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ASTRO: A tangle of arms Arp 184
Arp 184, AKA NGC 1961 is almost too far north for me to image as it is
in my Polaris tree except for a few minutes each night. This image took me two months to get at 10 minutes a night. I missed some nights as my window of opportunity is only about 12 minutes long so I have to time things perfectly and to do that around other duties of the scope is not easy. Then it takes time to piece together 12 completely separate images taken at different temperatures and thus different image scale. This caused some elongation of stars at the left side of the image. When I started to put these pieces together I didn't have Registar. I should have gone back and started over once I got it but with hours of work already into it I didn't do that. It would have eliminated the elongated star problem but but increased the processing time. Arp 184 is about 180 million light years away and under Arp's classification of "Galaxies Classifiable as S(piral) or E(lliptical) with Narrow Filaments." In some cases these are long drawn out arms but in most I'm rather lost as to what these filaments are he is seeing. This is one of those cases. To me it should be classed as a spiral with really screwed up arms. The nice orderly pattern usually seen in spirals is missing with some arms drawn out and others apparently not even attached. Obviously it had to have reacted with something but none of the sources I found can name a candidate. While it looks like a merger in progress there's nothing it is merging with. It is one of 9 members of a small group of galaxies (the NGC 1961 group) packed into a sphere about 1 megaparsec in size (a parsec is 3.26 light years). One of these is CGCG 329-011 a distorted spiral to the left and a bit up of Arp 184. It looks like a one armed spiral, an Arp class, but it isn't a member of the class. Also it shows a lot of tidal debris on its east (left) side. Could the two have interacted in the past. It seems small to have caused this much havoc in Arp 184 but it may have lost a lot of its mass to Arp 184 thus accounting for the ring fragments. I found no discussion of this possibility in the literature however. Still CGCG 329-011 is very blue, even the core is somewhat blue. This would indicate something is triggering massive star formation in it. But it too has a nearby companion, [HR89] 053818+6923 to its left and down a bit. It too is blue so maybe those two interacted. The tidal debris on the east side would favor this view. Though with 9 galaxies in such close proximity all sorts of interactions are possible. Other members of the group are CGCG 329-009 an irregular spiral below Arp 184 with the splinter of a spiral, LEDA 138826, below and a bit left of it. In the lower left corner of the image is the Scd spiral UGC 03342. These other galaxies don't appear distorted however. Though they are seen near edge on which makes it hard to see if they are distorted when seen out of plane. Though such distortions usually do throw material out of the galaxies plane and that would be evident. In any case this is a rather interesting group of galaxies. Arp's photo with the 200" Palomar scope is at: http://nedwww.ipac.caltech.edu/level...ig_arp184.jpeg Rick -- Correct domain name is arvig and it is net not com. Prefix is correct. Third character is a zero rather than a capital "Oh". |
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ASTRO: A tangle of arms Arp 184
Sorry for the double posting. While sending the first time the news program locked up after I got a message the sending was unsuccessful. I closed the program and reopened it. Sure enough it wasn't at the news server so I sent it again. Then both copies were there. ARGH. Also I forgot the details. They aren't my usual so I better add them. 14" LX200R @ f/10, L=8x10', RGB=2x10', STL-11000XM, Paramount ME Note this had twice the normal lum data. I'd left a note saying some of the lum images were hurt by the Polaris tree causing some diffraction. Turned out it was very minor and when I used a sigma reject combine it wasn't seen at all. So I used all 8 though there was the temperature problem it didn't bother the main part of the image so I went with it. Rick |
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ASTRO: A tangle of arms Arp 184
Wow, that is one cool galaxy. Great image too.
Rick Johnson wrote: Sorry for the double posting. While sending the first time the news program locked up after I got a message the sending was unsuccessful. I closed the program and reopened it. Sure enough it wasn't at the news server so I sent it again. Then both copies were there. ARGH. Also I forgot the details. They aren't my usual so I better add them. 14" LX200R @ f/10, L=8x10', RGB=2x10', STL-11000XM, Paramount ME Note this had twice the normal lum data. I'd left a note saying some of the lum images were hurt by the Polaris tree causing some diffraction. Turned out it was very minor and when I used a sigma reject combine it wasn't seen at all. So I used all 8 though there was the temperature problem it didn't bother the main part of the image so I went with it. Rick -- Adriano 34°14'11.7"N |
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