Quote:
Originally Posted by strongmanmike
Yes I was intrigued by the stars/dust/halo structure component of this cluster too and how much is Milky Way Cirrus and how much is actually the big elliptical which appears to stretch right across the cluster..?
Mike |
Thanks for displaying the high-contrast version of your image. The vast "halo" of this galaxy looks quite obvious here.
I think that the ultra-faint luminous extensions of the big elliptical are
not cirrus. That's my opinion, anyway.
They don't look like cirrus to me, in fact they look more like a component of IC 4765 itself.
The
surface brightness, and the
falloff of light with increasing galactocentric radius, and the
distribution, of this light seems to be distinct from that of the cirrus that is in this field.
It is pretty cool to see this galaxy extending so far across the cluster!
This appearance is not necessarily unusual for those galaxies that are dominant in their clusters, but it is generally very hard to actually get decent images of this vanishingly faint light stretching between the galaxies of a cluster.....
so all credit to you, Mike.
The velocities of the stars that are responsible for the ultra-faint diffuse light can be used to separate out those stars belonging to the galaxy and those stars belonging to the cluster; there is no other way of doing this.
It is normal to try to get spectra of planetary nebulae in the diffuse ultra-faint light, in order to figure out the velocities of stars in our line-of-sight.
(this requires a "beeeeg" telescope)
Here's one of my all-time favourite images, showing the ultra-faint inter-galaxy light in the Virgo Cluster.
I think I may have shown this one to you before, but perhaps some of the other IIS members would also benefit from thinking about this very weird image:
