Two from Sculptor

[jase]

Hi All,

Plenty of great galaxy images on the forum being galaxy season. Here are two from the infamous Sculptor constellation.

IC5332 (http://cosmicphotos.com/gallery/image.php?fld_image_id=250&fld_album_id=12) - A lesser known spiral, this is believe to not be part of the Sculptor Group.

NGC300 (http://cosmicphotos.com/gallery/image.php?fld_image_id=251&fld_album_id=12) - The southern M33 needs no introduction.

Still getting the imaging rig dialled in but its starting to produce pleasing results.

Thanks for looking! :)

[multiweb]

Great to see you back up and running and what a come back. Two very cool shots. Heaps of details in those fields. :thumbsup::thumbsup::thumbsup:

[RickS]

A lovely pair of galaxies, Jase! Lots of small fuzzies showing some details as well.

[gregbradley]

Superb images Jase. IC5332 is another one of these beautiful but small southern galaxies.

Your NGC300 is divine.

Greg.

[jase]

Cheers Marc. Yes, I'm pleased to be back up and running, let me tell you. Processing is a little rusty but progress is being made.



Thanks Rick. Sure are plenty of small fuzzies on display. I procrastinated over the brightness of the background as a lighter background can emphasise such features but I'm not too keen on light backgrounds so kept it relatively dark. Some would say the background looks clipped but histograms are clean. Thanks for checking them out!



Cheers Greg. Pleased you liked them. There sure are many galaxies this time of the year, too many to image and do some justice on anyway.

[gregbradley]

On NGC300 there is that strange grouping of bright blue stars and a bright nebula right at the end of the top left hand spiral arm. It almost looks like a companion galaxy. You don't normally see that in a galaxy.

Robert may know something about that. Is it a companion galaxy?

Greg.

[peter_4059]

Great images Jase. Really like the way they have been processed.

[alpal]

Two great pics - well done.

[Peter Ward]

What's not too like?

Expertly captured at a long focal length and tack sharp. Beautifully processed.

Simply excellent :thumbsup::thumbsup:

[Larryp]

Lovely images!

[jase]

The structure is part of the same galaxy. The area you point out is a more vibrant region being less obscured by dust. This also explains why the HII knot is a deeper red. The other HII knots are reddish-pink due to the scattering a blue light from the young stars reflecting of dust. Similar phenomenon as M20 where the Ha area is pink due to the scattering of blue light. NGC300 is believed to be gravitationally bound by NGC55. I'm not aware of any possible companions in the immediate area.



Thanks Peter. Rusty processing have not worked on any images for the last three months. Workflow needs improvement, but it shouldn't take too long to get up to speed again.



Cheers Allan. Pleased you liked them.



Thanks Peter. A few more tweaks the set up will be humming. Guiding issues are now resolved but tracking could be improved. Just pleased to have something on the table at this stage. Thanks for the feedback.



Cheers Larry. Pleased you enjoyed them.

[Stevec35]

Nicely done Jase - I like them both. I imaged IC5332 a long time ago with the ST10. I probably ought to go back and try it again.

Cheers

Steve

[jase]

Cheers Steve. Would be good to see the 14.5" in action on IC5332. It's rather faint. In hindsight 30min lum subs would have been a better choice than the 20min lum subs used for the IC5332 image.

[RobF]

Yes, great to see you pulling in some photons again Jase. Processed to perfection as usual. Great stuff!

[Geoff45]

Both beautiful Jase. I especially like the core detail in 5332 and the Ha knots in ngc300
Geoff

[jase]

Thanks for appreciating the images, Rob. NGC300 is rather mainstream. I have a couple of long focal length mosaics which the system will probably start collecting data on early hours of the morning in a few weeks time. We'll see how they work out.



Cheers Geoff. IC5332 is a favourite that I've been wanting to image for sometime. The spiral structure leads all the way into the nucleus which I found fascinating. A true spiral in every sense of the word. Pleased you liked them.

[Bassnut]

Excellent to see you up and running Jase !. Very tight and sharp pics, I can see some other galaxys in both fields.

The weather has suddenly become atrocious since you started imaging, murphys law smacked you hard right there ;-)

[strongmanmike]

Ah don't ya just love galaxy season :clap:

Both lovely image Jase :thumbsup:

IC 5332 is indeed a faint bugger so you have captured it very nicely.

