NGC 4250 is a ring galaxy - new discovery?

[gorann]

I recently posted an image of NGC 4236, which also contained the smaller NGC 4250. When I took a closer look at that galaxy I could discern a faint but clear outer ring. There seems to be very few images of this galaxy and I have not found any image showing this outer ring or pointing it out. I have here made a crop and a careful reprocessing to make sure that the ring was not an artifact of, for example, Gradient Exterminator or Hi Pass filtering, but it was clear that the ring was there also after only stretching the image.

According to this interesting article ringed galaxies are very rare, only one in 10 000 is of this category:
https://bigthink.com/starts-with-a-bang/ring-galaxies/

Since the original aim of this image was to look for a possible new PN, I was using a dual-band Ha+Oiii filter, which is not ideal for imaging galaxies as it blocks most of the visual light spectrum, but apparently the RASA 8 is enough of a light bucket to overcome this. Also, the galaxy is a bit on the small side for being imaged at a focal length of 400 mm, and this image is a drastic crop of the original.

Comments most welcome, especially those that prove me wrong!

Cheers, Göran

 

Here is my previous post where NGC4250 is that small galaxy in the top right corner:

 

Edited October 24, 2022 by gorann

[Shibby]

Interesting - definitely looks like a genuine ring. Whether it counts or not as a discovery, I've no idea?

I actually have rare, clear skies forecast tonight so I'll see if I can pick it up myself.

[symmetal]

I did notice this on your original image and thought it mught have been an artifact of star removal so didn't mention it. 🙂 The dark circle surrounding it doesn't appear on other images. It's just classed as a lenticular galaxy.

Alan

[Shibby]

Update: I can see it on http://www.sky-map.org/ (not very clearly, but it's there)

Edited October 24, 2022 by Shibby

[ONIKKINEN]

Very interesting indeed. Doesnt seem to be a popular subject as google comes up with just a handful of results with none of them mentioning it as a ringed galaxy.

Someone in decent skies with a big scope should be able to get a larger dimensioned image out of it since its almost 2 arcminutes. It seems to be very faint so a significant time investment under not great skies though. Almost tempted to give it a go but that would be yet another multi year project so maybe not 😬.

What classifies as a ringed galaxy, could it be an extended halo of sorts and not a flat ring? Hard to tell since it is face on.

[gorann]

5 hours ago, Shibby said:

Interesting - definitely looks like a genuine ring. Whether it counts or not as a discovery, I've no idea?

I actually have rare, clear skies forecast tonight so I'll see if I can pick it up myself.

Go for it! And thanks! It is raining here....

Edited October 24, 2022 by gorann

[gorann]

5 hours ago, symmetal said:

I did notice this on your original image and thought it mught have been an artifact of star removal so didn't mention it. 🙂 The dark circle surrounding it doesn't appear on other images. It's just classed as a lenticular galaxy.

Alan

 

4 hours ago, Shibby said:

Update: I can see it on http://www.sky-map.org/ (not very clearly, but it's there)

Thanks! Great that it not only me seeing it😁

[gorann]

2 hours ago, ONIKKINEN said:

Very interesting indeed. Doesnt seem to be a popular subject as google comes up with just a handful of results with none of them mentioning it as a ringed galaxy.

Someone in decent skies with a big scope should be able to get a larger dimensioned image out of it since its almost 2 arcminutes. It seems to be very faint so a significant time investment under not great skies though. Almost tempted to give it a go but that would be yet another multi year project so maybe not 😬.

What classifies as a ringed galaxy, could it be an extended halo of sorts and not a flat ring? Hard to tell since it is face on.

My guess is that to classify as a ringed galaxy it needs to have a clear separation between the centre and the outer ring.

[symmetal]

The galaxy is not face on to us, but the 'ring' appears to be which seems unusual. Some other small galaxies and bright stars are also surrounded by dark halos, suggesting the dark rings are artifacts so the brighter ring outside the dark ring may be an artifact too. 😉

If you post just the stack output and a simple stretch without any other processing it might settle the argument. 😊 

Alan

Edited October 24, 2022 by symmetal

[gorann]

39 minutes ago, symmetal said:

The galaxy is not face on to us, but the 'ring' appears to be which seems unusual. Some other small galaxies and bright stars are also surrounded by dark halos, suggesting the dark rings are artifacts so the brighter ring outside the dark ring may be an artifact too. 😉

If you post just the stack output and a simple stretch without any other processing it might settle the argument. 😊 

Alan

Wim just posted this confirmation on the post I made on Astrobin, so the ring seems to  be real and has been picked up by some scope:

https://www.oulu.fi/astronomy/S4G_PIPELINE4/quality5/decomp0042.html

But here is the tif if you want to try it:

20221019-20 NGC4236+DanaPN RASA1+2.tif

[tomato]

Apologies Goran, I only picked up on this thread after I set my imaging run away tonight on what looks like the first decent night in a while. 
It’s well placed for me for a while, so I’ll definitely train the dual Esprit 150/ASI178 galaxy rig on it, once I put it back together.
 

