Arp 105 & Abell 1185 (Gary Imm)

Arp 105 & Abell 1185

This image captures a galaxy group located 400 million light years away in the constellation of Ursa Major at a declination of +29 degrees. Although the image shows many interesting galaxies from Abell 1185, the highlight is Arp 105 on the left. This collision between a spiral and an elliptical galaxy, along with the resulting star streams, stretches 6 arc-minutes in our apparent view, which corresponds to a span of 700,000 light years! Arp 105 contains 5 galaxies easily seen in this image and a number more which are too small to be seen. I have included an annotated image to help with the description below.

Starting from the very bottom of the lovely mess that is Arp 105 and working up, the stellar-like small blue object is known as Ambarzumian's Knot, believed to be a newly formed tidal dwarf galaxy. I am always intrigued why certain objects are named after individuals. No doubt that Ambarzumian identified this knot (in 1957) and it was named after him, but I don't really understand why this particular feature was given a name. Perhaps because it is small and bright.

Just above Ambarzumian's Knot is the large elliptical galaxy NGC 3561B. Just above it, and interacting with it, is the disturbed spiral, NGC 3561A. Just above and left of the spiral is another new dwarf galaxy (VV237d). At the very top of Arp 105 is a much less dense irregular galaxy (VV237f), also newly formed from the tidal star stream.

Aside from Arp 105, the image contains many other interesting galaxies, all part of the Abell 1185 cluster. In fact, very few stars are seen in this image - most of the bright objects are galaxies, as seen in the annotated image. NGC 3550, with the appearance of a galaxy triplet, is fascinating. I also like the shape of PGC 83459, found on the right edge halfway down the image.

Final
Original
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Description: Field Annotations

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Description: Comparison to Original Arp Image

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Abell Galaxy Cluster Catalog (27)
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Status	Advanced success
Started	...
Astrometry.net job	3176619
PixInsight job	TG8FSRTDLWM7F226QJ8LJIIJTTHTKPID
PixInsight queue size	n/a
PixInsight stage	n/a

RA (center)	11h10m59s.999
RA (top/left)	11h11m38s.972
RA (top/right)	11h10m15s.837
RA (bottom/right)	11h10m21s.830
RA (bottom/left)	11h11m43s.952

Dec (center)	+28°42′48″.81
Dec (top/left)	+28°50′10″.60
Dec (top/right)	+28°48′38″.50
Dec (bottom/right)	+28°35′25″.84
Dec (bottom/left)	+28°36′58″.60

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