NGC 300 is excellent too, I like the highlighted HII as well (Greg probably doesn't though :lol:)

Looove all the background galaxies too :)

I notice odd star shapes in both images though :question: what is causing this do you recon?

Mike

[jase]

Thanks Fred. Wasn't smooth sailing with a few software glitches and guiding problems (two TSX bugs along the way which are now resolved with the latest build and PIR guiding angle related retrospectively). The system is nearly bedded down configuration wise to a point where its doing dusk and dawn flats automatically (when needed) and collecting around seven hours of data in between which isn't bad for this time of year with the short nights. TPoint model needs to be redone as one of the bugs impacted the accuracy. Was hoping to get that done this weekend but as you say, the weather has turned for the worse albeit completely unrelated to me starting to do any imaging :P



Thanks Mike. IC5332 is my pick of the two. I can't find many amateur images of this. Perhaps you can give it whirl. Interesting pick up on the star shapes. The flare around the stars don't agree with deconvolution which explains the odd shape. The raw subs are near perfect but a primary aperture mask would likely clean up the optical path further. There are a few other ways to address this with processing such as relayering the master as a star mask that is not passed through deconvolution which I may progress with in the next few images. Thanks for the feedback.

[strongmanmike]

I was going to shoot IC5332 actually but man, there are just sooo many cool galaxies to chose from this time of year :eyepop:

Hey I am not one to see a great image and only comment on the star shapes :rolleyes: and to me they don't stop either image from being visually very appealing :thumbsup: I was only asking because I noticed them and was a little surprised, that's all :) they look elongated virtically and slightly diamond shaped to me :shrug:

Mike

[Paul Haese]

Really like the NGC300. Nice going Jase.

[jase]

No drama Mike, you're not pissing on anyone's parade. Constructive feedback is welcome. I've just re-ran some of the data through the process again and confirmed deconvolution is the cause. One too many iterations by the looks. Am tempted to go back and fix it but I'm not going to for what its worth. The images are far from perfect and acquired during set up testing. Cheers



Thanks for checking them out Paul.

[Phil Hart]

Great to see Jase.. hope you're enjoying imaging again after a short siesta.

Phil

[Shiraz]

Really beautiful images Jase - fine detail and unobtrusive processing. top shelf. regards ray

[Rod771]

Fantastic images Jason :thumbsup:

Well done!

[astronobob]

Two lovely images Jason, quality proccessing, inspiring results :thumbsup:

[Octane]

The king has returned. :)

H

[tilbrook@rbe.ne]

Hi Jase,

There's no doubt about it, just a delight to look at!!!

As I've said before, we are spoiled on this forum with high end images you and others submit.

Cheers,

Justin.

[jase]

Thanks Phil. Yeah, it was a short siesta...I've not lost the zest for imaging.



Cheers Ray. Thanks for checking them out. NGC300 was acquired through its pass over the meridian so the quality of data was good to work with. Can't say the same for IC5332, yet it turned out ok.



Thanks Rod. Appreciated!



You're too kind Bob. Inspiring? Nah! Improvements can be made. Processing workflow needs some adjustment. More to come I hope.



Cheers H. Pleased you liked them. No king here, I'm the just the court jester clowning around, juggling RGB photons. :juggle:



Thanks Justin. Galaxy season sure is a treat, more so having a long focal length set up to chase them. Sure are many great images here of late.

====
Thanks again all. - Appreciated:)

[marc4darkskies]

Beautiful renditions Jase! I envy your SSO site!

Cheers, Marcus

[broca]

Nice work Jason. Very pleasing to the eye. Congrats!

[Ric]

Wonderful captures Jason.

I was wondering when we were going to see more of your work.

Cheers

[jase]

Thanks Marcus. Location is everything when it comes to long focal length work. Hope your site can handle it. I've still got my other remote site with an automated 2.3m dome that I'll likely set up a robotic wide field system at a later stage.



Cheers Steve. Pleased you liked them.



Thanks for checking them out, Ric. A small hiatus while I got the system set up and functional again, now getting back up to speed. More to follow soon.

[madbadgalaxyman]

Jason,

Yours is a remarkably good version of IC 5332…..it is much better than a lot of the science exposures I have seen of this galaxy (exposures that were made with much bigger telescopes.)

