The Bear's Paw Galaxy (Arp 6) and an ultra-thin neighbour (IC 2233)

[Martin Meredith]

These two objects lie around 17' apart in the central portion of Lynx. I've manually mosaiced a pair of images I took to show the configuration (lower part is mono...).

 

I've observed the Bear's Paw Galaxy (Arp 6, NGC 2537) before without really looking into what kind of object it is. It certainly looks like no other galaxy I've seen before. This time, after observing in luminance only for a while I decided to add a few subs in each of R G and B, something I rarely do with galaxies unless they seem to demand it. In this case it helps to see some of the blue star-forming regions that make up the many knots in this peculiar galaxy. I later learnt that it is a Blue Compact Dwarf galaxy, about a 1/10 of the size of our galaxy, lit up by hot massive young stars, typically less than 10 million years old. I read that it is because it is formed of star clusters such as these that the galaxy lacks a typical 'galactic' shape. This paper [1] describes bubbles of ionized gas in the lower part of the central section.

 

 

 

IC 2233 is classified as an ultra-thin type SBc galaxy (classifed as Sd in [2]). In my close-up there are lots of knots in both the central region and towards the lower part, which also shows a slight bend. N is up in this image.

 

 

The possibility that these very different looking galaxies are physically related has been raised. Paper [2] suggests that they are not linked, but is a good read as it covers both of these interesting objects and contains some much more detailed images than those I obtained, particularly of the ultra-thin galaxy in the H-alpha band (which I think would be worth collecting some subs in -- next time). In [2] it is argued that a star-bursting galaxy like Arp 6 will never evolve into a 'normal' galaxy like IC 2233.

An interesting part of the sky!

cheers

Martin

 

[1] https://arxiv.org/pdf/astro-ph/9903060.pdf
[2] https://arxiv.org/pdf/0709.4249.pdf
 

[Mike JW]

Martin, wonderful contrast in galaxy types. It makes for an interesting session when different types are observed. In some of my recent sessions I have tried to do a mix as well.

Dr Arp classified Arp 6 as a spiral with low surface brightness. Some folk have suggested that its shape is a result of a merger. The remnant being the obvious bright blob - top right. A merger would explain the bright knots of star formation. Great idea to do the colour to show these hot blue regions. Thanks too for the references.

I do like ultra thin galaxies - visually and EAA.

I was out there last night but way behind writing up/posting.

Mike

[Mike JW]

Here is my image from last night (1/3/20). PGC 23057 above it. mag 15.7 spiral (hint of being a spiral in my shot but more obvious in yours). Mike

[Bill S]

Yep! I too decided to look at the Bear's Paw and some thin and ring galaxies. Here's my effort on Arp 6.

 

I didn't look at IC2233 but I did look at IC610, and three other thin galaxies. I'm still following up the background information to these and may post them later. Also took the opportunity to look at two comets (C/2019 Y4 ATLAS and C/2018 N2 ASSASN). Neither were very spectacular but again I may post snapshots later.

Best regards

 

 

[Martin Meredith]

Mika and Bill, thanks for posting shots. Its great to compare FOV, resolution etc with our different setups.

Martin

[Mike JW]

Agree. You guys with your shorter focal length set ups give the wider fov which I enjoy.