Good Old Antennae

[Russ.Carpenter]

I took a break from tiny weird galaxies and imaged a big weird galaxy. This text and image were uploaded to Astrobin this morning. https://www.astrobin.com/a7l2s4/

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This image is part of my on-going investigation of peculiar galaxies in the Southern Hemisphere. I’m pleased that this image so clearly shows the interior details of the Antennae system and the tidal dwarf galaxy at the end of the southern arm.

Is there a more interesting, and famous, pair of colliding galaxies than NGC4038 and 4039? I was so immersed in the research on this object that I stopped imaging for a while. One could write a book on the Antennae system.

The Antennae system is our closest example of a major galaxy merger. It has been intensively studied by some of most expensive and sophisticated observatories on the ground and in space. These studies have often been aimed at one or more dwarf galaxies that have formed at the end of the southern tidal tail.

“Galaxy Collisions” by Curtis Struck has an excellent description of this tidal dwarf galaxy. I’d like to quote two paragraphs:

“The bow is what has come to be called a tidal dwarf galaxy, or TDG. In several ways TDGs are the strangest galaxies in the universe. If the most wide accepted model of galaxy formation is correct, all galaxies started off as dwarfs or as collections of dwarfs. Most of the dwarf companions to the Milky Way may be remnants of such early dwarfs. Like the majority of galaxies, these dwarfs formed after primordial gas fell into a dark matter well that formed still earlier. In the gravity well of these halos the gas was compressed and formed the first generation of stars.

The known TDGs did not form at the beginning of the universe; they appear to be forming now. The evidence suggest that they are just about the only class of galaxy that is forming in the present-day universe. Moreover, they do not form at the bottom of a pre-existing gravity well, but rather out on the end of a tidal tail. That is, in material that has been thrown as far out of the central gravity well as the interacting galaxy can manage.”

The Antennae system was cataloged in Halton Arp’s original Atlas of Peculiar Galaxies but was not included in the Catalog of Southern Peculiar Galaxies and Associations, because its declination is north of that catalog’s limit of -25 degrees.

Tech Notes for ASA 500/3.6:
ASA Newtonian, 500 mm aperture, 1900mm focal length, F3.6
FLI Proline 16803, 9 mm pixel, 4096 X 4096
ASA DDM85 equatorial mount
Processing with PixInsight, StarTools, and Affinity Photo