Hula Hoop Galaxy

[Ken Crawford]

Hello,

We now know that an important part of galaxy formation is the fact that many larger galaxies tear apart and absorb smaller galaxies called Dwarfs. During the merger process, the dwarf galaxy orbits around and sometimes through the main galaxy, leaving a trail of debris around the larger galaxy. Because this galaxy is about 55 Mpc (179 million light years) we are lucky enough to see the possible tidal star streams. They appear like a hula hoop around the core of the main galaxy. These loops are very well defined and are thought to be at least two orbits of a dwarf galaxy.

This target is getting to the limits of my imaging system but you can just start to make out a faint dust lane around the core.

Click to zoom and pan and don't forget the full screen button.

http://www.imagingdeepsky.com/Galaxies/NGC7711/NGC7711.htm

Thanks for taking the time to look . . .

Kindest Regards,

[Alchemy]

Interesting image, always nice to see the unusual and different, the negative really shows the tidal movement well.

[bokglob]

:eyepop: Thats a background fuzzy with background fuzzies! Incredible, 179 million years back and thats close in the scheme of things! Intergalactic perspective makes my brain hurt:confused2: Thanks for the buzz!

[John Hothersall]

Thats an interesting structure that a big scope can really show well, great colours for such a far off galaxy.

John.

[Lester]

Wonderful view, and one I have not seen before. Thanks Ken. All the best.

[Ross G]

Thanks Ken,

An amazing photo of a new object for me.



Ross.

[Ken Crawford]

Thanks for the kind words, I know this is not a grand galaxy but it is interesting to look back in time at the morphology of it.

Kindest Regards,

[lebowski]

very interesting structure.
Ciao Ken

[SkyViking]

That's very nice and an interesting view of the structure in the negative image, it really shows well. It reminds me of the 'Atoms for Peace' galaxy.

[strongmanmike]

Quite a bit to see considering its distance Ken, would normally be little more than an elongeted smudge so a great capture there really :thumbsup:

Mike

[gregbradley]

Awesome Ken.

You caught those faint tidal streams very brightly.

How are you finding the U16M compared to the U09000?

Greg.

[Ken Crawford]

Thanks Greg,

I am finding there is more information that is useful for decon (you need good sampling) so I was able to be recover this thin and faint dust lane because of it. But I do miss the sensitity of the u9000 larger pixels as it does do deeper faster. So I am finding I need to image about 20 - 25% longer to get the same S/N.

The great thing is that both cameras have the same body style so in the winter when the seeing is not quite as good for me, I can throw the u9000 on my 10 slot filter wheel with just a few bolts. It is very easy to swap cameras now based on what I am imaging and the seeing conditions.

Regards,

[gregbradley]

Interesting Ken. Well you've got the best of both worlds there.

Greg.

[madbadgalaxyman]

That's one strange galaxy, Ken.

This galaxy, overall, seems asymmetric and disturbed, and not to be in a settled state. (the overall asymmetry is far in excess of what is normal for mildly disturbed galaxies)

I can't recall seeing anything like this morphology, though I am familiar with the morphologies of a large fraction of the NGC/IC galaxies.

I'll have to "cogitate" about this one, and also consult the literature.

[Ken Crawford]

Thanks! If you wish to read a bit about this galaxy and it's streams, here is the paper from a steam hunting team. They are using the SDSS data to detect them. I have shot two of there detections so far. I sent them my results and they were pretty impressed as they are doing follow-up with a 2.2 meter system and I am just about as deep. They are just about ready to release a paper with many more detects (lots of new targets coming!)

http://arxiv.org/PS_cache/arxiv/pdf/1102/1102.2905v1.pdf

Regards,

[renormalised]

Could be a case of our angle of view onto this object, or, it's taken a hit from something else that we haven't yet identified at some time in the past. Also, another reason...how big was the interacting galaxy that produced the "hula hoop" star streams and the rest of the debris around this galaxy?? It may have been bigger than we suspect. What was the geometry of the collision etc etc.

