Where is the boundary of a galaxy?
Just realized this question ... when classifying a galaxy like the above, where is the boundary? Does it included the purple,green, etc. dots surrounding the central object? Are these considered as tidal debris?
Also, the squares growing outward, are they the Airy pattern?
by ElisabethB moderator
Mmmm ! I thought I had posted an answer to this but I cannot seem to find it. Must have hit the wrong button !
Anyway, here it is : I see a barred spiral with two fuzzy arms. The coloured dots and squares are just noise (artifacts).
Just try squinting and the barred spiral becomes a lot clearer !
Happy hunting ! 😄
when classifying a galaxy like the above, where is the boundary?
It's as far out as you think you can see something that you consider to be part of the galaxy. Like GZ in general, use your best judgement.
Does it included the purple,green, etc. dots surrounding the central object?
I would say yes.
Are these considered as tidal debris?
Myself, I'd say no. I think they form a somewhat lopsided, rather diffuse ring (actually an ellipse). This kind of outer ring, on a barred spiral, is not all that unusual, but they aren't always so easy to see.
Hope this helps, and happy hunting! 😃
Thanks a million! 😄