Spiral vs elliptical
-
by
v3nom
How to classify such galaxy? In my opinion it does not look like elliptical are they are often yellow, but there are not enough details to classify it as a spiral. Is it fair enough to select "elliptical" or better go "disk or features -> no edge-on, no bar, no spiral'?
Posted
-
by
JeanTate
It really depends, IMHO, on how much 'external' info you want to bring.
For example, detailed studies of ETGs ("early type galaxies", i.e. ellipticals and lenticulars) show that there are no "E8" or "E9" (etc) ellipticals ... the "E" stands for elliptical, and the number is the 'ellipticity', which in this case is defined as ten times (1 -b/a), where b/a is the minor/major axis (length) ratio (and in Ron Buta's masterwork - Galaxy Morphology - he reports that even E7s are actually disk galaxies).
So, in this case, the galaxy is too elongated, too cigar-shaped, to be an elliptical. But there is no separate class 'lenticular'; what to do? Perhaps the smooth -> cigar shaped decision tree was designed, by the Zooniverse/GZ Science Team, to capture just this? Perhaps, by explicitly writing features' they intended us zooites to choose 'smooth' for objects like this?
In the end I think it is unlikely to matter, if only because some zooites will choose the 'smooth -> cigar-shaped' limb, and others the 'disk -> not edge-on/no bar/no spiral pattern' limb, so its morphological characteristics will be captured well.
Posted
-
by
ElisabethB
moderator
You could go for smooth - cigar shaped or you could go for an edge on or ....
Just answer the questions as well as you can.
Happy hunting ! 😄
Posted
-
by
v3nom
Thank you guys (and girls) for response. JeanTate, I think you have already elaborated this topic somewhere else. PDF is pretty long, but full of pictures, so definitely I will go trough it 😉
In meantime I found this link with "SINGS Hubble Tuning Fork Poster" (large posters):
http://sings.stsci.edu/Publications/sings_poster.htmlIt is very useful!
Posted