The invisible arms of NGC 1512

[strongmanmike]

NGC 1512 is a lovely ring galaxy with a prominent bar and companion galaxy in Horologium. It's quite modest in size with the main visible component around 9' X 5' and shines at Mag 11 with a low surface brightness of just 22.7 mag/squ arc sec

The cool thing is, I saw a Galaxy Evolution Explorer Satellite (GALEX) image taken in UV of NGC 1512 and it showed some otherwise invisible or almost invisible (in visible light) outer arms extending a long way form the galaxy plus a bit of a tangle of shorter faint arms, all looking like a complex history of interactions...and I thought hmm? I wonder what the AG12 could get with a bit of exposure time :question:

Well here is the answer :D

NGC 1512 (http://www.pbase.com/strongmanmike2002/image/153237317/original)

Inside the core (http://www.pbase.com/strongmanmike2002/image/153237509/original)

Comparison with GALEX satellite image (http://www.pbase.com/strongmanmike2002/image/153249771/original) (hopefully I'm not a deluded emperor this time :lol:)

Comparison with UK Schmidt (http://www.pbase.com/strongmanmike2002/image/153348038/original)

Well..at 10hrs it is almost Mega data Paul and since it was through a 12" at F3.8.. is probably equivalent to about 50+hrs through a 4" @ F8 ;) and marks the longest exposure I have taken so far with the AG12 YAAAY :P

[renormalised]

You keep excelling yourself every time I see a pic you take. This is no exception and it's a damn great shot :)

[Stevec35]

Nice Mike! Definitely no substitute for a bit of exposure.

Cheers

Steve

[prokyon]

Great, the arms are visible now! :thumbsup:

[alpal]

That's a great shot Mike -
I can't find a better amateur pic of NGC 1512.

cheers
Allan

[RickS]

Very nice work, Mike! Good to see you getting with the megadata program :D

[Tom Davis]

Lovely, Big Mike.

[tilbrook@rbe.ne]

Great work Mike!

Like the full field version best, the spiral arms look like they have been disrupted.

Cheers,

Justin.

[Larryp]

Lovely image, Mike :thumbsup:

[multiweb]

Very cool shot. :thumbsup:

[strongmanmike]

Thanks for checking it out and passing comment guys :thumbsup:

Thanks a lot Carl, I am really enjoying imaging galaxies at the moment...could ya tell? :whistle:

Cheers Allan too, glad you think so :thumbsup: I couldn't find many amateur images period :)

Mike

[gregbradley]

What a great find. Superb image Mike. Love it.

Greg.

[Paul Haese]

Yeah I like this one. Maybe a little blue magenta, but heaps of cool detail.

For the record though it is a 4" f5.6, so that would make it 28 hours instead of 50.:P

Needs more data though still.;) Another 10 hours it would look slick, slick slick.:) So mega up dude.:P

[Bassnut]

Excellent work Mike, most impressive. Fair pops out of the screen.

[strongmanmike]

Cheers boys :D :thumbsup:

[RobF]

Whoosh - right through the hoop. What a shot :clap:

[strongmanmike]

Ahh huuuh.... :rolleyes:

Soooo, a galaxy I have NEVER seen posted on IIS before :question: and it reveals things that are outside the realm of the usual NGC 253 or Lagoon Nebula (love the Lagoon Marc :love:) aaaand it is just too magenta/blue?? :doh: geeeez :scared: :lol: :thumbsup:

3 X the aperture and two F-stops...hmmm? I think the mathematicians out there might be able to clarify things here...any takers? :D :thumbsup:

Thaaanks Paulie :)

[John Hothersall]

That's a good pick up of the faint arm, Eridanus has so many galaxies perhaps you could try NGC1532.

John.

[stevous67]

Nice job Mike,

Steve :thumbsup:

[strongmanmike]

Yeah thought about it but for some reason it doesn't grab me :question:...no idea why as it's a pretty cool looking galaxy huH?



