ASTRO: Arp 18 /NGC 4088

Arp 18 is cataloged as a spiral with a Detached Segment. Exactly how
this differs from the previous category above I'm not sure. More
commonly known as NGC 4088 this galaxy is 42 million light years away as
is its companion NGC 4085 at the bottom of the picture. Only 4088 has
the detached segment which I take to be the piece at the upper left.
Whether this is due to interaction with NGC 4085 I don't know. They
have the virtually the same radial velocity which is rarely the case
with interacting galaxies. Something disturbed NGC 4088 that's for sure.

The detached part of the galaxy carries a separate designation of SDSS
J120543.59+503319.0 ID and has a very different radial velocity. The
core of the galaxy is receding at 823 km/s relative to our galaxy but
the detached piece of an arm is moving away at only 661 km/s a
difference too great to be due to rotation of the galaxy alone. So
there's still a mystery here.

The barred spiral down and left (southeast) of ARP 18 is MCG +09-20-092.
It is surprisingly big and bright at magnitude 15.7 for a galaxy with
a red shift distance of about 750 million light years! It must be a
real giant of a galaxy if that distance is right.

14" LX200R @ f/10, L=6x10' binned 2x2 RGB=2x10' binned 3x3, STL-11000XM,
Paramount ME

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".