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RING GALAXIES THREAD


Mike JW
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This thread is for adding in your observations of RING GALAXIES.

Here is my somewhat basic understanding of ring galaxies.

Ring Galaxies – a galaxy with a ring (torus like structure) of stars. If only it was that simple. There seems to be various ways that a ring may form. About 50% of spirals have rings or partial rings and are most common in barred galaxies. The bar of stars sets up some sort of resonance pattern in the orbiting stars.

Three principle current theories of ring formation.

If the galaxy has a bar that becomes unstable as the galaxy rotates then the stars in the bar are migrated outwards to form a ring structure. (this is my simple version – dark matter and Byronic pressure are involved……)

Galaxy collisions such as in Arp 147 can result in a ring. If a galaxy passes straight through another galaxy then a ring is likely to form. A slanting blow, near misses are less likely to form a ring. As the smaller galaxy plunges into the bigger one, pressure wave ripple outwards (radially propagating density waves to be precise) collecting up the gas and compressing it at the same time and initiating star formation in a ring.

The third mechanism is where there is the formation of a very large spiral from the surrounding intergalactic medium. As material flows inwards and if conditions are right, rings of hot blue stars are formed rather than spiral arms.

The above is good enough for me. There are many technical articles out there for those who like the in-depth detail. Today I discovered an article suggesting that way back near the start of things there were magnetic wormholes and I quote

‘hypothesis that at least some of such rings could be remnants of relic magnetic wormholes. It turns out that magnetic wormholes may directly collect ring clumps of baryons in a process which is not based on the development of perturbations in dark matter component This means that the dark matter halo in such structures may have peculiar features, different from those observed in galaxies, In particular, in the case of wormholes the dark matter halo can be almost absent. This argument however does not work, if dark matter phenomenon has a pure topological origin, or it appears due to some extension of general relativity. The only stringent feature of such objects is the presence of a large-scale toroidal magnetic field. In the rest, the final form of the ring galaxy formed by a wormhole does not differ from that predicted by standard mechanisms. Indeed, upon the recombination epoch in the case when the wormhole collapses the ring may contain a more dense and old collection of stars (a small galaxy) in the center of the ring (as in the case of the Hoag’s object), or, when the wormhole expands further, the center part of the ring may remain empty.

See the link https://link.springer.com/article/10.1140/epjc/s10052-020-8395-7

This link is at about my level with a nice simple video: https://www.syfy.com/syfywire/one-ring-galaxy-to-bring-them-all-and-in-the-darkness-bind-them

This link https://medium.com/swlh/giant-ring-galaxy-existed-in-the-young-universe-ad65899126cd gives exciting info on the oldest collisional ring galaxy to be discovered - R5519 at about 10.8 billion years ago.

Ring Galaxy classification gets complicated.

An ‘r’ in the notation indicates a ring – no surprises there then!

(R) at the start indicates an outside ring, (RR) indicates two outside rings and (R’) indicates an outside pseudoring. A pseudo ring looks like a ring but isn’t. (r) indicates an internal ring.

However, rings can become lenses (‘L’ for outer or’ l’ for inner). I think rings evolve into lenses but I cannot find a simple definition of a lense. I am not even sure I could recognise a galaxy lense despite looking at various illustrations. My best guess is a ring is a well-defined structure and a lense is wider and fuzzy in appearance.

Now for the final complication, there are nuclear rings – these tend to be tight and bright around the nucleus, with the ‘n’ notation.

https://ned.ipac.caltech.edu/level5/Sept11/Buta/Buta6.html - will take you to more info on rings

try these for some light reading!!!!!! https://arxiv.org/pdf/1906.08124.pdf  https://arxiv.org/pdf/1501.00454.pdf  https://arxiv.org/pdf/1707.06589.pdf

I hope the above has got you excited to go out there and spot a ring or two.

PS – if you have any other info or spot mistakes in the above let me know and I can add it in/change things.

