Object of the Week, April 19, 2020 - The Galaxy Chain NGC 2633/2634/2634A and the surrounding IFN

[Uwe Glahn]

NGC 2633 (Arp 80, VV 519, UGC 4574)
R.A.: 08h48m04.6s Dec.: +74°05'57"
Magnitude: 12.0 vmag; SB 13.2 mag/arcsec²

NGC 2634 (UGC 4581)
R.A.: 08h48m25.5s Dec.: +73°58'02"
Magnitude: 11.8 vmag; SB 13.0 mag/arcsec²

NGC 2634A (UGC 4585)
R.A.: 08h48m38.1s Dec.: +73°56'19"
Magnitude: 13.5 vmag; SB 13.0 mag/arcsec²

I first came across the field because of the astonishing picture of Peter with a 5-inch Apo. It shows the nice Galaxy Chain NGC 2633/2634/2634A behind faint IFN nebula. The question for me was - are the faint nebula visible and how does the Chain look like?

But let's start at the beginning. Both brighter NGC were discovered by Wilhelm Tempel in 1882 with his 11-inch refractor at Arcetri Observatory, Florence. As often not without some discrepancy. The "lost/not found" NGC 2630/2631 are suspected to be a double observation of NGC 2634/2634A.
Physically, both, or all three galaxies lies around 100 MLj but seems to show no gravitational bounding as tidal tails or peculiar morphology.
NGC 2633 is cataloged as Arp 80 and shows a bright bar with two brighter and wide wounded arms. The galaxy belongs to the group of starburst galaxies. Pictures show structured arms.
NGC 2634 itself shows faint shells which are recent discoveries from 2000 [2000AAS...196.2909K].

But now to my questions. First to the chain. After observing and sketching NGC 2633 a few years ago, lower magnifications shows all three galaxies with direct vision. Averted vision shows a fourth galaxy between NGC 2633 and NGC 2634. In a row of 12' length the chain is a beauty. All four shows different morphology. Although low magnification the spiral structure of NGC 2633 is clearly visible and the shell structure of NGC 2634 is clearly indicated.
But what about the faint IFN (Integrated Flux Nebula) in front of the chain? To my big surprise most of the structures are definitely visible without bigger problems. The main parts do easily fit into the searching eyepieces of normal (larger) telescopes. You don't need to have an extra short focal length like the amazing <f/3 telescopes of Mel Bartels. I unfortunately found no entry in SIMBAD as maybe Molecular Clouds or something.

picture: Peter, 5" Apo
link to astrobin
NGC2633_Peter.jpg

sketch: Uwe Glahn, 27", 113x, NELM 6m5+
link to the homepage
NGC2633_NGC2634.jpg

So its up to you to have a nice Galaxy Chain and perhaps the IFN in your telescope. So as always - give it a go and let us know

[Jimi Lowrey]

I have observed Arp 80 but I had no knowledge of the IFN near. I will try it soon and let you know what I see.

Thanks for the info on this Uwe cool field!

[hajuem]

Hi Uwe
Amazing observation Uwe !! Learn from this that you should watch over our "normal" objects !! The IFN nebulas seem to be and will be the current deep sky challenge. However, you need the right instrument for such observations and a lot of experience in visual observation. Cool presentation and observation Uwe !!

[MelBartels]

Uwe's sketch is very inspiring. I decided to see for myself. Since Uwe saw such great detail close in, I thought I'd concentrate on the wider perspective. Here's my sketch from last night.
It is a complex area of galactic cirrus, mostly faint, but very pretty with the modest grouping of galaxies.
It is great to compare views from the other side of the planet, with different observing and sketching approaches.
Arp 80 IFN.jpg
Mel Bartels

[Ivan Maly]

What an interesting field. I only have an observation for Arp 80 (NGC 2633), from last year (20" F/5, SQM 21.0, good seeing):

"Arp 80, NGC 2633, Cam. 5.5 mm. N of the line between 2 m10 stars (SW-NE). [Sub-] threshold star E. Bright NS core or bar with a starlike center. CW arm from S end of bar, runs parallel to the core on E side, widely separated. Opposite arm is just a short enhanced segment on NW edge of the halo. The long arm points in the general direction of, but does not connect to an enhancement N of the bar, which is widely separated and forms a right triangle with the nucleus and the subthreshold (visible as a diffuse spot) star to the E."

[Robin]

Hi Uwe,

I observed this galaxy group earlier this week with my 12" Dobsonian at 49x - 275x magnification. Most detail within the galaxies was visible at 275x.
NGC 2633: I saw a stellar core and a bar. At both ends of the bar I saw some appendages, hints of the spiral arms.
NGC 2634: Round symmetric galaxy with a bright core. More diffuse away from the core.
NGC 2634A: Edge-on galaxy, a bit brighter at the center.

I did not see the galactic cirrus at any magnification chosen.

Please find attached my sketch.

Clear skies,

Robin

NGC2633etcRobin.jpg

[Steve Gottlieb]

NGC 2633 from last March through Jimi's 48-inch:

Excellent, fairly large, two-armed barred spiral! The central part of the galaxy consists of a very prominent bar oriented ~3:1 NNW-SSE, with a very bright core. A striking spiral arm is attached at the south end of the bar. It bends sharply clockwise and extends north, on the east side of bar, arcing gently with a length of ~1.5'. This arm has a well defined inner and outer edge and is separated from the bar by a dark gap. As the arm extends north it dims slightly, but at the northern end bends sharply west [1.0' N of center] and noticeably brightens in an elongated piece [consisting of multiple HII regions on images]. At the north end of the bar a second arm emerges towards the west and starts to curl south, but fades and dims, reaching no further south than the center of the bar.