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View Full Version : Object of the Week, November 29, 2020 - Arp 236 = IC 1623 train wreck



Steve Gottlieb
November 29th, 2020, 10:24 PM
Name: Arp 236 = VV 114 = IC 1623A + IC 1623B
RA: 01 07 47.2 Dec: -17 30 25
Constellation: Cetus
Type: Interacting collision!
Size: 1.2'x0.9'
Mag: 13 or brighter?
Distance: ~270 million l.y. (redshift-based)
IC description: "bright, considerably small, little elongated, north-following of 2 [with IC 1622]"

This fascinating pair of galaxies was discovered by Lewis Swift on November 19, 1897 at the age of 77, a couple of years before he lost his eyesight. He was observing with his 16-inch Clark refractor at the Lowe Observatory on Echo Mountain above Pasadena.

4115

Arp placed the pair (Arp 236) in his unusual category of "Appearance of Fission" -- in the process of dividing or splitting apart. He added the comment "faint outer arm curves around through 270°." Instead, this is highly disturbed contact pair that's apparently undergoing a major merger. The two nuclei are separated by only 15 arc seconds. This early-stage merger has triggered a burst of young clusters, particularly visible in the western (right) galaxy, but research shows the IC 1623B (the eastern galaxy) is optically obscured by several magnitudes and is very bright in the infrared indicating intense star formation.

The Hubble image has the following description:

"IC 1623 is an interacting galaxy system that is very bright when observed in the infrared. One of the two galaxies, the infrared-bright, but optically obscured galaxy VV 114E, has a substantial amount of warm and dense gas. Warm and dense gas is also found in the overlap region connecting the two nuclei. Observations further support the notion that IC 1623 is approaching the final stage of its merger, when a violent central inflow of gas will trigger intense starburst activity that could boost the infrared luminosity above the ultra-luminous threshold. The system will likely evolve into a compact starburst system similar to Arp 220. IC 1623 is located about 300 million light-years away from Earth."

Pretty cool , right? Yet, I've only run across a few amateur observations of this pair including Alvin Huey's. Arp 236 isn't a difficult object to view, though "resolving" the two nuclei is a tougher challenge.

Here's my observation through my 24-inch f/3.7 Starstructure:

"IC 1623A, the brighter western component, appeared fairly bright, fairly small, round, 25" diameter, high surface brightness. IC 1634B, attached on the east end, appeared as a fairly faint, small glow that wasn't separately resolved, but appeared as a bulge or knot on the east end. 365x revealed a broad concentration with a brighter nucleus. IC 1622, situated 3.1' SW, appeared fairly faint, round, 25" diameter."

And as we always say,
“Give it a go and let us know!”

Howard B
December 1st, 2020, 04:22 AM
Nice choice Steve, and it turns out I have an observation of this interacting collisional pair from a few years ago with my 28-inch scope:

"This is pretty cool - 1623 look like two galaxies in in contact, with B looking like an edge-on. 408x, 21.62 SQM."

4116 4117

I remember this night as looking brighter than the SQM was reading, and the seeing was pretty soft, so this is a good reminder to give this one another go.

Uwe Glahn
December 2nd, 2020, 04:26 PM
What a cool object Steve. I've logged one observation with my 27-inch under very good transparency and average Seeing. I could pick up five knots, three in the main and very bright western part and two in the much fainter extension to the east. South of the row of knots I could see some diffuse nebula, not in the size the HST shows but definitely not as sharp as the longish northern edge.

sketch: 27", 419x-586x, NELM 7m0+, Seeing III
4118
home (http://www.deepsky-visuell.de/Zeichnungen/IC1622_IC1623.htm)

Dragan
October 26th, 2022, 06:04 PM
If anyone is interested, JWST imaged IC1623 recently. And the results are nothing short of amazing.

https://www.space.com/james-webb-telescope-star-formation-galactic-crash-photo

Hi res image is below. The amount of detail in background galaxies is just astonishing.

https://scitechdaily.com/images/Webb-Interacting-Galaxies-IC-1623.jpg