Paddy saith:
It is also amazing to read about the size of this system when the whole envelope is considered. I think it a bit ironic that the LMC is called a subdwarf when it is bigger than a dwarf. Wouldn't supradwarf fit better?
Bad Galaxy Man saith:
That was a typo on my part; Gerard de Vaucouleurs actually said LMC and similar galaxies are sub-giant galaxies!
Q. Is LMC a sub-giant galaxy or is it a super-dwarf galaxy?
In general,
low-luminosity star-forming galaxies (this definition excludes dwarf spheroidal/elliptical galaxies), have an
irregular structure, while star-forming galaxies which are similar in luminosity to the MW and M81 and M31 tend to have a reasonably regular spiral structure.
Based on the degree of regularity of its structure, I think LMC may simply be a regular Barred Spiral galaxy which has been somewhat perturbed.
((It is, in fact, possible to make a crude estimate of the luminosity of an unperturbed spiral galaxy, based on the degree of regularity of its spiral structure, which lead to the concept of a luminosity class for a spiral galaxy.))
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Ron!
Thanks very much for the pointer to the other thread on the LMC, I do appreciate it.
I should really check the literature to see if the imager in question has
really and truly picked up tidal material in his image.
Someone asks in this thread....... is the LMC really a spiral galaxy?;
There is one definite spiral arm at one end of its bar, and there is a short stub of an arm at the other end of its bar.
I think that LMC
is a spiral galaxy, as the spiral structure is somewhat evident in deep optical exposures, and very evident in the distribution of its cold atomic hydrogen gas (HI)
It seems plausible to me that LMC would be a lot more regular in appearance than it is, if it had not undergone one or more encounters with SMC and our own Galaxy.
LMC is often classified as the prototype of a galaxy-type called a "Magellanic Spiral". (it is
not classified as an irregular galaxy.)
The pioneering paper on this galaxy morphology was in the early 70s by our own Aussie extragalactic powerhouse Kenneth C Freeman and the great extragalactic astronomer Gerard de Vaucouleurs:
they concluded that a bar structure with one arm, or a bar structure with one arm and one arm stub, is a definite sign of a perturbed galaxy.
The following set of slides explains the definition of a Magellanic Spiral Galaxy (type SBm in the Hubble system) and some of the reasons that LMC is a
barred spiral galaxy:
http://www.ugr.es/~galaxybars2013/CarmeGallart.pdf
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