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".

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

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