How many papers have been published about this galaxy and/or similar galaxies and their morphologies??.

BTW, Ken....nice piccie:):)

[Ken Crawford]

It was most likely a dwarf galaxy and it is believed to have made at least 2 orbits. There are several N-Body simulations that show how these interactions work. Our Star Stream team has several that were done. These are some that are currently being studied . . . .

Here is another stream that I have captured but with only one "loop" but a simular type orbit. It's stream is much fainter and harder to capture.

http://www.imagingdeepsky.com/Galaxies/NGC4684/NGC4684.htm

http://www.imagingdeepsky.com/Streams.html

Kindest Regards,

[madbadgalaxyman]

Thank you, Ken, for the link to the paper.
This is a tough object, and you have done an excellent job on it.

This paper is an excellent compilation of deep images of various galaxies.....and it could be useful for testing the ability of imagers to reach very deep in their astronomical images.
"Image deeper, sharper, or wider, and you are sure to turn up something new"

I didn't find much about this galaxy in the astronomical papers archive at http://adsabs.harvard.edu (http://adsabs.harvard.edu/) , so it has had little attention from professional astronomers, to date.
S.M. Kent provided some data about this galaxy in the 1984 ApJS, and Googling on this galaxy will find some NIR and Optical imaging data by Peletier and Balcells.

For comparison purposes, I attach the g+r+i bands composite image from SDSS (downloaded from Skyserver DR8) :

100527

This galaxy is nominally an S0 or Very Early Sa galaxy, though it deserves to be said that the S0 morphological class is a "broad church" which encompasses galaxies with giant bulges and minimal disks as well as objects which are more similar to spiral galaxies but without most of the usual ISM and star formation. (A lot of galaxies which are "not quite S0" and "not quite Sa" end up in the S0-a (S0/a) class, which is absolutely the rubbish bin of the Hubble Sequence, as it is negatively defined)
But traditional Hubble classification methods classify only the structure of a 2-D image, and sometimes tell us little about the underlying three-dimensional galactic morphology.

The surface brightness of this galaxy is very modest indeed, judged from the faintness of this galaxy in DSS images. Perhaps the highest contrast of the DSS images of it is at:

http://server1.wikisky.org (http://server1.wikisky.org/)
(while not the sharpest DSS images, these seem to be at higher contrast than usual)

See also the color composite image at Aladin, which is my favourite version of DSS:

http://aladin.u-strasbg.fr/AladinPreview

I do agree with our mutual friend "renormalised" that the perturbation of this galaxy looks like it could have originated with a perturbing object of significant mass.

The degree of asymmetry or lopsidedness in the apparent (two-dimensional) distribution of the stellar light is remarkably high. The observed morphology is indeed quite singular,at least if we compare the observed morphology to examples of disk galaxies that are not an immediate product of a major merger between two galaxies.
This is not one of those galaxies in which there is a large apparent optical asymmetry caused by OB stars and HII Regions without there being a corresponding asymmetry in the underlying mass-dominant Old Stellar Population which is better traced in the NIR regime. (Unfortunately the NIR image from the 2MASS survey is too faint to show anything meaningful about this galaxy.)

There is little star formation apparent in this galaxy, judging from the lack of FUV emission detected in the GALEX image of it. Its B-V optical color (within the effective aperture) of 1.03 (in Prugniel and Heraudeau's catalog of aperture photometry) is redder than that of any normal spiral galaxy, and in fact this color value is similar to the optical color of an elliptical galaxy!

This low apparent Star Formation Rate and red optical color strengthens the case for this galaxy being classified as an S0.
However, the morph. is so peculiar, that perhaps an orthodox Hubble type is not applicable.

[Stevec35]

I think I already commented on this on another forum but excellent work as always Ken.

Cheers

Steve

[marco]

Nice image Ken of what I believe to be a very faint object. It looks like somebody chopped away the right arms of a spiral galaxy :) Thanks for sharing!

Clear Skies
Marco