Quote:
Originally Posted by RickS
I have tried to make the IFN (Integrated Flux Nebula) the main feature of the image for better or worse 
Rick. |
Very beautiful, Rick.
In addition to the IFN, existing in this field is also quite a lot of tidal material which has been drawn out of some of the galaxies by interactions between them. For instance, in this Ultraviolet image from GALEX, you can see some knots of OB stars which are a long way from M81. I have seen these blue knots, though very faintly, in some Very Deep amateur images made with standard CCDs:
The difficulty of finding faint extensions of the galaxies in this field, in the optical regime, must surely be to distinguish genuine features from the IFN.
Have you or any of your imaging colleagues any way of subtracting out the IFN from images? It would have to be accurately subtracted from an image in order to leave only those features which are at the distance of M81/M82...... as a residual image.
In this thread, SamD has found a nice 12 micron image of the field, which may facilitate in subtracting out the foreground nebulosity; in order to isolate only the tidal material between the galaxies.
___________________________________ _
Quote:
Originally Posted by Placidus
You've just convinced me that there really is such a thing as interstellar medium, even far from the Milky Way, and it isn't just artifact of processing..
|
It sure exists.....just take the same star cluster with the same mix of stellar spectral classifications and put it a couple of thousand light years away; then it looks perceptibly redder due to effects of submicron-sized dust particles that permeate all the space between the stars.
But it took a long time for astronomers to become convinced of the existence of a diffuse medium of dust that relatively evenly permeates our own Galaxy. Here is the first of the two 1930 discovery papers by
Robert Trumpler:
http://articles.adsabs.harvard.edu/f...ASP...42..214T
Here is a good overview of much of the early work on dust in our galaxy:
http://articles.adsabs.harvard.edu//...00310.000.html
Another thing that exists between the stars of spiral galaxies is a faint diffuse H-alpha nebulosity.... which is simply gas that has been caused to gently glow by the radiation field of a galaxy. Some amateur Ha images are deep enough to detect the diffuse H-alpha emission between the stars, e.g. this one by Mike Sidonio:
http://www.iceinspace.com.au/forum/s...t=91067&page=2
Those galaxies with a large population of young blue massive stars can have prominent H-alpha emitting nebulosity throughout the entire galaxy, for instance here is an H-alpha image of NGC 4945;
____________________
____________________