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Old 26-11-2020, 11:40 PM
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strongmanmike (Michael)
Woohoo it's clear

strongmanmike is offline
Join Date: May 2006
Location: Canberra
Posts: 15,407
Fornax A - shells, massive halo and recently identified faint loops and tidal tails

I recently did a deep image of Fornax A (NGC 1316) and a mate, Scotty Alder (Tornado33), made an interesting comment regarding this image on Facebook, that got'a me to a thanking....hmmm?

Scott commented that he would like to see me push my big fast scope to see how deep it can go, hey a bloody great idea ...but then I thought, hmm? I took 10hrs of Luminance data with a 300mm dia scope at a fast F3.8 under reasonably dark skies, so I wonder just how deep I had already managed to go..?

So I searched for deep images or even better, quantitative empirical papers on the brightness of some of the faint outer tidal tail regions of NGC 1316. Well low and behold it didn't take long and I found one

A paper by E. Iodice et al from 2017 shed some very interesting light on my enquiry. This paper used deep imaging data from the ESO VLT Survey Telescope (VST) a 2.6m F5.5 modified Ritchey-Chretien optical layout with a two lens wide-field corrector and located at Cerro Paranal in Chile.

In fact this paper revealed that some of the very faintest structures captured in my data were only identified as recently as 2017 and reported in this paper, the faintest of which (labelled L9 in the annotated image at the link below) shine at an almost impossibly feeble 30.1 mag/squ arc sec!! (which is about 2000X fainter than the core region of the galaxy!)...but never the less, still detectable with amateur equipment

So the initial answer to Scotty's question is..well? in 10hrs worth of 10min exposures through my 12" F3.8 Newt, using a modern commercial cooled CCD camera (SXVR-H694) we can record faint structures with surface brightness's fainter than 30mag/square arc sec!...that's BLOOD this case, so faint in fact, that even for a significant and regularly studied galaxy like NGC 1316, they weren't identified until just 3 years ago!

Here is the image analysis showing the depth reached (remember to have your screen adjusted properly with brightness turned up as these features are very faint)

The full colour image is HERE

A reminder to look deep and carefully into your data, you never know what you might dig up or discover

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Click for full-size image (NGC1316 new outer shells labelled small.jpg)
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Last edited by strongmanmike; 27-11-2020 at 12:01 AM.
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