Arp 143: A collisional ring galaxy

[Martin Meredith]

A few days back I was observing some of the 9 Arps in Lynx. Arp 143 was the most peculiar of anything I saw during this session, and indeed one of the weirdest things I've ever seen. Verontsov-Velaminov called it a blue nest of galaxies while Arp used the understated description 'material emanating from elliptical'. De Vaucouleurs regarded it as an irregular ring galaxy.  To me it looks like a small sack of frogspawn.

Arp 143 (NGC 2444) is apparently a collisional ring galaxy still in formation, where the typical spiral structure is replaced by a ring of knots caused by collision of a spiral galaxy with an early type galaxy [2]. This other galaxy may well be the compact companion NGC 2445 which sits immediately to the north. Paper [1] is a fascinating read on many levels (not least to read about the technology available for these kind of studies as recently as 1992 compared to the sensors we use nowadays). It contains a mass of very detailed information about the individual regions which would complement an EEVA-style observation of these structures. Although [2] is primarily a radio wavelength study, it is well worth a look as it contains more recent hi-res mono and colour optical wavelength images of the pair. There is a lot of interesting structure to tease out here for the observer armed with a camera (see also [3]). NGC 2445 has a number of blue regions, indicating hot young recently formed stars (< 10 million years). I'd like to return to take a colour shot of this one. 

My observation is 17 x 15s subs = 4m15 (ignore the estimate on the photo).

There is a mag 20.2 (B) quasar just above the very obvious curving plume arising from the upper galaxy which I haven't been able to capture, in case anyone fancies a challenge!

 

 

 

[1] http://articles.adsabs.harvard.edu/pdf/1992ApJ...385..491A
[2] https://arxiv.org/pdf/1407.7369.pdf
[3] https://arxiv.org/pdf/astro-ph/9709134.pdf

The other Lynx Arps are also well worth a look for the variety of structures to observe.

cheers

Martin

 

[Mike JW]

I remember this freaky galaxy from my visit last year. Pity I lost the image. Thanks for the info which I have summarised in my own Arp document for when I get to revisit this chaotic scene. I have started reading the articles - way beyond my knowledge but of interest. Ring galaxies are fascinating. Mike

[RobertI]

That is a weird looking object! Thanks for the detailed references, very interesting. 

[Mike JW]

Morning Martin,

I took up your challenge last night. Transparency was excellent but the moon was bright. I too failed to pick up the mag 20 quasar but fun trying. Mag 20 I suspect is beyond the set up on a typical GB night but might be doable on the occasional excellent night. I might try the 15/camera. I wonder if the quasar is lost behind the fuzz of the galaxy plume. Mike

[Bill S]

I had a look at this last night too. I can see the frogspawn. It also looks a bit like a spotty bow tie.

 

Over five minutes of subs because I was looking things up while it was coming in.

[Martin Meredith]

In case useful to others, the lower shot from the DSS2 shows the position of the quasar (bright green square); the upper shot without the square suggests it is in the plume, but seems to be surrounded by a dark circle (perhaps not so much gas in the plume at this point). I think I can see that dark region in your image Mike.

 

 

[Mike JW]

Martin thanks for the image - very useful. Good to have confirmation that the Quasar is in the plume as we suspected.

Below is a very enlarged cropped image. The dark patch you refer to - seems to be there in my image.

The fun of this lark is it is making us study the area, the details in the image and of course the reading up - love it. 

Mike

 

[roelb]

back in Febr. 2018 I took this image with a ASI290MM on a Evolution 8" @ F/4.7 at Bortle 7

14 x 15 s