Is there a known or suspected cause for so much more star birth activity on one side/end of the LMC's "bar" as opposed to the other?
Actually, the LMC has more star formation on the other side of the bar (along
the bar) than we might think. Look at this image of LMC
by Robert Gendler. The second largest nebula in the LMC, after the Tarantula Nebula, is actually the nebular complex at 10 o'clock in the image. It isn't altogether easy to find out its name, although it may go by the designation NGC 1760
Clearly, most of the star formation of the LMC is on one side of the bar, as can be seen from Robert Gendler's picture. But some galaxies are just lopsided, for example NGC 5474
. NGC 5474 is affected by the strong tidal forces of giant galaxy M101
(which is in itself lopsided), and the LMC may well be affected both by its small "sibling", the SMC
, and by our own quite large galaxy, the Milky Way.
But in my opinion, it is even more interesting to try to understand the star formation in the Large Magellanic cloud by bearing in mind that it is a barred galaxy. It really has a very obvious and quite long bar. Is there a place in a barred galaxy where conditions are often particularly suitable for star formation? Actually, yes, there is, at the ends of the bar. Take a look at this watercolor painting of a barred spiral by Harriet Rex Smith
, and note the blue blobs of star formation at the ends of the bar. Reality is often like that, although there is usually more star formation at one end of the bar than at the other. A good example is M66
, where you can see that most of the bright red nebulas are at one end of the bar. NGC 5908
, on the other hand, has enhanced star formation on both sides of the bar, as does NGC 1530
. I find NGC 4450
very interesting. It has almost no star formation at all, except at the end of a dust lane which terminates at one end of the bar.
The way I understand it, a galactic bar tends to channel gas outwards, towards the ends of the bar. Here the gas runs into the more circular motion of the disk, and here we often find enhanced star formation. And that is how I think we should see the pattern of star formation in the LMC.