Cheers Steve

[strongmanmike]

Hey, a magenta/blue lover huh? :lol:

Cheers Rob, glad ya liked it...10hrs was long enough for me :zzz2: ..I will do better at some stage though :D

Mike

[Shiraz]

Really outdid yourself this time Mike - what a cracker of an image, Nice that you are regularly seeing stuff that no-one else seems to.

[strongmanmike]

I'm deluded...but I do believe the statement in my signature :lol: :thumbsup:

Cheers for the nice comment Ray :2thumbs:

MIke

[nandopg]

Hi Mike,
Thank you for sharing such a stupendous image that in the end sets a new standard of reference for all of us, well at least for me.

Best Regards,

Fernando

[strongmanmike]

Hey thanks Fernando, very glad you liked it :thumbsup:

Mike

[cybereye]

Mike,

What can I say - I love your work! :love:

Another fantastic image from "La Casa di Sidonio"...

Cheers,
Mario

[SpaceNoob]

Great image Mike, nice faint structures are clearly visible.

Sure it could do with another 10hrs, but thats enough time for a new target! ;)

[strongmanmike]

Thanks Mother Mario :P



Cheers Chris, glad you could make'em out ;)



Shhhhh :scared3: don't say that mate :scared:

Mike :thumbsup:

[broca]

Beautiful image Mike. It is crazy what you are able to pull out of these galaxies from your skies!

[marc4darkskies]

I guess I've been a little preoccupied! :D Missed this one :rolleyes:

That's a ripper image Mike ... and I CAN see the faint arm! :thumbsup::thumbsup:

Cheers, Marcus

[strongmanmike]

Cheers Steve and yes darker skies certainly make a lot of difference :thumbsup:



He he, there are a lot of old myopic eyes out there ;)

Mike

[David Fitz-Henr]

That's a lovely image Mike; some faint arms there with that large outer faint arm at the top looking quite impressive!
A general question / thought regarding the presence of magenta in galaxy images - given that spiral arms contain copious amounts of hydrogen as well as hot blue stars I wonder whether there should be a little magenta in these images? If the data supports it and the stars look balanced, perhaps the colour selection tool in PS should not be used that aggressively as in many images I've seen?

Anyway, looks good to me Mike :thumbsup::thumbsup:

[strongmanmike]

Cheers Dave :thumbsup:

Hey you may well be right about the magenta :thumbsup: aaaand I have been criticized for it :sadeyes: :lol: but in the end it is a pretty minor issue really and is more obvious to some than others. Each galaxy image seems to come together a little differently from a colour perspective, besides there is sooo much more about an image of a distant island of billions of stars with complex faint structures and jets (:rofl:)...than any minor colour bias fixation :)

[strongmanmike]

Here's a comparison with a deep image by the UK Schmidt

Deep Image NGC 1512 (http://www.pbase.com/strongmanmike2002/image/153348038/original)

It is clear modern sensors can make small telescopes more sensitive than using chemical emulsion on very large telescopes :thumbsup:

Mike

[RobF]

Impressive for sure

[madbadgalaxyman]

Very interesting, Mike.

The outer extremely-faint arms have a very unusual pattern.

The galex Far-ultraviolet band is very sensitive to the light from even relatively small numbers of hot young OB stars ( = recent star formation), so you are doing very well to pick up the blue knotty outer arms of this galaxy.

The arm pattern near the satellite galaxy is indeed distinctly weird.

This H-alpha image from the SINGG survey (with H-alpha image displayed as Orange) (H-alpha line only is coded as orange, because stellar light was subtracted from the H-alpha image) shows some of the outer arm material. The fact that the arms are luminous in Ha is proof that the knotty material consists of hot young OB stars.
Another interesting feature is that the little satellite galaxy looks bright in H-alpha, so it is likely to be very vigorously forming stars.