The survey images of this galaxy (e.g. image at the Carnegie-Irvine Galaxy Survey http://cgs.obs.carnegiescience.edu/CGS/Home.html) are invariably poor, because of its the low surface brightness;
in contrast, I feel that your image may well be the first ever image that really does this galaxy justice; it brings out the low-surface-brightness spiral arms which are barely visible or very faint in most other images of this galaxy…. these arms look bright enough in your image.

One remarkable fact about this galaxy is that while its two faint spiral arms are smooth and well-defined and very long , the distribution of its HII regions is entirely different;

the HII region distribution is rather chaotic and "scattered all over the place".

It is as if the old stars in this galaxy are arrayed in the traditional long-armed spiral structure , which is presumably caused by a density wave,
but in contrast, the youngest stars in this galaxy (= O & B stars)(= very luminous & hot Young stars which can ionize gas and make HII regions glow) , as can be traced by its HII regions, are currently forming in a completely different pattern.

IC 5332 really looks like quite a different galaxy if you consider its HII regions only.

Here are three different versions of the H-alpha image of this galaxy from the SINGG survey:
(in all cases, the stellar continuum has been subtracted out from the image, so these images essentially show nebular light only)


152021

152022

152023
The smooth and low-surface brightness Spiral Arms (that are seen in visible light and in infrared images) look like they have run out of puff, insofar as their production of young & luminous "eye candy"-type stars seems to have virtually ceased.
These long but smooth Spiral Arms actually resemble the smooth "fossil" spiral arms of the sort that were studied in Wray's color atlas of galaxies, in that star formation seems to be dying out in these arms.

Yet, in great contrast to the situation in these quiescent spiral arms, current (ongoing) star formation still seems to be very vigorous in the current H-alpha spiral arm pattern (as Ha emission is a superb tracer of the most recent star formation.)

All in all, IC 5332 is a much more unusual example of a modest luminosity Spiral Galaxy than is NGC 300 or M33 or NGC 7793

The appearance of IC 5332 is quite singular; this isn't just your average "subgiant" galaxy!
It is rare to have well-defined and narrow and long spiral arms in this type of underluminous galaxy, especially when these arms are in great contrast to the pattern of spiral structure which is seen in the young stellar population.

(Gerard de Vaucouleurs referred to subgiant galaxies as being those galaxies which are one or two magnitudes down in luminosity compared to the Milky Way and other luminous spiral galaxies. )
(For instance the apparent blue magnitude of IC 5332 is near 11, which implies that its blue absolute magnitude is minus 18.5 to minus 19.0))

The strong dichotomy between the old and the young spiral structure in this galaxy can be superbly illustrated by comparing your image of this galaxy with the following image from the GALEX satellite.
[ Essentially, the GALEX image is an image of only the youngest stars in this galaxy, as the GALEX ultraviolet band is mainly sensitive to the light of very luminous and newly-formed supergiant stars ]

I have taken the liberty (I hope you don’t mind!) of putting your image and the GALEX image in approximate registration, to show the remarkable contrast between the spiral structure of the old stars (as shown by the rather-yellow smooth arms in your image) and the semi-chaotic spiral structure of the young stars (as is shown in the GALEX image).

Here is the spiral structure of the old stars, as seen in your image, with Two long & well-defined & narrow & smooth arms which have a small opening angle:

152024

Here is the spiral structure of the young stars, as imaged by GALEX, with multiple short semi-chaotic arms having a larger opening angle:

152025

So IC 5332 doesn't even look like the same galaxy when only the young stars are emphasized.......

I find it fascinating that there can be two Very Different spiral patterns within a single galaxy!

I seem to recall some work by David Block that emphasized that there is a big difference between the behaviour of the young material in a galaxy (e.g. dense gas & dust clouds, molecular hydrogen clouds, HII regions, young stars) and the behaviour of the old material in a galaxy (which is mainly the old stars).
In the case of IC 5332, this difference is so great that one would say that the old stars and the newly-formed material (star forming regions, HII regions, OB stars) are decoupled and therefore display two different kinds of spiral structure.

To further emphasize my point, here is an image of IC 5332 from the Spitzer telescope and its IRAC instrument, displayed at a logarithmic scale. The wavelength of this image is 8 microns in the infrared:

152026
This Spitzer Telescope image emphasizes the relatively hot dust which is associated with regions of recent star formation, and the spiral pattern here is again much more open than the spiral pattern in the older stars.

