Object of the Week April 28, 2013 - Keenan’s System

Object of the Week April 28, 2013 Keenan’s System

Keenan’s System, ARP 104, VV33

Ursa Major

NGC 5216, UGC 08528, MCG +11-17-004, CGCG 316-019, CGCG 316-019, PGC 47598
RA: 13 32 6.9
DEC: +62 42 03
Size: 1.9’x1.1’
Mag: 12.7V 13.6B
SB: 14.0
Morphology: E0 pec

NGC 5218, UGC 08529, MCG +11-17-005, CGCG 316-020, CGCG 317-003, PGC 47603
RA: 13 32 10.4
DEC: +62 46 04
Size: 1.8’x1.2’
Mag: 12.3V 13.1B
SB: 13.2
Morphology: SB(s)b? pec

Imagine this. Start with two relatively bright, undistinguished galaxies. Then separate them by 22,000 light-years. Finally throw in galactic debris connecting the two. The result is Keenan’s System, aka ARP 104 and VV33.

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The galaxies NGC 5216 and NGC 5218 were discovered and cataloged by William Herschel in 1790. Edwin Hubble studied them as Intergalactic Nebulae in 1926. Then in 1935 on a photograph taken with the Yerkes 24-inch reflector Philip C. Keenan noticed a “faint but definite band of nebulosity” connecting the two galaxies. He also noted a “short curved arm” continuing beyond the other side of NGC 5216. Keenan published a paper with his findings, however it received little notice for decades.

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In 1958 this pair of galaxies was “rediscovered” by observers at Lick and Palomar Observatories. The pair was included in The Catalog of Interacting Galaxies as VV33, published by B.A.Vorontsov-Velyaminov in 1959. In 1966 they were included as Arp 104 into Halton Arp's Catalog of Peculiar Galaxies.

A recent study by Beverly Smith (et al) with the Spitzer Infrared and Galaxy Evolution Explorer UV Space Telescopes has shown the bridge to be a remarkable filament. It revealed "beads on a string" - a series of star-formation complexes. According to their findings, "Our model suggests that bridge material falling into the potential of the companion overshoots the companion. The gas then piles up at apogalacticon before falling back onto the companion, and star formation occurs in the pile-up."

Here are my somewhat sparse observation notes on Keenan’s System aka ARP 104

March 24/25, 2012 at the Cosmic Cowboy Observatory - Barbarella (Jimi’s 48” f/4)
Seeing above average, transparency 7/10, SQM 21.75
Brandon 24 at 203x and Ethos 13 at 375x
bridge between 2 galaxies [seen with] direct vision in both eyepieces
[E13] some brightening in bridge 1/3 way up from 5216
5216 condensed, stellar core
5218 elongated

In addition to the bridge both galaxies have a countertide - a fingerlike extension pointing in a different direction to the debris trail, a typical structure of interacting double galaxy systems. I have no recollection whether I saw either countertide – my sparse notes don’t make mention of either a positive or negative observation.

Observing the galactic bridge, in this case, was rather easy between 48 inches of aperture and the dark, transparent skies of southwest Texas. Once again the weather pattern this Spring in Ohio hasn’t given me a single night to observe with the Moon out of the way. I am patiently waiting to give Keenan’s System a go with my 15” scope, though this one might be a stretch. Meanwhile let us know your results with both the bridge and the countertides. Be sure to note your aperture and sky conditions.

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“GIVE IT A GO AND LET US KNOW”

GOOD LUCK AND GREAT VIEWING!

This is a really cool object good choice Mark.

I have never looked for the "finger" filaments before. The bridge for some reason in the 48" looks wider than in Images I have seen.

Next time I am at the scope Ill try for the "finger" filaments and do a quick sketch to show how wide the bridge looks to me.

On March 9, 2013 I observed Keenan's System with a 28" f/3.6 Starstucture. I used an 11 Nagler (with no Paracorr), so 233x. I didn't see any connection between the galaxies. But I must admit I presumed it wasn't possible using my size scope (or even Jimi's 48"). Did my presumtion preclude any detection? Maybe. I observed about 80 miles north of San Francisco (at Lake Sonoma). I didn't take a sky reading, but it was quite dark--I had my best view ever of the twin quasar through my scope. I definitely will observe Keenan's System again.
Bob Douglas

Same result like Bob, no sign of the bridge with 27" and fairly good conditions.

The brighter "ears" of NGC 5218 and its inner structure were the only details I could pick up.

This is my observation of Keenan' System a few weeks ago with Jimi's 48:

"The tidal tail between the two galaxies is easy to see and a hint of a second tail is seen with a bit of difficulty. The top spiral (galaxy) has a spiral arm on the right. 11:50pm, 10mm, 21.63 SQM."

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When I looked at a photo of this system afterward I was surprised to see how narrow the main tidal tail appeared because it looked really broad through the 48 inch, nearly as wide as NGC 5216 and 5218. But it was a direct vision object and there was no doubt it looked the way I sketched it.

I have wondered why the bridge looks so much wider visually than images of it . Howard's drawing is just how it looks in the eyepiece of the 48"

I showed several people during the Texas Star party " Keenan System" with the 48 and all were surprised at how wide the bridge appeared in the eyepiece.

Correction (via edit): What I describe below was Arp248 or Wild's Triplet and was not Keenan's system. I have left text below but corrected it.

Steve Gottlieb brought up Arp248 in his 24" StarStructure on the last new moon. In looking at this system last new moon at 3000 feet with very good transparency it seemed to me that an extension of 1/4 to 1/3 of the gap was detectable to me. This was detected from the MCG-1-30-33 side only for me. After stepping down from the ladder I had my doubts that I had seen it so I went back (thanks Steve) and was able to convince myself that it had NOT been 'averted imagination' or if it had, that effect had happened while I was trying hard to be 'honest'. So I feel at least part of this bridge can be detected in a 24" scope but only just.