151640

[glenc]

That is an amazing image Mike.
Here are the first descriptions of NGC 1512.
https://picasaweb.google.com/110048826379679252146/Dunlop28#5356128767992263970
They were made by James Dunlop in 1826 and John Herschel.
Dunlop 466 "A small faint round nebula; about 25" diameter, a little brighter in the centre: a star of the 10th or 12th magnitude preceding the nebula."
Dunlop discovered about 50 galaxies.
https://picasaweb.google.com/110048826379679252146/Dunlop28#

[strongmanmike]

Thanks for checking it out guys :thumbsup: Seems that long outer arm is full mostly of new stars then..?

Mike

[madbadgalaxyman]

Hi Mike,
Yes, indeed....something is making those new stars in the outer regions of this galaxy, so it must therefore follow that there is lots of gas and lots of energy out there, even though there is not much visible in the outermost regions apart from the very faint and unusual arms.

I am certain (at about the 99 percent certainty level) that the outermost arm is experiencing current star formation;
there are usually O and B stars formed in a recent vigorous Star-Formation episode, and these hot young over-luminous stars:
(1) are very prominent in the far-ultraviolet, so they light up like flares in the GALEX satellite images
(2) will light up the gas in the surrounding gas clouds from which they formed, by ionizing the gas and making it glow in Ha, as it requires short wavelength ultraviolet photons from massive luminous new stars to produce an HII region.

One interesting question is, "why should stars form so vigorously, so far from the main optically-bright body of NGC 1512?"
Something has to give interstellar gas a really hard "hit or shock" in order to get it to contract and to form new stars.
So a strong shock wave is required in the outer regions of this galaxy, and also a supply of interstellar gas is needed in order to make the new stars.

It has got me speculating as to whether an encounter with the little companion galaxy might be responsible for the unusual pattern of the outer arms; but the mass difference between the primary and secondary galaxy must be significant. You really need a lot of gas and a lot of energy to make the very-luminous "new & blue" stars that are evident in the outermost arm.

Here is the Galex far-ultraviolet plus near-ultraviolet image, using the GalexView interface. FUV displays as blue, and it is almost certain that the bright knotty FUV emission of the outer arms is coming from newly-formed "hot & young" very-luminous stars.

151733

[strongmanmike]

Well it looks to me Robbo like something was doing burnouts and doughnuts around this galaxy and has whipped the arms into threads...perhaps the little companion galaxy is the culprit? :)

Mike

[cosmophoton]

Perhaps a problem in my monitor? Is that only my impression, or is Mike's AG12 image in fact much better than the Schmidt's one? :)
Cheers,
Luiz

[madbadgalaxyman]

Sounds like the revhead theory of spiral arm formation!

This is a very strange galaxy, in its way, as the question can be asked "why aren't there bright spiral arms in its outer regions, like there are in other spiral galaxies?" Why no bright arms? Perhaps there will be some bright arms, sometime in the future?

Take a look at the following image, which overlays the gas distribution in the outer region of this galaxy with the thin & knotty spiral arms that are seen both in your image and in the GALEX image.
(the cold gas, invisible to the eye, is displayed as green, and the Galex ultraviolet image is displayed as blue)

As you can see, the HI gas (the cold atomic hydrogen gas) forms a sort of "super-sized" spiral that surrounds the visually bright part of this galaxy (the bright part of this galaxy is composed of the ring that surrounds the bar, plus the bar that is inside the ring.).
The interstellar gas in this galaxy extends to many times the radius of the prominent and bright ring structure, which shows that this galaxy extends a long way further out than we think it does.

151778

However, the distribution of stars (as traced by visible light) seems to be very concentrated and bright only till we reach the outside edge of the bright ring structure..... and then the surface brightness suddenly drops drastically outside of this ring structure.
So we have here a galaxy which has formed plenty of stars in its inner part, up to the radius of the bright ring, but which has formed hardly any stars outside of this ring.
(well, there do exist the thin arms outside of the bright ring, but this is hardly a grand and bright spiral structure)

Given that the gas in this galaxy is distributed in a spiral, and that the thin and knotty outer spiral arms seem to be forming in the places where this spiralling gas is the most dense, it would seem that the cause of the thin knotty arms in the outermost regions must be connected with the spiral-like structure that is seen in the underlying gas
( you can't form the stars in spiral arms without having dense gas existing there in the first place, as a raw material for the star formation process.)