Have fun observing,

Mike

A list of ring galaxies to get us started.

Ring Galaxy.xlsx

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Posted (edited)

First up is an old friend, Arp 148 in UMa. Not the easiest of targets  to view. Its to the right of centre in the wide shot. It is a classic example of a galaxy doing a direct hit on another one. This pair are known as Mayall's object and lie about 500 million lyrs away. The offending galaxy has gone through the centre and is now heading out the other side. The shock wave creating the ring. Search out Hubble's image for this pair.

50810940_Arp14815Mar21_09_35_47.png.f3dd2824cca39bbda796f3bf7a967fc8.png484926767_Arp14815Mar21_09_37_17.png.0c5d8d077999a719eb94a1aed3e42718.png

 

 Arp  336  in UMa - NGC 2685 takes us to the nightmare of galaxy designations - it is (R) SBO^ / pec (Sy 2) = outside ring, barred lenticular, messed up and very active nucleus (I do not know what the ^ stands for - any suggestions?). It is  an example of a Polar Ring (ring goes around the poles rather than around the ecliptic). It is also called the Helix galaxy. Two galaxies have collided causing one to wind around the other and creating a large ring of stars. The spindle in the middle is more or less a normal SO galaxy and in my shot you can get hints of the spiral pattern (helix) of the second one which has wound around the central  galaxy. There are some beautiful images on the web.

Seyfert 2 galaxies - black hole doing its thing at the centre with a bright nucleus (visual) and bright in the infrared, indicating much dust/gas.

1788788181_NGC268515Mar21_13_48_52.png.d7f73762a3501dc8e55e9141558cc14e.png.

UGC 6309 in UMA  is a lovely sight and is classified as SBc - barred spiral with arms not too tight but personally when I compare to standard galaxy pictures it looks more like SBb. Then there is the small matter of the ring or is it? I cannot find any official ring classification so I am suggesting it should be (R')SBb - pseudoring barred spiral..........

 

668658918_UGC630915Mar21_14_41_47.png.410f62ffcaf2ab80b299e7b3c0e87218.png970848898_UGC630915Mar21_14_44_32.png.4d2ae14b6de072e1f71e385dba4d2c81.png

 PGC 38265 in UMa  is tiny and faint. I have distance data and nothing else. It lies 745 million lyrs away. Many of the fuzz spots in the left hand shot are in fact mag 18/19 galaxies.

46923418_PGC3826515Mar21_14_50_05.png.d04a7c5b1c5d77b65dfba12978041baf.png532201853_PGC3826515Mar21_15_06_09.png.d01507d2e92f05bdfd93428e85cc6e2b.png

 

Mike

 

 

 

 

Edited by Mike JW
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Some really remarkable galaxies there. UGC 6309 is so unusual -- very hard to get my head around that. I can't find what the ^ means and I have trawled through the entire N page table in the most recent galaxy classification I could find...You've really been able to pull a lot of detail out of Arp 336, with the helter-skelter trails and the bomb-shaped outer envelope -- wonderful shot. The 3 Arp ring galaxies I think I have visited (146-148). I'm looking forward to both observing some of these and seeing what other shots get posted in this thread.

Martin

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Posted (edited)

Arp 224 (NGC 3921) in UMA. This is thought to be a merger in process - the close up shot gives a hint of of two nucleus in close proximity. It lies about 275 million lyrs away. It has a starburst nucleus which is really no surprise as these two galaxies collide. Designation is (R') SA (s)O / pec. The R' indicating a pseudo ring - in however many millions of years it might well become a proper ring.

The Zwicky cluster - ZWCl 1148.6+5523 is centred on NGC 3921 and the various fuzz spots are galaxies at about 1 billion lyrs away. Down and to the left on the wider shot is another ZWCl (only the cluster edge in view) where the galaxies are a touch nearer at about 800 million lyrs away.