[jase]

Robert,

Thank you kindly for such a detailed response. The advantage an amateur has over the professional is time. The array of off the shelf equipment coupled with time has its advantages. I blinked the aligned GALEX and Visible light images and was very surprised by the quantity of young star formations. It doesn't even look like the same galaxy with no strong signs of the spiral structure. I would have expected the old and new material to align or at best interact to some extent perhaps at a gravitational level to form a traditional spiral structure. This is certainly unexpected and very fascinating. I appreciate this additional insight.

[madbadgalaxyman]

Jase, here is some more commentary about your image!
cheers, Robert




GALEX satellite images (especially the Far-Ultraviolet images, with a bandpass near to 1500 Angstroms) are extremely responsive to the light from O & B stars, as the emission curve (black body curve) of these stars reaches its peak (maximum emission) at under 2000 Angstroms (so don’t go near to an O star or a B star…..rapid skin cancer would be the result!)
Therefore, even tiny faint blue knots of newly-formed stars that are extremely difficult to detect in images made at 5000 to 8000 Angstroms (500 to 800 nm) are extremely obvious in GALEX images.

It might be interesting to compare the H-alpha spiral structure of this galaxy (the observed distribution of is HII regions) with the Far-ultraviolet spiral structure that is displayed in the GALEX image. The FUV bandpass of the GALEX telescope detects a lot of light from very young stars (stars up to 10 million years old) but some of the light in these FUV images also comes from somewhat older stars (up to 600 million years old).

In contrast, the distribution of the HII regions in a galaxy provides a “snapshot” of the space distribution of only the youngest and most luminous stars. To make an HII region requires that the interstellar gas surrounding a star should first be bombarded with very-short-wavelength ultraviolet photons.
(it requires photons of wavelength < 912 Angstroms to split the atomic hydrogen of the interstellar medium into its constituent protons and electrons, and the recombination of these particles then produces the light that we detect coming from HII regions in the Balmer emission lines such as H-alpha 6563Angstroms and H-beta 4861Angstroms).
This ultraviolet light of <912 Angstroms wavelengths, which powers HII regions, can only be produced by the youngest (<= 10 million years) and most massive (>10 solar masses) stars, so the gentle glow of an HII region can only occur if there is at least one (or even more) of these young stars near to the nebula.
Because these young stars die out in a few million years, the HII regions that they energize also die out equally quickly!



In my view, there is noticeable, very open, spiral structure in the UV image (which shows the light from OB stars, and also the light from some A stars), and this structure is also seen in the H-alpha image. To me it seems that these are multiple spiral arms, but they are chaotic in appearance.

Spiral structure in under-luminous spiral galaxies is usually noticeably chaotic in appearance, and it often lacks that “oooh…..look at that pretty spiral!" type of strong two-armed symmetry .
[[
Example 1: for instance, NGC 300 has multiple low-contrast spiral arms. Though it also has a weak two-armed spiral pattern underlying this; so the human eye and brain do respond strongly to this underlying suggestion of symmetry.
Example 2: Here is a 3.6 micron (near-infrared) image of NGC 7793, taken with the Spitzer Telescope. As you can see, no obvious spiral structure; but perhaps just the merest suggestion of spiral arms.
152191

(this image is from the "S4G Atlas of Mid-Infrared Galaxy Morphology")

]]
So, in itself, there is nothing at all unusual about the multiple raggedy arms that are seen in IC 5332, in H-alpha and Ultraviolet images.

However, the simultaneous existence of a very well-defined and very symmetric underlying two-armed spiral structure in the old stars of a galaxy is an interesting phenomenon that has already attracted some attention from astrophysicists.

The spiral structure of the old material (=the old stars)(which comprise the dominant component of a galaxy’s mass) within the planar disk component of a galaxy is probably driven by very-large-scale slow-moving waves of increased density within the overall mass distribution of a galaxy, as per the density-wave theory of spiral arm formation. However, in IC 5332, this density wave does not seem to cause any evident star formation in the smooth arms with their small opening angle.

I am no authority on theories of spiral arm formation, but the alternative causative theory of "stochastic" or "propagating" star formation seems a lot more likely as an explanation for the origin of the semi-chaotic and much-more-open spiral pattern that is seen in the “Extreme Population I" material that recently formed in this galaxy (this mechanism of spiral arm formation involves a propagating 'chain reaction' of star formation...... with one knot of newly formed OB stars setting off another gas cloud to collapse, which then forms another knot of OB stars, which then cause another gas cloud to collapse, and so on.....)

