View Single Post
  #5  
Old 08-01-2013, 03:36 PM
madbadgalaxyman's Avatar
madbadgalaxyman (Robert)
Registered User

madbadgalaxyman is offline
 
Join Date: Mar 2011
Location: Brisbane
Posts: 936
Hi Russell,

I am very happy with your image of NGC 1300.....short exposures are great!!

Often, the most interesting parts of galaxies are their centralmost parts, and these parts can be well and truly burnt out on long exposures.

Your image clearly shows a feature of NGC 1300 which is not so easily seen on the typical long exposure of this galaxy with a CCD camera.....the central ring of supergiant star forming regions.

Here is the tight innermost ring in NGC 1300, in an exposure with the VLT (used with the EFOSC2 instrument):

Click image for larger version

Name:	N1300_w.EFOSC2_(at ESO).jpg
Views:	23
Size:	182.8 KB
ID:	129855

Here is a low resolution version of a Hubble Space Telescope image (taken with the F435W filter)(similar to a blue-sensitive Johnson "B" photometric filter) showing this innermost ring of young bright stars and clusters:

Click image for larger version

Name:	N1300___B band (F435W)_w.HST_(Hubble Heritage).jpg
Views:	18
Size:	163.2 KB
ID:	129856
___________________________

In fact, it is the shortness of your exposures that makes this central feature stand out so very much!

I forget how large, in angular terms, this small central ring is, but it seems to me it might be observable visually.

cheers
bad galaxy man

The tight rings immediately surrounding the central starlike nuclei of galaxies are sometimes known, "in the trade", as "circumnuclear starbursts or "circumnuclear starburst rings. ("nuclear rings" is another way they are known.)

Ring structures often occur at various spatial scales, and a single galaxy can have several different rings within it;
for instance, the two main spiral arms of NGC 1300, when traced out a long way (to very faint levels), curve around to form a ring structure (a nearly complete ring).

Ring structures in galaxies were described by Buta and Combes, in Fund. Cosmic Physics, 1996, vol. 17, p.95;

http://ned.ipac.caltech.edu/level5/Rings/paper.pdf

Another useful guide to the variety of ring phenomena is the "De Vaucouleurs Atlas of Galaxies"

Last edited by madbadgalaxyman; 08-01-2013 at 03:57 PM. Reason: more
Reply With Quote