IC1459 Group of galaxies

[marco]

Hi all, I have just uploaded a new image centered on the group of galaxies around IC1459:

IC1459 Group of galaxies (http://www.glitteringlights.com/Images/Galaxies/i-bbk2zsZ/A)

IC 1459 is a seldom imaged elliptical S0 galaxy (i.e. large bulge with a minimal or faint disk) about 70 million light years from Earth located in the constellation of the Grus, close the border with Piscis Austrinus and Sculptor. It is an object of 11 mag easily visible in amateur telescopes and is the leading member of a small group of galaxies formed mostly by spiral galaxies. IC 1459 shows a prominent halo on deep exposures. In its vicinity are the barred spiral galaxies NGC 7410 (type SBa), NGC 7418A (SBc, a low-surface-brightness galaxy which is the product of an interaction or a merger between galaxies), NGC 7418 (a bright relatively symmetric spiral),and IC 2559 (SBc). Other conspicuous galaxies imaged in the field above are IC 5270, IC 5269, IC 5264, NGC 7421 (a noticeably asymmetric spiral galaxy) and IC5273.

Full resolution view (last icon at the bottom right) is recommended, there is an impressive number of galaxies in the background visible..

Hope you will enjoy the view.

Clear skies
Marco

[strongmanmike]

Fabulous image Marco Polo, look at that extended halo around IC 1459 :eyepop: awesome! Soooo many galaxies and yes this area is not imaged nearly as often as it deserves, I agree...perhaps because a rather wide and high res field is necessary to do'em all justice and this keeps them a little overlooked?

Although, not as deeply as you have here, I shot'em way back in 2008 from a dark sky too and given their relative obscurity, funnily enough with nearly 30,000 hits now this (http://www.pbase.com/strongmanmike2002/image/101494231/original) is one the most hit images on my web site.

Another great job Marco..hope you get to deliver a paper at an Aussie imaging conference in the not too distant future, you are the master at bringing out super faint details without mega data :)

Mike

[tilbrook@rbe.ne]

Great view on 3x large image Marco!:thumbsup:

Some unusual little galaxies amongst that lot.

Cheers,

Justin.

[RickS]

That's a lovely group, Marco!

[Paul Haese]

Love the variety of galaxy types in the field. Nice composition and colours are good too. Is there a little misalignment at the top of the image? Some of the stars look a little out of registration. Overall a great looking image to me. I think it might need just a little more integration time, but that seems to be just my personal liking. ;)

[marco]

Thanks Mike! I knew your image, actually there are not so many shots around of this lovely area and yours is among the best rendition of it. Interesting to know it had lots of visits, considering not being the most impressive patch of sky out there but still lots of features are visible :)

About me giving a speech at AIC.. :scared3: well, not so sure I could make it ;)



Thanks Justin!



Thanks Rick!



Hi Paul, thanks. I am not sure about misalignment, I believe it is most a effect of the high (excessive?) saturation process that produced some artifacts, but I will double check it..
Surely going longer with the exposure would have helped in reducing the noise (but there are already 5 hours of luminance), even better using a larger aperture or stretch a bit less, trading some faint details for a more noise free overall result.. always a difficult balance decision to make..

Clear skies
Marco

[marco]

I have also added an annotate version of this field:

IC1459 annotated (http://www.glitteringlights.com/Images/Galaxies/i-gbNCqH7/A)

This is a neat feature of PixInsight ;) Interesting that despite reporting all PGC cataloged objects (a database with >73 thousands galaxies) still there are LOTS of background galaxies not labelled. An amazingly rich field of view :)

Clear skies
Marco

[madbadgalaxyman]

Hello Marco,

The 'halo' is better shown than I have ever seen it before!! (I have been looking for a good image of the outer parts of this galaxy, for a long long time......)

There are shells visible in your superb image, which are evidence of the accretion of smaller galaxies; it would seem that a remarkably large percentage of elliptical galaxies do have 'shells' in their envelopes, though they are always at very very very low contrast. Cannibalization of large numbers of small galaxies by big ellipticals is , these days, regarded as being virtually proven for big elliptical galaxies. (Maybe all big spheroidal galaxies have swallowed multiple small galaxies)

You have characterized the morphology of this galaxy very well, in your post:
As you have indicated, the "two component" structure of this galaxy image is typical of an S0 galaxy image.
The outer extremely-faint 'halo' has been modelled, in the literature, with an exponential radial falloff of light, which can be (though does not have to be!) the signature of an actual planar disk structure.

Thus, the apparent (on inspection) Hubble class of this galaxy is "very mild S0", and also, if we adopt the classification precepts of Allan Sandage in the Carnegie Atlas of galaxies, the mixed Hubble type E/S0
(= dominant spheroid, plus a very very very faint disk),
but the outer very-faint and very-extended structure may or may not actually be a real disk in three dimensions.

Hubble's original galaxy classification system only considered the structure of the two-dimensional image of an S0 or spiral galaxy, with a rapidly falling off component in the light (presumably a spheroid) and also a second component that has a more shallow falloff of light;
but more recent galaxy classification systems consider the various three-dimensional structures that each galaxy is composed of (this is an example of a physical classification system).

If the very outermost isophotes of this galaxy are somewhat blocky and rectilinear (= boxy) rather than slightly pointy (disky), then this is evidence that the very-extended outermost structure is not an actual disk structure.

Best regards,
Robert Lang

P.S.
In further cogitations, I am now wondering if the "shells" may or may not look more like arms.

[Shiraz]

that is a really beautiful image of a remarkable field Marco - extraordinary.