So the Interstellar Medium of a galaxy can react on short time-scale to produce large numbers of regions of recent star formation and new stars;
in contrast, the old stars in a galaxy orbit about in a leisurely way, so the behaviour of the old material in a galaxy can diverge greatly from the behaviour of the young material.

In IC 5332, the current Very Prominent pattern of OB stars and HII regions may not last very long! Indeed, it is plausible that the currently observed spiral pattern (in this recently formed material) could completely disappear in a few million years time, when its massive young stars reach the ends of their lives.


This “decoupling” between old and young spiral structure has been remarked on before, in the literature (for instance, http://iopscience.iop.org/1538-3881/118/6/2618/fulltext/990219.text.html

[madbadgalaxyman]

Jason, This is my last post that is relevant to the appearance of your IC 5332 image.
Arguably, this discussion also belongs in the Science Forum. In fact, I will copy the posts on the dichotomy of spiral structure into the Science Forum so that the “science heavies” can consider them.

{{ Before I talk about science, I note that Gemini South Telescope recently released an image of this galaxy:
http://ausgo.aao.gov.au/contest2013/index.html
}}
"Gaseous young components of disks [a disk is the planar component of a spiral galaxy] (my italics) may be partially or even fully decoupled from the older disk population. As discussed by Block et al. (1994), the near-infrared spiral structure of galaxies often is quite regular and lacks multiple arms, indicating that higher-m modes of density waves are suppressed in the older stellar disk even if they are present in the younger component. The pitch angles (opening angles) of prominent near-infrared spiral structures may also differ from those of the optical spiral arms. "

- from D.M. Elmegreen et al., (1999), AJ, 118, 2618

The symmetrical two-armed structure in IC 5332 is remarkably obvious, though of low contrast.
In comparison, in many other galaxies which have (like IC 5332) a semi-chaotic structure of multiple knotty arms, a low-extinction near-infrared image is often necessary to "dig out" this spiral structure of the old stars, from the overlying dust and OB stars and HII regions and other young material.

A good explanation of the “duality” of the spiral patterns that can exist within a single galaxy, can be found in an article called “Shrouds of the Night – Galaxies and Rene Magritte” within the Conference Proceedings called “Galaxies and Their Masks : A Conference in honour of K.C. Freeman”
See google books, which enables access to part of this article:

http://books.google.com.au/books/about/Galaxies_and_their_Masks.html?id=PK 7MoOWD-F8C&redir_esc=y

(to find this article, search within the book for the title of this article, e.g. use the search terms “Shrouds of The Night”)
I quote here a few sections from this article by Freeman and Block and Puerari:
“Optically thick dusty domains in galaxy disks can completely camouflage or disguise underlying stellar structures. Cosmic dust grains act as masks or shrouds. (…….) Indeed the morphology of a spiral galaxy can completely change once the gaseous Population I disks of galaxies – the shrouds - are dust penetrated (…..)
From a dynamical viewpoint, the disk of a galaxy can be separated into two distinct components: the young gas-dominated Population I disk and the older star-dominated Population II disk "

In other words, two distinct components co-exist within the disk of a single spiral galaxy:


According to authors Kenneth C. Freeman and David L. Block and Ivanio Puerari , the gas-dominated young disk of HII & Interstellar Dust & Cold Atomic Hydrogen & Molecular Hydrogen and OB stars is active and responsive and fast-evolving, because it is characterized by small random motions (it is dynamically “cool”) and it is prone to the Jeans instability (gravitational contraction into dense gas clouds, and thereby into new stars).
In contrast with this young disk, these authors explain that there is also a distinct disk of “Population II” (= old) stars (which is the mass-dominant component a spiral galaxy), and that this old disk (and the spiral structure of old stars) may behave very differently from the young disk. This disk is dynamically warmer, and it has larger epicycles, and it evolves much more slowly than the young disk. The old stellar distribution in galaxies is sometimes touchingly referred to as the “stellar backbone of a galaxy”.
The morphologies of these two components of a spiral galaxy may be completely different from each other.

In earlier articles by some of these workers, for instance (http://articles.adsabs.harvard.edu//full/2001ASPC..230..137B/0000137.000.html) and (http://labs.adsabs.harvard.edu/adsabs/abs/1999A%26A...342..627B/) , it was shown that the multiple armed and knotty spiral pattern of a galaxy as viewed at blue and optical wavelengths , may be completely different from the much more regular spiral pattern that is observed in the distribution of its old stars ; In fact, a single spiral galaxy may have two very different Hubble types; an NIR Hubble type and an visible wavelengths Hubble type.
This contrasting “old stellar spiral” is often only revealed when an infrared image is made of a galaxy, so as to remove the overlying heavy dust distribution (which exists in some galaxies) and so as to make an image at a wavelength where more light is detected from the old stars within a galaxy.

