ASTRO: Arp 224 Two tails of a merger

Arp 224, NGC 3921, is considered to be a merger in progress.
Simulations indicate it is about 0.5 to 0.8 billion years since the
merger began. It is part of a cluster of galaxies about 275 million
light-years distant and is in the bowl of the Big Dipper not far from
Phecda (Gamma Ursae Majoris). Arp included it under Galaxies (not
classifiable as S or E): amorphous spiral arms. Though a note in NED
incorrectly says it us under the preceding category, adjacent loops.
Arp's comment: "Straight filament leads to bright offset nucleus." Yet
his image shows it to be slightly curved. The CGCG catalog notes: "Blue
disk-like post-eruptive compact with large external loop and extended
jets." I would imagine given another billion years or so those stars
will settle back into the galaxy creating a large elliptical galaxy.
For now it appears one galaxy left the huge looping tail while the other
left the shorter and weaker slightly curved tail. I see only one well
defined core. Since the smaller tail appears to connect to it I'll go
out on a limb and say it is the source of that tail. Could it be it
being more massive pretty well tore up the other less massive one
creating the huge looping plume ending in what appear to be a bunch of
small "cores" arcing north of the main core. Is that all that's left of
its core or is that hidden behind the other one? I'm only guessing here.

Directly west of Arp 224 is SDSS J115059.24+550413.5 looking like a
dwarf spiral and below it is SDSS J115059.33+550310.0 an even smaller
dwarf elliptical. Both are at about he same distance as Arp 224. Also
a member of the group is NGC 3916, the SAb spiral to the northwest of
Arp 224 as is the smaller spiral to the SW that appears to harbor a
"Saturn" like core in my shot. It is MCG +09-19-213.

The galaxy cluster ZwCl 1148.6+5523 is just about centered on Arp 224.
It is said to have about 121 members and is about 50' across, far larger
than my image.

The galaxies in this image seem to fall into several distance
categories. The Arp 224 group being the closest. Then there's a group
at about 775 through 820 million light years. A typical member is the
round galaxy southwest of MCG +09-19-213.

Another group is at 1 billion light years and seems to be likely the
group referred to in the Zwicky cluster. It is centered on the giant
red elliptical galaxy a short distance northeast of Arp 224. The Zwicky
cluster's center is about half way between it and Arp 224. Most of the
obviously orange galaxies around this area appear part of this group.

Then there's a scattering of even more distant galaxies, such as SDSS
J115036.68+550915.0, the star-like very orange galaxy west north west of
NGC 3916. It appears brighter than its rated 18.8 magnitude and far
more distant than you expect at 2.7 billion light years.

Annotated image shows distance to non Arp 224 group galaxies when known.
All galaxies showing detail but without a distance shown are members
of the Arp 224 group at about 275 million light-years.

Arp's image:
http://nedwww.ipac.caltech.edu/level...ig_arp224.jpeg
SDSS image:
http://astronomerica.awardspace.com/SDSS-29/NGC3921.php
Hubble Space Telescope -- core
http://hubblesite.org/newscenter/arc...97/34/image/v/
Hubble Space Telescope -- southern half of Arp 224
http://hubblesite.org/newscenter/arc.../x/format/web/

Sorry, I couldn't find any larger versions of the Hubble images, the
data in the archive wasn't complete enough from what I saw to make a
larger version.

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

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".

Another good one Rick. It (or they) looks really warped.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
. com...
Arp 224, NGC 3921, is considered to be a merger in progress.
Simulations indicate it is about 0.5 to 0.8 billion years since the
merger began. It is part of a cluster of galaxies about 275 million
light-years distant and is in the bowl of the Big Dipper not far from
Phecda (Gamma Ursae Majoris). Arp included it under Galaxies (not
classifiable as S or E): amorphous spiral arms. Though a note in NED
incorrectly says it us under the preceding category, adjacent loops.
Arp's comment: "Straight filament leads to bright offset nucleus." Yet
his image shows it to be slightly curved. The CGCG catalog notes: "Blue
disk-like post-eruptive compact with large external loop and extended
jets." I would imagine given another billion years or so those stars
will settle back into the galaxy creating a large elliptical galaxy.
For now it appears one galaxy left the huge looping tail while the other
left the shorter and weaker slightly curved tail. I see only one well
defined core. Since the smaller tail appears to connect to it I'll go
out on a limb and say it is the source of that tail. Could it be it
being more massive pretty well tore up the other less massive one
creating the huge looping plume ending in what appear to be a bunch of
small "cores" arcing north of the main core. Is that all that's left of
its core or is that hidden behind the other one? I'm only guessing here.

Directly west of Arp 224 is SDSS J115059.24+550413.5 looking like a
dwarf spiral and below it is SDSS J115059.33+550310.0 an even smaller
dwarf elliptical. Both are at about he same distance as Arp 224. Also
a member of the group is NGC 3916, the SAb spiral to the northwest of
Arp 224 as is the smaller spiral to the SW that appears to harbor a
"Saturn" like core in my shot. It is MCG +09-19-213.

The galaxy cluster ZwCl 1148.6+5523 is just about centered on Arp 224.
It is said to have about 121 members and is about 50' across, far larger
than my image.

The galaxies in this image seem to fall into several distance
categories. The Arp 224 group being the closest. Then there's a group
at about 775 through 820 million light years. A typical member is the
round galaxy southwest of MCG +09-19-213.

Another group is at 1 billion light years and seems to be likely the
group referred to in the Zwicky cluster. It is centered on the giant
red elliptical galaxy a short distance northeast of Arp 224. The Zwicky
cluster's center is about half way between it and Arp 224. Most of the
obviously orange galaxies around this area appear part of this group.

Then there's a scattering of even more distant galaxies, such as SDSS
J115036.68+550915.0, the star-like very orange galaxy west north west of
NGC 3916. It appears brighter than its rated 18.8 magnitude and far
more distant than you expect at 2.7 billion light years.

Annotated image shows distance to non Arp 224 group galaxies when known.
All galaxies showing detail but without a distance shown are members
of the Arp 224 group at about 275 million light-years.

Arp's image:
http://nedwww.ipac.caltech.edu/level...ig_arp224.jpeg
SDSS image:
http://astronomerica.awardspace.com/SDSS-29/NGC3921.php
Hubble Space Telescope -- core
http://hubblesite.org/newscenter/arc...97/34/image/v/
Hubble Space Telescope -- southern half of Arp 224
http://hubblesite.org/newscenter/arc.../x/format/web/

Sorry, I couldn't find any larger versions of the Hubble images, the
data in the archive wasn't complete enough from what I saw to make a
larger version.

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

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".