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ASTRO: The strange case of UGC 5600 and UGC 5609



 
 
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Old August 13th 14, 05:09 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Default ASTRO: The strange case of UGC 5600 and UGC 5609

UGC 5600 is a very strange, possibly polar ring galaxy in northern Draco
about 130 million light-years distant. It is classed as S0? by NED and
is surrounded by a faint ring. It also has a faint red linear feature
going east and west through its inner region that doesn't reach the
faint outer blue ring. I think this feature isn't real but an artifact
of my limited resolution blending in forground stars. There are two
main papers on this one and they don't agree. One says "This galaxy
shows optical emission in a large, diffuse face-on outer ring as well as
in the inner, narrow, and apparently edge-on ring that is perpendicular
to the position angle of the central object." That fits my description
of the faint outer ring and the linear red feature. But a later paper
says: "This system appears morphologically complex; it is interacting
with a close companion (UGC 5609) of similar size that lies only 1
arcmin (~14 kpc) away. Two other companions of similar redshift are
also nearby. Because of the interaction, it does not have a typical
polar-ring morphology. A thin extension, perhaps an edge-on inner ring,
appears in the north-south direction, while an outer ring, with the same
orientation but rounder (maybe less inclined with respect to the sky)
surrounds the galaxy." This says the two features are both oriented
north south. I see no such edge-on inner ring". Nor do I see it in the
SLOAN image. But then I don't see the east-west feature either! I'm
confused.

While both papers refer to UGC 5909 the later paper says there are two
other nearby galaxies with the same redshift as the UGC pair. The
second says there are none at NED which agrees with my check of NED. So
what are these two? one may be the galaxy to the northeast which is VII
Zw 323. A note for it says: "Probably associated with two blue
post-eruptive spirals..." then names the two UGC galaxies using a
different catalog designation. But I'm lost as to a 4th. There's only
one other galaxy with redshift data at NED and that is CGCG 350-047 but
it is 380 million light-years distant, three times further away. Look
for it in the lower right corner by a fairly bright orange star.

Oddly I find little on UGC 5609. It is a ring galaxy with the core
pushed to one side of the ring. This is almost always, maybe always,
caused by a dead on collision of a spiral with a dense small galaxy.
The effect is to push the spiral's core to the side of a ring this
creates. But the only mention of this I find is one that just says this
galaxy has an eccentric nucleus and nothing further. So where is the
galaxy that caused this mayhem? It seems nowhere to be found unless
somehow UGC 5600 did the deed. That might be the case. A third paper
says that UGC 5600 is forming a ring due to current accretion from a
companion. Adding that such galaxies are characterized by peculiar
velocity fields. It goes on to say: "The rotation curve along the major
axis of the galaxy is very peculiar, with counter-rotation in the
central (|r| 5") part. Rotation of the suspected ring is more regular:
to a first approximation, the observed radial velocities follow a
straight line ({sigma} = 17.6 km/s)." Note it makes no mention of this
being a polar ring nor of the second ring the other papers mention. Now
my head really hurts.

The papers can be found at:
http://adsabs.harvard.edu/cgi-bin/bi...J....107...99R
http://adsabs.harvard.edu/cgi-bin/bi...NRAS.284..773G
http://adsabs.harvard.edu/cgi-bin/bi...6A...291...57R
I've listed these in the order mentioned above.

With not much else on all the galaxies in the field I didn't make an
annotated image. While the DR9 SLOAN release does cover this field it
is yet to be picked up by NED.

Seeing was very poor for this image so it is rather soft. Yet another
of many that would benefit from a retake it likely won't get.

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

Rick
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Prefix is correct. Domain is arvig dot net

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