[tomato]

I’ve just checked the FOV using SGL/FLO’s astronomy tools, and I think there is a hint of it on the sky survey image.

[Martin Meredith]

Very interesting, and certainly looks like it has an outer ring (also in the SDSS image, though nowhere near as clear as yours), and it is rather odd that there is no (r) in its morphological classification. It seems possble to me that it has been overlooked.

BTW You might find some useful info on the fraught question of what defines a ring galaxy on this thread, as there are various types:

 

[wimvb]

DSS2 shows a hint of a partial ring in the red channel.

As the ring shows even with an NBZ filter, it shouldn't be too difficult to get a better image of it. The reason nobody has imaged the galaxy this way before is probably because it is small and not very interesting (apart from the ring). With a slower scope, it would take quite a few hours of integration time to reveal this feature.

 

Edited October 24, 2022 by wimvb

[symmetal]

There is a dark ring surrounding it, with a hint of a brighter ring outside on this simple heavy PS stretch, so I apologise for my scepticism Göran. 

My RASA 11 is all ready to go but there is cloud for the foreseeable future here so haven't been able to try it out. 😟

Alan

[mdstuart]

Fascinating. I observed ngc 4250 visually with my 16 inch scope in 2017.

Definitely looks like a ring galaxy in your image.

Maybe ask hubble or jwst to look at it!

Mark

[wimvb]

22 minutes ago, mdstuart said:

Fascinating. I observed ngc 4250 visually with my 16 inch scope in 2017.

Definitely looks like a ring galaxy in your image.

Maybe ask hubble or jwst to look at it!

Mark

Hubble already has (from the Hubble legacy archive):

How should we interpret this? The intensities don't seem to match.

Edited October 25, 2022 by wimvb

[tomato]

Interesting, the HST image doesn’t look much like it, the star near the centre in Goran’s and the sky survey images doesn’t appear to be there?

[gorann]

11 hours ago, tomato said:

I’ve just checked the FOV using SGL/FLO’s astronomy tools, and I think there is a hint of it on the sky survey image.

The best of luck Steve, I look forward to the result! It is faint so grab as many hours as possible.

[gorann]

3 hours ago, wimvb said:

Hubble already has (from the Hubble legacy archive):

How should we interpret this? The intensities don't seem to match.

Yes, that looks odd, what filters were used?

[gorann]

8 hours ago, symmetal said:

There is a dark ring surrounding it, with a hint of a brighter ring outside on this simple heavy PS stretch, so I apologise for my scepticism Göran. 

My RASA 11 is all ready to go but there is cloud for the foreseeable future here so haven't been able to try it out. 😟

Alan

Actually, I found that the "dark ring" is a visual illusion from the bright centre. I used the eyedropper tool in PS and measured the brightness in the dark ring and in the surrounding sky and they are the same.

[gorann]

11 hours ago, Martin Meredith said:

Very interesting, and certainly looks like it has an outer ring (also in the SDSS image, though nowhere near as clear as yours), and it is rather odd that there is no (r) in its morphological classification. It seems possble to me that it has been overlooked.

BTW You might find some useful info on the fraught question of what defines a ring galaxy on this thread, as there are various types:

 

Thanks Martin! I have now put a link to this thread on the Ringed Galaxies Thread.

[Shibby]

It looks to me like the outer ring might actually be the faint spiral arms. The overall appearance is a bit clearer in this Hubble image: https://hla.stsci.edu/cgi-bin/display?image=HST_11219_54_NIC_NIC2_total&izoom=1.000000&detector=NIC2&aperture=NIC2-FIX&title=11219_54 NIC2 detection (combined) UGC7329

(The one you posted, @wimvb, I *think* is through a UV filter)

Unfortunately I didn't manage to get out there last night to have a go at it myself.

Edited October 25, 2022 by Shibby

[gorann]

36 minutes ago, Shibby said:

It looks to me like the outer ring might actually be the faint spiral arms. The overall appearance is a bit clearer in this Hubble image: https://hla.stsci.edu/cgi-bin/display?image=HST_11219_54_NIC_NIC2_total&izoom=1.000000&detector=NIC2&aperture=NIC2-FIX&title=11219_54 NIC2 detection (combined) UGC7329

(The one you posted, @wimvb, I *think* is through a UV filter)

Unfortunately I didn't manage to get out there last night to have a go at it myself.

I stretched that Hubble image and it does look like a spiral galaxy. Apparently it is also annotated as UGC7329

[wimvb]

2 hours ago, tomato said:

Interesting, the HST image doesn’t look much like it, the star near the centre in Goran’s and the sky survey images doesn’t appear to be there?

 

1 hour ago, gorann said:

Yes, that looks odd, what filters were used?

I didn't have time to delve deeper into this. The HST image doesn't really match with Göran's image, at first glance, but this may be due to different filters being used. This is definitely going on the to do list, but not this side of New Year. The target is behind my obsy walls.