950184047_NGC392115Mar21_14_33_43.png.23afd9be451258409fb670d97ee76a93.png1863615836_NGC392115Mar21_14_34_13.png.386d029fa4400ee6a9dcbd3b9fe0a8f4.png

 

UGC 5055 (Markarian 114) in UMa.  One of those WOW moments as this galaxy appeared in the middle of its guardian stars . Designation (R') SBb (Sbrst) - not a true ring galaxy, just the appearance of one with those spiral arms turning back on themselves. 363 million lyrs away.

243081823_Markarian11415Mar21_14_16_41.png.17d8d379eae8b546f156b580c2c93fbb.png1366245980_Markarian11415Mar21_14_18_30.png.9a8de6ad1137cb9baa4d5db115b471bb.png

UGC  6334  in UMA.  This is a nice example of  a lenticular with no bar and an outside ring - hence (R) SO/a - now what does this mean? SO = lenticular where not sure if it has a bar or not (SAO=unbarred, SBO =barred), so I am assuming the /a might be indicating the preference for it lacking a bar?

868207527_UGC633415Mar21_15_15_56.png.deef4e9827a936a01c13e2f57d9be1b1.png878450620_UGC633415Mar21_15_16_22.png.f5676e2da2d06538b3c7de29fdd43120.png

PGC 31214 in UMa, is in the ring galaxy list as (R) Sab at a mere 919 million lyrs away! I was using the C11 for this shot so it was hard to pick up at mag 16.

614936306_PGC3121417Mar21_07_51_00.png.6595d186d7d1f80fd4fc66fd7208bf70.png

Arp 143 in Lynx is a glorious mess, made up of NGC 2444  - SO (Ring A), merging with NGC 2445 - Im (pec) (Ring B). So we have a lenticular merging with Magellanic type dwarf, irregular galaxy. Along with the mess we get star forming regions in 2445 and two rings for the price of one.

1671119879_Arp14315Mar21_09_50_59.png.6bf19c40274f9618ca96c2b853157a41.png

 

NGC 3945 is found in UMA. I was thrilled to see this one pop onto the screen. This is bigger than the Milky Way at about 120,000 lyrs diameter and 68 million lyrs away.

It is a 'Saturn' look a like. My first thought was just how many rings have we here?  - (R) SBO^ + (rs) + LINER

1964106854_NGC394515Mar21_13_59_06.png.2bf8ae162728fa229f346751c364da25.png

NGC 3945 in Bootes is SB(rs)ab - LINER. rs = spiral arms coming off the end of the bar and forming a ring, which my shot picked up. There is the extra halo fuzz but this is too diffuse to be considered a ring?

1283528513_NGC594515Mar21_15_21_38.png.6570fcfe67aa12a32350b93e040dadea.png

As always it is worth the cold, wrecked sleep patterns.... to 'see' such sights.

Mike

 

 

Edited by Mike JW
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Fascinating objects. I can add Arps 145 and 146, plus my take on Arp 148. These come from the last few years.

Ignore some of the labelling of seeing etc; these come from a rogue version of Jocular.

Arp 145 consists of a very clear doughnut ring (PGC 9060; type S0), and the ingressor (?) UGC 1840, type S0-a. The interesting thing about these, observationally, is the presence of several foreground stars and the possibility that the fuzzier 'star-like' things are knots or a galactic nucleus in the case of the spherical object. The ring itself is not uniform, seemingly mottled in its Northern sector.

There is an intriguing tack-shaped vertically-oriented bit of fuzz just to the NW too. 

I probably mentioned before that I have a great fondness for this field as it is the one I used when testing the live stacking alignment algorithm. I couldn't get it to work for ages until I worked out I had the x and y coordinates reversed...

941477685_Arp14521Mar21_14_11_13.jpg.9a4a24f7a698bfcacf4730894bbf420d.jpg

 

Arp 146 in Cetus is a tiny smoke ring, about a third of the apparent size of Arp 145 but similar in many respects, including the non-uniform ring presumably left by the passage of the other galaxy. This is 1.1 billion light years away while Arp 145 is about 262 million LYs distant, so the actual sizes of these collisional pairs must be quite similar. Further away still is a z=2.1 redshift quasar which at mag 19.0 is quite bright.

