[madbadgalaxyman (Robert)]

Originally Posted by multiweb

The IR version is an eye opener. I never noticed it was a barred spiral not unlike the one face on in Fornax.

Marc

In optical imagery, and also in visual observation, there is the suggestion of a bar in NGC 253, but when I compared the so-called 'bar' seen at visual wavelengths to the actual bar that is plainly seen longward of 1 microns, I found that the bar seen in visual imagery and observations is not the real bar; the visual "bar" is a sort of "cutout" made of residual light that is surrounded by highly obscured areas.

It is extremely tough to figure out the actual structure of a galaxy like this, which is not far from being in an edge-on orientation, as all of the structure is foreshortened and compressed (the NGC 4945 case is even harder to figure out than NGC 253!). I am not up on the most recent estimates of the inclination of NGC 253, but some of the older literature gave values of 10-18 degrees from edge-on.

The "traditional" hubble class assignment of this galaxy, which is traditionally estimated from blue or visual imagery, is actually Sc [ or perhaps S(B)c ], but it is the very dusty nature of the images at these wavelengths that gives this galaxy the appearance of having large star-forming knots as are commonly seen in an Sc galaxy.
(The HII regions look quite small, so the Sc type is, in my view, highly questionable)

However, the near-infrared Hubble Type is probably earlier in the Hubble Sequence; SBbc or SBb

cheers,
bad galaxy man

Added in edit:
For fun and profit, here is another version of the NIR image, emphasizing the dust distribution:



And here is a negative version of a very high quality LRGB taken with a 24 inch RC at the Mt Lemmon SkyCenter by Adam Block. The heavy dust distribution all over the face of this galaxy is particularly obvious in this negative.