300,000 lt yrs = 1,500,000 lt years; which is a highly unlikely number for a galactic diameter.

So obviously this must be wrong for a galactic diameter anyway. What we see is a helix or rather a helical structure where the nearby galaxy nucleus is visible and the second hidden galaxy also has a hidden nucleus. What we see are the spiral arms separated by some smaller distance and the 300,000 lt yrs is a separation between galactic nuclei.

[Ann]

As best I can tell, the small galaxy at the bottom of the photo IS the intruder galaxy. There is a bridge running between the cores of the two galaxies! It comes out of the central code at 6:00, sweeps up past the 2:00 position (where what I think is a tidal tail is being mistaken for the intruder), continues above Arp 188 and then dives down in front of Arp 188 towards a point to the right of the smaller galaxy. Then it turns like a "J" and heads into the core of the smaller galaxy.

My guess is that the smaller galaxy swept past Arp 188 going just above it to form a bridge between the galaxies. It then got swung around and down towards its current position. The tidal effects create the big tidal tail and a smaller one whose remnants at 2:00 are being mistaken for the intruder. The bridge then got stretched out and twisted around by the path the smaller galaxy took, but if you look for it, the full bridge is still there. In this case, the galaxies did not interact all that strongly and are now separating with their identities intact. The bridge is disintegrating as the galaxies continue to separate.

These bridges are something that I keep finding in cases of colliding galaxies, but I have never seen them modeled. There is something fundamental that we don't understand about interacting galaxies IMO.

Personally I doubt that the small disk galaxy has anything to do with Arp 188. I believe, instead, that the disk galaxy near the bottom of the picture is a background object. It is very well-formed and bright, and its disk has symmetric dust lanes and star formation. Its appearance makes it resemble our large galactic neighbour, the Andromeda galaxy. Such well-formed and symmetric galaxies are almost always big, but if this galaxy is so close to Arp 188 that it has collided with it, then it must be small indeed. I find that extremely unlikely. Instead, I think that it is a big spiral galaxy that is many millions of light-years further away from us than Arp 188.

Also, if this galaxy had actually collided with a galaxy that was as big as itself or even bigger, then its symmetric shape would be completely ruined. This galaxy is simply much, much too well-formed to have had a recent close encounter with a galaxy larger than itself.

Indeed, when you take a close look at the "tail" that seems to emanate from the center of this spiral galaxy, it becomes obvious that the tail instead emanates from the small round galaxy at its lower right. The "tail" is in fact two long star streams emerging from opposite sides of the small galaxy.

But Arp 188 does indeed have a tail pointing downwards. Follow the tail down, and you'll come to a small round shape at the upper right of the small bright spiral galaxy. This small round object could indeed be a dwarf galaxy, a so-called dwarf spheroidal, that is interacting with Arp 188. This object and Arp 188 actually resemble the Andromeda galaxy and its dwarf spheroidal companion NGC 205.

Ann

[saturno2]

A Sideral Tadpole
The center of galaxy is very bright

[ems57fcva]

As best I can tell, the small galaxy at the bottom of the photo IS the intruder galaxy. There is a bridge running between the cores of the two galaxies! It comes out of the central code at 6:00, sweeps up past the 2:00 position (where what I think is a tidal tail is being mistaken for the intruder), continues above Arp 188 and then dives down in front of Arp 188 towards a point to the right of the smaller galaxy. Then it turns like a "J" and heads into the core of the smaller galaxy.

My guess is that the smaller galaxy swept past Arp 188 going just above it to form a bridge between the galaxies. It then got swung around and down towards its current position. The tidal effects create the big tidal tail and a smaller one whose remnants at 2:00 are being mistaken for the intruder. The bridge then got stretched out and twisted around by the path the smaller galaxy took, but if you look for it, the full bridge is still there. In this case, the galaxies did not interact all that strongly and are now separating with their identities intact. The bridge is disintegrating as the galaxies continue to separate.

These bridges are something that I keep finding in cases of colliding galaxies, but I have never seen them modeled. There is something fundamental that we don't understand about interacting galaxies IMO.

Personally I doubt that the small disk galaxy has anything to do with Arp 188. I believe, instead, that the disk galaxy near the bottom of the picture is a background object. It is very well-formed and bright, and its disk has symmetric dust lanes and star formation. Its appearance makes it resemble our large galactic neighbour, the Andromeda galaxy. Such well-formed and symmetric galaxies are almost always big, but if this galaxy is so close to Arp 188 that it has collided with it, then it must be small indeed. I find that extremely unlikely. Instead, I think that it is a big spiral galaxy that is many millions of light-years further away from us than Arp 188.

