Quote:
Originally Posted by Argonavis
<quote>how can you be sure that the hydrogen is associated with Centaurus A and not foreground hydrogen in our galaxy?<quote>
That was my first question, but then I noticed a filament of ionized hydrogen extending from Cen a itself, then noticed that the immediate area around CentA appears to be clear, in fact it looks like CentA is surrounded by a bubble of Halpha, and the image is showing the densest parts visible through the sides of the bubble, whilst the foreground and background of the bubble is too faint to image.
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Thanks William! The morphology of the Ha certainly helps look like it could be associated with CenA -a large inner bubble and then spiral arms. I've attached an image from Hummels et al, ApJ 2019 showing a hydrodynamical model of the CGM in a 180kpc x 180kpc area (which would be a 3 x 3 angular degree area for Cen A) -this shows fairly similar streams and an inner ring 🤔:
https://www.iceinspace.com.au/forum/...1&d=1658179889
Interesting some of the absorption spectrum studies of the CGM have shown the amount of ionised gas increases as you move further away from the galaxy 😳
Cheers, Mat