ASTRO: Arp 182

The spike of Arp 192 turned out to be a false alarm and was only an
asteroid. But Arp 182 has an even longer and almost as narrow of a
spike that too is virtually straight and darned hard to explain. It
also looks artificial and unreal but this one does really exist.

Arp 182 is also known as Hickson 96. It is a tight group of 4 galaxies
about 375 million light years away. The main one is NGC 7674, Hickson
96A, classed as SA(r)bcP. It is interacting with NGC 7674A or Hickson
96C. The result is a rather normal small plume to the north with a
detached (in my image that is) plume further north. The really strange
one is the narrow, well defined one heading in a near straight line to
the east northeast. While it barely shows on Arp's image I didn't see
it before my image started to come in. After the first frame I was sure
I had a reflection. I moved it on the sensor but the "reflection" moved
like a real object so I went back to my original position and finished
the shoot figuring I'd just deal with it in processing. It looked too
real when I got around to processing it over 6 months later. It was
taken last August. A bit of research was called for, looking at Arp's
notes, in this case, turned up the fact he had noticed it. His comment:
"Long straight, very faint filament like bow wave from companion." Also
I should have noticed his classification under Galaxies: Narrow
filaments. I just thought he meant the stuff on the north side. Hubble
has taken a great image of this galaxy. It is oriented with east down
rather than to the left as my image is. Oddly the filament is dimmer on
that image than mine yet his's shows the filament I see as detached as
connected to the galaxy. I don't know why the difference other than it
may be due to my far lower resolution. In fact it appears the
"detached" filament is really an extension of the outer arm much like in
the Whirlpool Galaxy, M51, Arp 85. It's the short one tucked in between
it and the galaxy that may be harder to eplain. Is it part of the other
arm? How the long straight eastward filament fits in I just don't know.
It does appear to curve into the companion which has a tidal plume at
the other end. Problem is the plume is somewhat blue and the other
plume is rather red. While the companion has some gas and dust was it
enough to trigger such massive star formation in the plume? Apparently
it was.
Hubble's image: http://www.spacetelescope.org/images...eic0810bp.html

The third member of the group shows in the Hubble image with some
detail. In mine it is just a small blue oval to the left of NGC 7674.
It is Hickson 96D or PGC 71507. The 4th member doesn't fit in the
Hubble image frame. It is further east, left, and is NGC 7475, Hickson
96B. Most sources say it is an SAB(s)0 galaxy. NED agrees one place
and another says it is E2. It sure has the color of an elliptical
galaxy. S0 galaxies usually are white to slightly orange in color.

There's little information on the other galaxies in this area. 2MASX
J23274259+0845298 to the west south west is also at about the same
distance and thus likely a member of the group just not close enough
that Hickson included it. The odd spiral directly above NGC 7674, near
the top edge of my image, that appears to have but one spiral arm in a
otherwise amorphous disk is CGCG 406-113. It is a bit further away at
nearly 550 million lightyears. The oval ring galaxy to the southwest is
2MASX J23273713+0841028. I have no distance data. The bright galaxy in
the upper left corner is CGCG 406-117, a spiral that also appears to be
part of the same group as it too is located at about the same distance.

The edge on spiral at the right edge in the center is CGCG 406-109. It
is only 260 million light years away so probably not related. The
galaxy at the very bottom center edge is 2MASX J23275583+0835513. I
have little on it. It appears to be another ring galaxy, round this
time. Unfortunately, this field is out of the SDSS survey area so most
galaxies are uncataloged. There's an interesting pair of small very
blue apparently interacting galaxies NW of Arp 182. Unfortunately, like
most in this image they are uncataloged. A similar pair is to the right
of the oval ring galaxy 2MASX J23273713+0841028 half way to the edge.
There's also an Xray galaxy in the image, HELLAS 209. Start from the
blue pair of possibly interacting galaxies mentioned above and go to the
southwest (lower right). You will come to a slightly fuzzy star. It
makes an isosoles triangle with the star blow the galaxy pair. It is
HELLAS 209 some 1.9 billion light years distant.

The image contains three asteroids. The brightest to the south east of
center is 1999 UP47 at an estimated magnitude of 18.2. Much fainter to
the southwest of center not far from the bottom half way from the center
to the right edge is 2005 TF1 at magnitude 19.3. The lack of a number
indicates it hasn't yet been observered long enough to make one trip
around the sun. The third is a bit brighter and is east and a tad north
of NGC 7675. This is now my 3rd unknown asteroid. I really do need to
check these for unknown asteroids ASAP rather than 6 to 9 months later.
It will stay undiscovered for a while longer it appears.

Arp's image:
http://nedwww.ipac.caltech.edu/level...ig_arp182.jpeg

14"LX200R @ f/10, L=4x10 RGB=2x10x3, STL-11000XM, Paramount ME

Besides the full image I've included a crop at 150%.

Rick

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Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".