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Old 11-05-2013, 11:29 AM
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madbadgalaxyman (Robert)
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Join Date: Mar 2011
Location: Brisbane
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Hi Steve,

Thank you for your characteristically detailed and interesting observations of N2442

It is hard to say, really, what three-dimensional morphological component the apparent bar actually is;
it could be a filled-in ring structure of some sort, or it could actually be a disk which is inclined to the line-of-sight. I have pondered this issue several times, but I can't seem to come to any conclusions!!

I suspect that the nucleus of which you speak in your observations probably corresponds to what would in previous days have been called a small bulge (= a spheroidal component composed mainly of old stars)

However, the bulge in this galaxy appears to be a pseudo-bulge, in that it looks like it has a disky (flattened) morphology; many barred-spirals do not have much of a real spheroidal bulge, instead having an inner mini-disk (which was formerly called a bulge)

Now I admit that this is cheating, but here is an HST closeup of the apparent bulge. Sure looks more like a disk!

Click image for larger version

Name:	N2442_(HST Legacy Archive data)(Processed by Rob Gendler_robgendlerastropics.com)_(2).jpg
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The morphological components within spiral galaxies are clearly and comprehensively described in this paper:
(Kormendy & Kennicutt, 2004, ARAA, 42, 603)

http://chandra.as.utexas.edu/~kormendy/ar3ss.html

This is very useful stuff, as it helps observers and theorists of all types, to come to a clear understanding of the known structures found within disk galaxies.

Best Regards,
Robert Lang
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