sillyworm 2 wrote: ↑Sun Oct 18, 2020 8:08 pm
Again..is the smaller galaxy in the arm of the larger galaxy mergings as well or is it behind the galaxy?
UGC 1810, the APOD of October 18, 2020.
Arp 273. NASA, ESA and Z. Levay
Sorry, I've been remiss. I should have said something about what is now yesterday's APOD, but I'm sorry to say I lost interest in it when I saw that it seemed to be a two-filter image. Also I knew that there is a relatively large galaxy interacting with UGC 1810 that was not visible in the APOD, and I just didn't feel like commenting.
But you are so right about the mini spiral in one of the arms of UGC 1810. It does look as if it is located squarely in one of the spiral arms of UGC 1810, and it does indeed look as if it is "interfering" with the star formation in this arm. Note how there are bright regions of star formation in the spiral arm "above" and "below" this mini spiral. Based on its appearance alone, I'd say that the mini spiral is indeed located in that arm of UGC 1810.
Also note the small quite red even tinier spiral(?) which seems to be plowing right through an arm of UGC 1810, leaving a wake behind it. But this tiny spiral is very red, casting doubt on its nature as a feature physically related to UGC 1810. It looks more like a redshift-reddened background object. The other "mini spiral" is the right color to be at the same distance from us as UGC 1810.
UGC 1810 is not the only spiral galaxy to contain a mini spiral galaxy located in one of its arms. The prime example of this feature is NGC 6050. NGC 6050 is actually a triple galaxy: There is one galaxy with extensive spiral arms and a large yellow bulge and center, one galaxy with extensive and very blue star forming spiral arms and a very faint bulge cut in half by a thin yellowish bar, and one much smaller barred spiral galaxy nested inside one large arm that seems to connect the two other galaxies.
The little galaxy nested inside the arm connecting the two other galaxies has a central bar that is just as bright as the thin bar of the larger galaxy that is all spiral fluff and little central substance.
So yes, I'd say that it is indeed possible for little spirals to be located inside arms of much larger spirals.
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