The curious case of M63

[Guest]

So I wasn't sure where exactly to post this, as I am not one to just post pretty pics, but rather in discussing things relating to imaging.  So I took over 17 hours of data on M63, and I pushed the data a bit over the top to show what I think might be some faint details I haven't seen elsewhere:

https://photos.app.goo.gl/7q5Nwu99354jzhRt7

So, the two tidal arms on top and to the right side I've seen fairly common.  What I haven't seen though is the extensive fainter whisps and whorls farther out.  I found this paper from back in 2011 discussing the tidal arms and especially the extended tidal area around M63:

https://iopscience.iop.org/article/10.1088/0004-6256/142/5/166/pdf

 

On page 10, figure 9, they show the observed ellipse tidal arm (in red) but also a predicted tidal ellipse in blue which at the time they didn't observe.  I've seen bits of that blue ellipse in other images, and the extra data in mine seems to fit.  What do you guys think?  Is it real or some sort of artifact from my processing?  I did use blurx and noisex and starx, and nothing else other than masked stretch, curves and saturation.  I spent a few hours undoing blurx and noisex and just using curves, and while extremely noisy, it did seem to hint at those structures also.  I honestly don't know.

 

[Guest]

Here's the completely overstretched image with nothing but curves applied to it and converted to grayscale.  This was straight after integration, crop and gradient extraction in APP.

 

Edited February 14 by dciobota
Oops, I had a tiff uploaded instead of the jpeg, sorry.

[wimvb]

Very impressive. I think that what you have is real. R.J. Gabany and David Martinez-Delgado are both authorities in the field of very deep field astrophotography.

One tip: in order to see what is in an image, I usually invert the linear L and "superstretch" it by bringing in the black point and the white point until I can see all features, including ugly artefacts from imperfect flat calibration and such. Inverting the image makes it easier to see faint differences in signal.

[Guest]

Oh good point, I've noticed people doing that.  I'll go an try it and see if it shows the background better.

Yeah that paper caught my eye also because it was based on work by Ray Gralak, a very talented and respected imager in our amateur community.  Interesting how amateur work can lead to such great scientific discoveries.  Fascinating stuff.

 

[michael.h.f.wilkinson]

The blue ellipse in the paper is due to H-I (neutral hydrogen at 21 cm wavelength). I am not sure how much that region would show up in the optical wavelengths. I would certainly not expect star-forming regions there, but there may be stars, of course. 

[Guest]

Puzzling isn't it, yet some of the wispy stuff in my background seems to roughly match it.  I know the scales are vastly different but I've wondered if some of this could be lit by the galactic disc similar to how interstellar dust is?  I honestly don't know.  I've never actually read about this phenomenon before in a scientific paper, just watched the pretty pics like m51.

[ollypenrice]

Maybe we could ditch the dismissive term 'pretty pictures?' If so I'd be more than interested in joining the conversation.

Olly

[wimvb]

2 hours ago, ollypenrice said:

Maybe we could ditch the dismissive term 'pretty pictures?' If so I'd be more than interested in joining the conversation.

Olly

Please do join the conversation.

 

5 hours ago, michael.h.f.wilkinson said:

The blue ellipse in the paper is due to H-I (neutral hydrogen at 21 cm wavelength). I am not sure how much that region would show up in the optical wavelengths. I would certainly not expect star-forming regions there, but there may be stars, of course. 

Neutral hydrogen wouldn't show up. But it's usually not just gas that is ripped from a galaxy, but also stars and dust. It's just that radio telescopes are sensitive to it, while optical telescopes can pick up the star streams. Anyway, there's some very cool physics going on here.

[Guest]

10 hours ago, ollypenrice said:

Maybe we could ditch the dismissive term 'pretty pictures?' If so I'd be more than interested in joining the conversation.

Olly

I wasn't being dismissive in the least, apologies if it came across that way.  I just meant I don't usually post my pics just for their own sake is all.  It's a personal thing, not meant to be critical of anyone else.  I do enjoy looking at others work.

