Keenan's System: a tidal stellar bridge

[Martin Meredith]

Last year I posted on a live observation of Arp 295, showing a tidal bridge of stars between two interacting galaxies. Tonight I had an unexpected opportunity (the forecast was wrong in my favour for once!) to look at a further stellar bridge in Ursa Major. This is known as Keenan's System (Arp 104). The two galaxies involved are NGC 5218 (top) and 5216. In addition to the bridge there are various counter-tails visible in each galaxy. There's a fairly recent description with images in this paper and also here.

This is the raw capture -- actually 25 x 30s subs -- which just about shows the bridge.

Inverting and auto white balance helps bring out the bridge at the expense of detail in the galaxies.

This was a fascinating system to watch emerge albeit on a cold night.

I've also marked in red a faint mag 19.6(V) quasar with a redshift of 3.12, corresponding to a distance of up to 11.6 billion light years. There are 3 other (closer) quasars in the image, unmarked.

Kit: 8" f/4 Newt + Lodestar X2 mono + Baader C filter mounted in alt-az, observed at the scope using StarlightLive.

cheers

Martin

[Helen]

Fascinating, thanks for sharing!

Helen

[elpajare]

Martin, this is a awesome picture.

Things like this make me love the video astronomy.

Thanks for sharing.

[niallk]

Amazing! 

[SilverAstro]

14 hours ago, Martin Meredith said:

 There's a fairly recent description with images in this paper and also here.

I've also marked in red a faint mag 19.6(V) quasar with a redshift of 3.12, corresponding to a distance of up to 11.6 billion light years. There are 3 other (closer) quasars in the image, unmarked.

Nicely done Martin, always facinating to see your amazing results.

Thanks for the refs., (nice to see Arp being taken seriously these days ) they are a bit above my paygrade though, l iked the pics in the second, looking just like yours  !

Quasars : there are a lot about !  and are there one or two other galaxies lurking in there as well ?!

[johnrt]

Yep I can see the bridge, well captured and a fascinating image. Excellent!

[Martin Meredith]

Thanks very much Helen, elpajare, Niall, SilverAstro and John.

SilverAstro, you're right, the pics in that second paper are remarkably similar, considering, even down to the feature where the tail meets the upper galaxy at the left. It's great what we can do these days with modest equipment. It never fails to amaze me when I carry the scope out at night and peer down at the grubby mirror what a mere 8" piece of glass can capture (not forgetting the Lodestar!).

And there are definitely more galaxies in there. Surprisingly, I can make out a mag 20.7 (PGC 3362149) at 5.4 billion LYs at around 8 o'clock with respect to the lower galaxy. Here's a chart. There's another bunch just south of my dust shadow...

UMA6379.pdf

Martin

[SilverAstro]

8 hours ago, Martin Meredith said:

what a mere 8" piece of glass can capture (not forgetting the Lodestar!).

And there are definitely more galaxies in there. Surprisingly, I can make out a mag 20.7 (PGC 3362149) at 5.4 billion LYs at around 8 o'clock with respect to the lower galaxy. Here's a chart. There's another bunch just south of my dust shadow...

UMA6379.pdf

and with just a few half-seconds !

It was the two on the edge at about half-past 4o'clock and the other half way to the edge at 6o'clock that first caught my eye.

Thanks for the chart, amazing detail. At first though I had trouble matching it with your image, I presumed a simple rotation, no flips or mirrors, seemed to fit the two ARPs but a lot didnt match   but then I found three P galaxies and an SSDS that matched (added in red below) The object I've marked A threw me for a long time, thought it looked like a rival galaxy but not marked on the chart,  so just a variable star ?

What is the thing marked SSDSetc I presume Sloan Digital Sky Survey but which one of what I've not figured out yet.

Thanks, very interesting and kept me out of mischief for a while

 

[Martin Meredith]

Nice work! I think you'll find that A is on the chart, just diagonally above the 4 in Arp 104. The chart is a bit deceptive relative to an image in that bright stars (that one is mag 12.1) are somewhat overexposed. Having said that, in the next release of the charts I'm aiming for a more considered stellar brightness representation.

The SDSS thing marked is another quasar (mag 19.5). 

(the technical doc describing the map symbols is here)

Just to add that I'm forever having to do mental gymnastics re these charts when I'm at the scope, trying to ensure I've got the right target. It wasn't a problem here because the galaxies are quite bright. What I'd really like is to be able to do a software rotation at the scope to align N up. 

Martin

[SilverAstro]

3 hours ago, Martin Meredith said:

Nice work! I think you'll find that A is on the chart, just diagonally above the 4 in Arp 104. 

Yes  sorry, I was not clear, on the chart I saw just a tiny dot at that location, but a large object in your image, which threw my orientation experiments ! After I had sorted myself, with/in the blink, I then wondered if it might be an object of further interest.  Thanks for your explanation, all makes sense now