There is definitely "plenty of this galaxy existing outside of the bright optical part that is defined by the ring", but most of it is just interstellar gas that is distributed in this very extended spiral pattern.
Perhaps one day, the big gaseous spiral that is outside of the obvious part of this galaxy will form enough stars to make some really bright spiral arms!

My personal view is that this galaxy just needs some more time to evolve, and that the outer gas spiral may one day turn into the bright spiral structure that we are used to seeing in other galaxies.......

[strongmanmike]

Interesting...so you think the spiral arms might actually be in the formation stage then..? Didn't consider that :)

Mike

[Ross G]

A beautiful galaxy photo Mike.

I think the best from your current series with the new camera.

I love the colour and the faint detail you have brought out is amazing.


Ross.

[madbadgalaxyman]

Yes, I do think that the very-large-scale spiral structure in the extremely-extended outer gas distribution of this galaxy might eventually form lots of stars (instead of forming just a few narrow & faint arms with a few OB stars along them, which is all that this gas has recently formed)

This galaxy is strange, because in nearly all of the other barred spiral galaxies that have a ring structure that surrounds a bar structure, there is plenty of bright spiral structure visible outside the ring;

In contrast, the surface brightness of this galaxy is high till we reach the outer radius of the bright ring, and then.......BANG! the surface brightness suddenly drops to very low levels just outside of the ring.
It is a matter of the density of the stars being high within the radius of the ring, and the stellar density being very low outside the radius of the ring.

I think that an interpretation consistent with the facts is:
- that the inner part of this galaxy has formed in a normal way
- that the outer part of this galaxy is mainly in gaseous form rather than in the form of stars
- that the outer spiral-shaped gas distribution has the potential to form plenty of stars, given sufficient gas density and given sufficient time
- that, given enough time, bright and prominent high-surface-brightness Optically Visible spiral arms might form from the gaseous spiral arms

Best Regards,
Robert Lang

Lopez-Sanchez and Koribalski in 2009 wrote a paper about the gas and stars in the outermost regions of this galaxy; I have got it, but haven't read it yet, as I don't want to be prejudiced by their interpretation.

[Elio]

Stunning image Mike, as ever yours... ;-)

[jase]

Stunning barred spiral Mike. Forget the core crop, one must admire the outer reaches of the spiral arms in order to fully appreciate what you've put together. Top stuff.

[strongmanmike]

Thanks gentlemen...something a bit different to image - always good huh Jase? ;) :)

[Rod771]

Excuse my tardiness Mike :)

What a fantastic image, congratulations!

Great thread too , interesting info.

Cheers

Rod

[strongmanmike]

Well....I wasn't going to speak to you ever again :confused: :mad2:

Buuuut I forgive you Rod :innocent: :lol:

Glad you liked the view :)

Mike

[Nicola]

Very nice image of a fine galaxy, well done Mike.

[astronobob]

The Artiest at work again, very nice looking target and nice work resoving the faint extensions etc. Brilliant '10hr' snap Mike :eyepop: Youd be getting close to Imaging time being less than processing time eh Mike ;) :thumbsup:

[strongmanmike]

Cheers Nicola



Cheers Bob, yes, exposure time and processing time were probably pretty close on this one :)...I am a bit of a time waster though, what with all the research for the comparisons etc :question:

Mike

[allan gould]

Very cool galaxy with a lot of detail there Mike. I like it a lot and it shows what a great scope can achieve.
Just one small quibble - and that's the title. An invisible arm is just that, if you imaged them they ain't invisible. :thumbsup:

[strongmanmike]

Cheers Allan :thumbsup:

Ah yes..t'was meant to be a contradictory title...now wait to see if Rick can prove my cloths aren't invisible too ;) :lol:

Mike