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Old 29-05-2024, 10:01 PM
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rmuhlack (Richard)
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M83 with halo and extended loop

The Southern Pinwheel Galaxy (M83) is an astrophotography favourite at this time of year. The galaxy lies at a distance of around 15 million light years in the southern sky constellation of Hydra, and I’ve recently learned that it has a few tricks up its sleeves when subjected to longer exposure times, especially from a dark(ish) imaging location.

A 1997 research paper by astronomers David Malin (Anglo-Australian Observatory, NSW) and Brian Hadley (Royal Observatory, Edinburgh) describes unusual faint features that can be revealed in very deep images of even well-known galaxy targets, including M83. They present image data collected by the UK Schmidt Telescope at the high-altitude Siding Spring Observatory in Coonabarabran NSW, including a deep image of M83 which reveals “an enormous loop around the NW quadrant of the galaxy.” They also make mention of a “very extensive H1 halo with 80 percent of the detected H1 beyond the Holmberg radius [ie what is usually regarded as the galaxy’s “edge”], much more than is normal in such galaxies.”

[Ref: Malin, D & Hadley, B 1997, ‘HI in Shell Galaxies and Other Merger Remnants’, Publications of the Astronomical Society of Australia, vol. 14, no. 1, pp. 52–58.]

My image consists of about 20 hours of OSC broadband colour data combined with about 2.5 hours of narrowband hydrogen and oxygen (via a OSC dual band filter). The extended “halo” is quite obvious, though a little more work is required to see the loop. I’ve included here the full field-of-view, an inverted (and significantly stretched) image to better showcase the “loop”, a crop to show the full-res detail of galaxy core, and finally some relevant excerpts from the Malin and Hadley paper.

Skywatcher 200PDS, Sharpstar 0.95x MPCC, QHY294C, NEQ6
Optolong UV-IR, 243 x 5min subs
Optolong L-Extreme, 14 x 10min subs
Image data collected from Strathalbyn SA. Processed with Pixinsight.

full res: https://www.astrobin.com/ogs7rg/
Attached Thumbnails
Click for full-size image (M83 90bb 10nb process 1sm.jpg)
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Click for full-size image (M83 90bb 10nb invert process 1 annotated sm.jpg)
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Click for full-size image (M83 90bb 10nb process 1 crop sm.jpg)
106.3 KB41 views
Click for full-size image (Malin abstract.JPG)
99.8 KB19 views
Click for full-size image (Malin M83 discussion.JPG)
119.5 KB18 views
Click for full-size image (Malin M83 figure edit.jpg)
158.8 KB26 views

Last edited by rmuhlack; 30-05-2024 at 06:30 PM.
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Old 30-05-2024, 12:53 AM
Bodon (Steve)
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Richard nice detail there!
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Old 30-05-2024, 09:13 AM
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A very appealling image. Well done Rochard.

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Old 02-06-2024, 10:42 PM
Dave882 (David)
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Wonderful image! And a very interesting write-up as I’d not heard of this halo before. Great work thank you for sharing!
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Old 04-06-2024, 04:15 PM
ahmed_haider (Ahmed)

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Amazing image and thanks for the write up! Really interesting.

In the paper you attached there is a reference to NGC 253 (the silver coin galaxy) having an extension to one side of the galaxy. I'm researching this and can't find what they're referring to
(Or probably its right there and I can't understand it )
The silver coin galaxy in all its glory:
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