(near-infrared light comes predominantly from red giant and red supergiant stars)
(The “old” spiral pattern in IC 5332 is mainly visible in the central part of this galaxy, probably because there is less confusion here with the dust and OB stars and HII regions that characterize the contrasting “young” spiral pattern)

[glenc]

Jase your images are always superb.

[jeff.d69]

WOW
Very beatiful images....
:jawdrop:

[jase]

Hi Robert,
Thanks for the supplemental information. I was not aware of the Gemini South image, WOW! I've thoroughly enjoyed reading through the detailed explanations and citations you have presented. It has allowed me to see the image from a completely different perspective. Thank you.



Cheers Glen. These were taken while during system set up and testing. Should be able to squeeze a little more from the system.


Thanks Jeff! Pleased you liked them.

[madbadgalaxyman]

Jase,

Your image was well worth a couple of days of analysis.
You imaging blokes struggle mightily to get your images, so it is only fair that someone looks for unusual structures in them!

Mine is undeniably the easier job;
after all, all I have to do to find really weird things in galaxies is to look at lots and lots and lots of galaxy images. On the other hand, those years that I spent comparing and contrasting many 10s of thousands of galaxy images , have given me a very keen eye for peculiarities and anomalies in galaxies!

While it is slightly disappointing to both of us that the "yin and yang"/dual/dichotomy spiral structure of galaxies is not actually a new discovery, the length and the small opening angle of the old stellar spiral is remarkable, as is the fact that both old and young structures can be seen without resorting to Near-infrared imaging of the sort I referred to in my analysis.

Best Regards,
Robert Lang

It is definitely true that your galaxy has no single unique Hubble type!!!
It actually has a contradictory Hubble type;
something like Sa/Sc

(actually, I need to have a more detailed look at how this galaxy should be classified!)

[astronobob]

Just looked through your web page Jason to find out what gear you have, wowsers, makes mine look like it was from Toyworld :o
Real nice Images by the way, M33 looks rather 3D too, :cool2:

[jase]

Thanks Robert. I'd be interested to know the final classification given the galaxy's complex nature once more information comes to hand.



"Once you start down the dark path, forever will it dominate your destiny, consume you it will." - Yoda
A concise statement but captures the essence of astro imaging. Addictive and consuming. Personally, I'm not interested in the gear. Its just a means to getting data. I get more pleasure out of processing. Each to their own I guess. :)

[madbadgalaxyman]

I would like to send a link to your I5332 image, to Professor Ron Buta (Univ. of Alabama), who is a leading authority on galaxy classification.
(the Science Forum contains a link to his recent comprehensive review of galaxy morphology)
But it is hard to know if there would be enough interest among the "pros" to make a serious study of this galaxy. Its morphology is distinctive, but not absolutely unique.

One probably shouldn't get too obsessed with assigning a single Hubble class/type to each galaxy, as so many specific galaxies do not exactly correspond to a specific Hubble type.(for instance, there exist smooth-armed spiral galaxies that have a small bulge)

Hubble classes are essentially a convenient shorthand for describing, in a rough and ready way, what sort of galaxy we are talking about. However, within each Hubble type, there is a very large range of galaxy morphologies.

IC 5332 is in fact a good example of a galaxy that cannot readily be assigned a single unique type within the orthodox Hubble Sequence
(E - S0 - S0/a - Sa - Sb - Sc - Scd - Sd - Sm - Irr)

The inner spiral structure (quiescent ; yellow ; smooth ; two-armed) would in fact be more typical of an Sa galaxy.
In contrast, the more outer spiral structure (strongly star-forming ; blue ; entropic ; multiple-armed) corresponds much more to that which you would find in a galaxy that is later in the Hubble Sequence, perhaps a galaxy of type Sd.

So the template of a single Hubble class (type) is not very useful in the case of this galaxy;
it is a case of "either this type, or that type, or, more properly, both types".
Strange, but true!
As Obi Wan Kenobi said "these are the truths that we must cling to, Luke".

cheers, Mad Galaxy Man