[Guest]

8 hours ago, wimvb said:

Please do join the conversation.

 

Neutral hydrogen wouldn't show up. But it's usually not just gas that is ripped from a galaxy, but also stars and dust. It's just that radio telescopes are sensitive to it, while optical telescopes can pick up the star streams. Anyway, there's some very cool physics going on here.

So maybe then my background isn't actually real?  Could there be star streams that dispersed and faint to be picked up like that?

Oh and dopey me totally forgot to invert the image.  I'll do that tomorrow.

[wimvb]

1 hour ago, dciobota said:

So maybe then my background isn't actually real?  Could there be star streams that dispersed and faint to be picked up like that?

Oh and dopey me totally forgot to invert the image.  I'll do that tomorrow.

Galaxy collisions, which is what this is about, are very complicated processes. Detecting their products sets very high demands on our equipment, data acquisition and data processing. Even then, we do astrophotography at the very limit of what can be achieved with moderate amateur equipment. (You haven't mentioned what equipment was used to capture this image, but my guess is that it wasn't a multi-telescope rig situated in the New Mexico desert.) But, from what I've seen here so far, your result certainly looks real.

Btw, to learn more about the science and theory of galaxy collisions, I can recommend this book. It helped me to get a better understanding of the subject.

https://link.springer.com/book/10.1007/978-0-387-85371-0?utm_medium=referral&utm_source=google_books&utm_campaign=3_pier05_buy_print&utm_content=en_08082017

[ollypenrice]

My M63 is here.

I'm not totally certain about which outlying features you mean, so maybe you could annotate them on your image?

Mine is quite an old image, processed before the X-suite was available, and I've long been meaning to revisit the linear data. This thread is a good prompt to do so. From memory I was far from confident while distinguishing extensions from gradients, particularly in the lower part of the image, I think the lower right in this orientation. I'll see what happens with a new look today, assuming I can find the original linear stacks.

I've also been thinking about shooting this in the RASA, which would have two advantages. 1) The photographic speed of the setup would find more faint signal and 2) the wider FOV would give the gradient removal software far more information about the structure of the gradient to be removed.  Naturally it would be nice to rely on flats for separating signal from uneven illumination but, for whatever reason, we rarely can.

Olly

[Annehouw]

Here's an oldy from my side (and Bortle 5 site). Originally from an OSC camera, but converted to grayscale and inverted to see the very faint stuff a bit clearer.

Quite real if you ask me, but also very faint indeed.

[ollypenrice]

OK here is my lum data processed only to reveal any outer extensions. It has 14x30 mins, average combined with 36x15 mins (16 hours). I gave it an initial stretch, de-starred it, noise reduced it and then made a copy which I equalized in Ps. This produces absolutely extreme contrasts and brings out the faintest data. I then used the equalized version as a layer mask and stretched again through that.

I would say we have three clear spiral arms on the right, the uppermost one having an angular bend rather like the arms of M101.  What is, perhaps, more relevant to the consequences of an interaction, is the broad band of luminosity which seems to be drawn from the lower edge of the galaxy and out of the field of view in the lower right hand corner. This is the area I struggled with first time around. This time I think it might be a long, broad tidal extension, though the two bright clumps on the edge of the frame here will be starglow from two bright stars. The wider FOV and greater speed of the RASA rig ought to make or break this hypothesis. To be continued.

 

Olly

Edit: Trying to turn this is level of stretch into a presentable image isn't easy.  I think the RASA will do better.

Edited February 16 by ollypenrice

[Guest]

Many thanks for participating guys, and thank you Ollie for sharing your image.  Yes, what you show in the stretched image is what I'm largely talking about.  Mine is a bit wider field and so it shows a bit more of the ellipse area going from top right to bottom left roughly.

 

Anne, yours shows it a bit too!  You can just start to make it out. 

 

Here is my ovestretched and inverted one.  I honestly didn't even bother to make it presentable as I just want to see the faint stuff so you can't even tell where the center of M63 is.  But you get the idea. 

 

I've also clumsily circled the two areas of interest.  The one covering the ellipse in blue that sorta matched the article, and another one stretching to the left. 

 

The article mentioned something about the tidal forces dispersing the material in a sort of rosette pattern, and that's what attracted my attention when I noticed those extra "whorls" or arms for a better word I guess.  It looks like the deeper you go the more this faint stuff might start to look like that rosette pattern.  But then again, it might be just pushing amateur equipment too far and seeing artifacts.

As far as the details of the image.  They's on the photo web page, but nothing spectacular:

at115edt (I think telescope service has a similar scope they sell, a triplet f7)

asi2600mc duo, no filters

205x5 min at 100 gain

My skies are bortle 4-5 depending which direction (sqm around 21).  Those were pretty clear nights and imaging away from the nearby city of Douglas, AZ so it was pretty good transparency and seeing.  Not like in nearby Portal but ok.

I honestly don't know what other info is relevant?  Let me know and I'll do my best.

Thank you all.

[Guest]

13 hours ago, wimvb said:

Galaxy collisions, which is what this is about, are very complicated processes. Detecting their products sets very high demands on our equipment, data acquisition and data processing. Even then, we do astrophotography at the very limit of what can be achieved with moderate amateur equipment. (You haven't mentioned what equipment was used to capture this image, but my guess is that it wasn't a multi-telescope rig situated in the New Mexico desert.) But, from what I've seen here so far, your result certainly looks real.

Btw, to learn more about the science and theory of galaxy collisions, I can recommend this book. It helped me to get a better understanding of the subject.

https://link.springer.com/book/10.1007/978-0-387-85371-0?utm_medium=referral&utm_source=google_books&utm_campaign=3_pier05_buy_print&utm_content=en_08082017

Btw Wim, I totally forgot to thank you for that book.  I'm going to look into it as this discussion and that article has definitely gotten my curiosity going.  I've read bits and pieces over the years about galaxy interactions but not anything on a serious technical level, so this has been an eye opener.  Certainly helps for folks like you and Olly and others who chimed in to more or less confirm that this stuff may be real.  I'm still debating with myself on that, I'll be honest.  My equipment is indeed very modest and my skies aren't all that great compared with say Deep Sky West which is a ways from here or even Rodeo NM or Portal AZ which are not far.  Maybe I got lucky.  Just a few short months ago I was still processing almost exclusively with Photoshop, using APP only for the stacking and some minor pre processing.  A friend of mine convinced me to give PI another try.  I still hate it, but I just follow his very simple workflow and use a few automated tools and get much better results than I used to.  But this makes me doubt these magical tools at the same time... did my data really contain all that info?  Sometimes it's really hard to believe.  Like I said before, I don't normally post to the public, just to myself and friends, but even then, I'm very critical and don't want to deceive even if these images aren't really intended to be used scientifically.  I don't like coming up with detail that isn't really there, and there has been so much discussion about blurx and noisex that I have been triple checking my results against the original to make sure nothing was actually added.  I understand Russ' math and explanations (I used to work in neural nets more than 20 years ago) but you know how it is, extraordinary results require extraordinary proof... or something like that lol.

 

But I'm glad this stirs up discussion and maybe gets some imagers to really dig into their data and see if there is something lurking there that we sometimes miss or ignore, or think it's just an artifact not real data.  I think maybe some folks would be surprised to find there is still data, noisy and ugly maybe deep in there. 

[wimvb]

3 hours ago, dciobota said:

Btw Wim, I totally forgot to thank you for that book.  I'm going to look into it as this discussion and that article has definitely gotten my curiosity going

You're welcome. 

4 hours ago, dciobota said:

My skies are bortle 4-5

That's fairly dark, and the 17 hours you spent on this image shows that your skies are good enough to catch tidal streams.

[ollypenrice]

My interpretation would be a little different. I'm inclined to think that the arms outlined in blue might be normal spiral arms lying in the galactic plane.

The loop outlined in red seems a little odd since it leaves the galaxy and returns to it. The solid red line suggests this strongly. The closely dotted red line might be part of the same loop and the sparsely dotted line is pure speculation. My hunch (no more than that) is that the red loop lies a little out of the galactic plane. From the point of view we have here, I'd put the solid red loop as rising above the galactic plane and the closely dotted loop as dropping below it. In this interpretation the red loop would be the result of interaction.

 

In cross section it would look like this, the galactic plane in blue and the loop in red, as above.

There is pretty good agreement between three independently captured and processed images here and I found that neither StarX nor BlurX had any effect on the faint structures. I used DBE in PI and then stretch in Ps. I begin with a pure log stretch pushed too far and used for reference. My final stretch often involves kinking the curve to emphasize contrasts but I check it against the reference stretch to avoid invention. My rule is, 'Emphasis, yes, invention, no.'

Olly

Edited February 17 by ollypenrice
Clarification

[wimvb]

The most extensive study of the weak structures surrounding the disc of M63 is the one linked to by @dciobota in his original post. The ring structure to the NE of the galaxy is undoubtetly a tidal stream due to a galaxy accretion event. Features to the South and SW are considered to be of uncertain sources, such as the extended disc and halo of M63 (spiral arms as Olly suggests), and possible (older?) accretion events.

On 16/02/2024 at 06:37, dciobota said:

Could there be star streams that dispersed and faint to be picked up like that?

According to the study you linked to in your original post, tidal disruptions caused by older merger events get dimmer over time. The authors of the article speculate about the possibility that there may have been several merger events, with the more distinctive loop to the NE being the most recent.

 

All in all, extremely cool physics, which makes yours a darn pretty picture, if you ask me.

Edited February 17 by wimvb

[gorann]

There are a few deep RASA images of M63 on Astrobin:

https://www.astrobin.com/fl5jg1/G/

https://www.astrobin.com/13e2bh/

https://www.astrobin.com/im68an/

https://www.astrobin.com/tnt25s/

 

[Guest]

Thanks Gorann.  The first one looks the deepest and shows material extending way outside the area I've imaged.  That is interesting indeed.

[Guest]

So this kinda makes me wonder how the 135 Sammy would do wide open in that area for about 20 hours or so?  My thoughts would be that at least from my skies gradients would probably be a big issue, although facing northish is my darker sky area.  Be a worthy project for someone with really dark skies.

[wimvb]

9 minutes ago, dciobota said:

Thanks Gorann.  The first one looks the deepest and shows material extending way outside the area I've imaged.  That is interesting indeed.

That seems to be ifn in the fov. This makes it even harder to determine what the structures really are.

I imaged M63 last year, but because the nights were getting awfully short up here, I never bothered with luminance. Maybe I should do that this year.  https://www.astrobin.com/2wu2wj/B/

[ollypenrice]

38 minutes ago, dciobota said:

So this kinda makes me wonder how the 135 Sammy would do wide open in that area for about 20 hours or so?  My thoughts would be that at least from my skies gradients would probably be a big issue, although facing northish is my darker sky area.  Be a worthy project for someone with really dark skies.

I think that, at Dec 44, we're probably going to pick up IFN, which complicates matters, maybe?

Anyway, interesting stuff.

Olly

[ONIKKINEN]

24 minutes ago, ollypenrice said:

I think that, at Dec 44, we're probably going to pick up IFN, which complicates matters, maybe?

Anyway, interesting stuff.

Olly

SFD dust map is quite weak around M63:

For comparison, here is the dust map around M81/M82 with much stronger signal:

I think there could be a tiny bit of IFN around M63, but unlikely to be shown in significant amount due to its weakness.