1768098742_Arp14621Mar21_14_08_26.jpg.13acd6a67be567f1d0a1b21e54e8b62f.jpg

 

Finally, here is my take on Arp 148 -- certainly nothing added relative to Mike's as far as the ring pair is concerned but always fascinating to see the torpedo-like ingressor. Interestingly, these must be of a similar actual size as the earlier two Arps given the apparent size/distance=500 MLyrs relationship. All I can add are a couple of very distant quasars. The z=3.0 one corresponds to a light travel time of 9.5-11.5 billion years according to my 'go to' redshift calculator: http://astro.ucla.edu/~wright/CosmoCalc.html

1262702818_Arp14821Mar21_14_06_08.jpg.f74155aea20dc6e3797aa95e43e0ccaf.jpg

 

cheers

Martin

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Thanks Martin for adding in the Arps. I have checked my Arp 145 but it does not add any extra detail. Always a mystery how you get those extra spider spikes in this shot but I do rather like them - adds to the drama.

Mike

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Ah, those deliberate extra spikes... I have a misaligned secondary and this being EEVA I haven't done anything about it in the last 6.5 years since I bought the Quattro. That accounts for one set. I've no idea where the others come from. I would say they are second harmonics of the first set somehow. Perhaps it is time to disassemble everything and clean the mirror at the same time.

Martin

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  • 1 month later...

                                                                                         I have been going through my Ring Galaxy observations in Leo.

NGC 3821 is a lovely example of an outer ring - (R)SAB (s)ab                                             NGC 3646 is a beautiful  spiral galaxy to view, with star forming regions  - SA (r)bc pec

I have also seen this galaxy classified as SO. Off to the right is PGC 36293 - what a           The internal ring is partially hidden by a spiral arm from our perspective

lovely barred spiral, SABb

918188070_NGC382115Apr21_18_24_07.png.fb78ff3435c2e97f2b3e873dd7470505.png512570054_NGC364615Apr21_18_24_49.png.5a5ca627534ccecd0a36443bd362b542.png

Mike

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Just checked my observations and I don't have either of those listed, but they're both real beauties. The 'far' arm in NGC 3646 appears to be rippled. It just shows that nearly every galaxy has something new and distinct to offer (except for most of the ellipticals 😉)

NGC 3821 is a great example of a ring, almost perfectly face on. And the galaxy partly obscured by the star to its right makes for an interesting field.

I hope I'll get a chance to look at these with the moon out of the way. 

Thanks for posting

Martin

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  • 1 month later...

June 1st 2021 - there was me pottering about in Serpens and looking at my lists I saw this bright galaxy - NGC 5921 (mag 10).

What a surprise when this ring galaxy appeared on the screen. Classified as SB(r)bc LINER (= bright nucleus). It lies 79 million lyrs away, has a strong bar and a slightly elliptical bulge. The two spiral arms have many H11 regions (I picked up a few of them). This inner ring galaxy was not even on my list of ring galaxies.

 

1321871104_NGC592102Jun21_18_17_40.png.6f9429d1d76f2fdc0cd71c1e57e663da.png

Mike

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Lovely shot. I just looked this one up in the de Vaucouleurs atlas where it figures as a luminosity class I-II standard for Sb galaxies. The image shows an extensive and quite messy set of spiral arms extending 3-4 times the width of the central 'theta' part in your shot. I imagine this is one of those galaxies that just gets progressively more detailed with increasing overall exposure.

Martin

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I probably should go back to this one and run the camera for longer. I did actually run it for about 5 minutes and then deleted the poor subs (the unsteady ones). As usual, so much to see..

Mike

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Those extra spikes are due to things like mirror clips. The hints are how many, the orientation compared to the secondary vanes and whether any are masked by projections like the focuser tube. 

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