Also, if this galaxy had actually collided with a galaxy that was as big as itself or even bigger, then its symmetric shape would be completely ruined. This galaxy is simply much, much too well-formed to have had a recent close encounter with a galaxy larger than itself.

Indeed, when you take a close look at the "tail" that seems to emanate from the center of this spiral galaxy, it becomes obvious that the tail instead emanates from the small round galaxy at its lower right. The "tail" is in fact two long star streams emerging from opposite sides of the small galaxy.

But Arp 188 does indeed have a tail pointing downwards. Follow the tail down, and you'll come to a small round shape at the upper right of the small bright spiral galaxy. This small round object could indeed be a dwarf galaxy, a so-called dwarf spheroidal, that is interacting with Arp 188. This object and Arp 188 actually resemble the Andromeda galaxy and its dwarf spheroidal companion NGC 205.

Ann

Ann - You are mostly right. I was fooled by the star stream coming out of the background galaxy and getting mixed in with the tidal tail for the small galaxy that you mentioned. However, I now interpret that small galaxy as being the remains of the intruder, which has lost a lot of its material to the larger galaxy and the connecting bridge. Interpreting the overall picture gets a bit difficult for me now: The bridge and the secondary tidal tail are mixed together in this case. I am guessing that the intruder came in from below and behind, passed about the core of Arp188 and then swung down and ended up as the small galaxy that we are talking about. A lot of its original material ended up in the bridge, and is forming a new satellite galaxy that is being mistaken for the actual intruder. Close to the start of the bridge, a secondary tidal tail is also present, making the bridge look bigger than it really is. The extended period of interaction and its originally being much bigger would be how that small galaxy ended up creating the Tadpole Galaxy's tail.

The smaller galaxy is also worthy of comment. It has a small satellite galaxy just to its right, and what appears to be a star stream defining a closed path that goes from the core, through the satellite galaxy and the curves around behind the "parent" galaxy and back to the core.

[Roland]

I see a different story. The intruder galaxy is the one in the lower right. The trajectory path is as you say comming in from the foreground and above arp188, but then it traveled across and downward behind. I can see the haze trail leading to galaxy below. I can also see that the galaxy has been captured and is returning for another pass. It has a faint trail of haze showing its changing direction.

I think tadpole's tail formed because the intruder was aligned "edge on" as it was pulled into arp188. Since the intruder was being accelerated the receding side of the galaxy stars and dust were being flung backward as the rest of the intruder was pulled in.

[Chris Peterson]

I see a different story. The intruder galaxy is the one in the lower right. The trajectory path is as you say comming in from the foreground and above arp188, but then it traveled across and downward behind. I can see the haze trail leading to galaxy below. I can also see that the galaxy has been captured and is returning for another pass. It has a faint trail of haze showing its changing direction.

I think you are demonstrating more about how the mind works than about how galaxies work, given that it's doubtful any of these things can be determined visually from a single image. In actuality, most of what is known about the positions and movement of these bodies probably comes from Doppler shift data acquired with spectral studies.

[Roland]

I think you are demonstrating more about how the mind works than about how galaxies work, given that it's doubtful any of these things can be determined visually from a single image. In actuality, most of what is known about the positions and movement of these bodies probably comes from Doppler shift data acquired with spectral studies.

A working mind is a valuable commodity. I have no problem with you having a different point of view, although I'm not sure what it is with regard with arp188. My professional specialty deals with trajectories and forces, so I still trust my observation based on the single image. I prefer Ann's explaination.

If you wish to provide a link to the doppler shift spectral data I will be happy to revisit my conclusions.

[mike bischot]

It looks like the bottom right of this composite picture has a few frames that are the same. Can the editor confirm this?

[rstevenson]

It looks like the bottom right of this composite picture has a few frames that are the same. Can the editor confirm this?

This question was previously raised on Nov 8th, and answered too. Best to read the thread.

Rob

[Zapf]

I don't have any redshift data or whatnot, so I've only got my eyes to go with. The fainter tale that extends from Arp 188 to the center of the remote galaxy is a puzzle to me. Is it possible that distant galaxy is actually related to the faint second tail? Maybe that distant galaxy interacted with Arp 188 eons ago, leaving a long trail between them. Then, countless years later the second "intruder" galaxy showed up for Arp 188's second encounter?

[Zapf]

Please disregard my previous question. I do like Ann's reasoning, so I'll go with that. (That far galaxy in the lower right has excellent integrity.)