[madbadgalaxyman]

Oh, and one more comment....
Giant spheroid-dominated systems like IC 1459 often appear to be simple and featureless in many images, but deep and well-calibrated images like Marco's can reveal considerable complexity in these big elliptical galaxies and S0 galaxies.

Recent analyses in the literature have proved that these giant galaxies are - in reality - complex multi-component systems;
but it takes exceedingly accurate photometry and imaging, and analysis of stellar orbits and stellar populations, to show that these galaxies are composed of structurally and kinematically distinct sub-components.

cheers,
badgalaxyman

[marco]

Thanks all for the appreciation. Robert, your post is very informative, thanks for bring all these details to my knowledge. A real pleasure to read :thumbsup:

Clear skies
Marco

[madbadgalaxyman]

G'day Marco,
I am Glad you found the info interesting.

At some level, all elliptical galaxies are very individual, though the morphological features are always at extremely low contrast.

This giant early-type galaxy is not well studied , compared to its northern cousins; only a small handful of papers in the literature are devoted to it.
The only exception to this is that there have been a few papers about the distribution of mass near its centre and about the stellar orbits near to its very centre; presumably the signature of a giant black hole.

Professor Duncan Forbes (currently at Swinburne University) picked up some interesting features of the outer extremely-faint envelope of IC 1459 in this 1995 paper:
http://adsabs.harvard.edu/full/1995AJ....109.1576F
Unfortunately, the scans of these early papers in the ADS database are really bad, so it would be better to see the images in this paper in the original physical version of the 1995 Astronomical Journal.

I took the liberty of trying to stretch the .jpg version of your image, so as to better show the halo of this galaxy ( I hope you don't mind!):

162711

But I am sure that you can do much better than this with your raw data.

I am quite certain that the "shells" or "steps" in the envelope are real, though I am not so certain about the reality of the unusual luminous extensions that seem to stretch a long way out into the field.

Best regards
Robert

[nandopg]

Hi Marco,
The experience of hovering the full resolution image is fascinating ! I can tell you that this is the best image I've ever seen of the Grus's galaxy group. Galaxies shapes, colors, background... a perfection

Thank you very much for sharing.

Fernando

[atalas]

Nice field Marco.

[marco]

Thanks Louie and Fernando for the appreciation!
Regards
Marco

[marco]

Hi Robert, I don't mind at all :) Actually I am more than happy to send you a crop of the original fit unprocessed to you centered on the "shells" of IC1459 if you want to better analyzed it. I actually tried to do an extreme linear stretch on the reversed B&W luminance and I have to say that I get the impression that more than shell here we have extremely faint spiral arms.. It should be better take an image with a larger scope though to better see it..

In case you are interested just pm me..

Regards
Marco

[madbadgalaxyman]

Marco,

The surface brightness of the outermost features in IC 1459 is exceedingly low, so you have done very good work to show them even faintly. Your image of this galaxy is quite comparable to one that David Malin made with the UK Schmidt, and he had to stack several photographic plates to make his image.

Actually, "arm-like" features are sometimes found in elliptical-galaxy-like galaxies that have experienced merger with other galaxies (e.g. in NGC 1316.)
However, they usually look more like "ripples" or "waves" than actual spiral arms.....

Here are some examples:

(1) Messier 85 (this image from SDSS)
162781

(2) NGC 467 (which you imaged)

(3) NGC 2655 (Carnegie Atlas image)
162782

(4) NGC 2782 (SDSS image)
162783

(5) NGC 3205 (SDSS image)
162784

(6) NGC 7727
162785

The interest of some of these galaxies is that there is the possibility that an orthodox (usual appearance) disk and spiral arms could currently be in the process of formation.

See this interesting paper which makes the provocative hypothesis that NGC 1316 is actually a young Sombrero Galaxy in the process of formation:
http://adsabs.harvard.edu/abs/2012A%26A...539A..11M

This is a distinct and unique type of morphology which is not so rare amongst the bright galaxy population, and it is not on the ordinary Hubble sequence of galaxy morphologies.
(E - S0 - S0/a - Sa -Sb - Sc - Sd - Sdm - Sm - Irr)

[marco]

Thanks for this further note. Attached a crop on the galaxy, high stretch and inverted, no noise reduction nor other algorithms used to avoid to add any artifact, just a very strong nonlinear stretching..

I am not sure if what is out there is a system of shells or a kind of very faint spiral arms, definitely somebody with a much larger scope and deep exposure could get more details on that. After all I just used a 140mm lens at 1.83 "/pixels, too small to perform these studies..

Maybe it could be a good suggestion for somebody with a larger telescope next season this object gets high in the sky :)

Thanks again for the interesting exchange..

Clear Skies
Marco

[madbadgalaxyman]

Here are a few images of a "shell elliptical" galaxy, for comparison purposes.

Here is IC 4329, which is the brightest galaxy in the prominent and rich cluster of galaxies Abell 3574 :

162840

162838

162839

[astronobob]

Truly amaizing Marco, kinda reminds me of 'the hubble deep field'
Excellent to gaize apon & a major credit to your imaging ability :cool2:

[SkyViking]

Absolutely wonderful view Marco, well done! I love these deep galaxy vistas :D
The shell/arm structures may well be real, they are quite common for these types of galaxies.
The annotated image is great, I'll have to check that out in PI! :thumbsup:

[David Fitz-Henr]

Beautiful image Marco; I echo Rolf's sentiments about these deep galaxy fields, they provide such a sense of cosmic scale :thumbsup: