ASTRO: Arp 68 with a weird arm

Arp 68/NGC 7756 is a Sc spiral galaxy in Pisces at about 120 million
light-years. Arp included it in his category Sprial Galaxies with small
high surface brightness companions on arms. I'd have put it in his
heavy arm category as the "companion" appears to be in the distant
background. Arp said the companion was NGC 7756. Lord Rosse who
discovered NGC 7756 and NGC 7757 said this about NGC 7756 "Another neb
about 5' sp (NGC 7757)." By "sp" he means south preceeding which is
south west. The only object 5' south west of NGC 7757 is a 12.8
magnitude rather white star. His description is a a match for NGC 7757.
No one doubts this is a double sighting of NGC 7757. The problem is
some sources, like Arp, claim the companion is NGC 7756. This obviously
isn't the case. The Kanipe-Webb book gets it right as does NED and the
NGC Project. But what is the designation of the companion? It doesn't
seem to have one, at least in NED! NED does list an HII region within a
couple seconds of arc of its position however. I can't see it against
the distant galaxy. In fact most of the fuzzy objects in my image don't
have any catalog entry that NED shows. Within 15' radius of Arp 68 NED
lists only 6 other galaxies, one one of which has a red shift listed.
You'll find this galaxy due east (left) of Arp 68 just above a rather
bright star. It is the X-ray galaxy GALEX 2690243303817875752 also at
120 million light-years. The very blue galaxy just below Arp 68 and a
tad to the east of its center is [HDL96] 407-017. I have nothing much
on it.

Most sources consider the companion just a coincidence of line of sight
that isn't related to Arp 68 in any way. It shows no sign of
interaction though NGC 7757 does seem somewhat disturbed. Arp noted the
arm saying "Many star-like knots lined up along straight arm." If it
has interacted with anything recently the only candidate appears to be
the other one at 120 million light years. Being an X-ray galaxy it has
apparently been fired up. But there's no real evidence the two ever
interacted. A better candidate might be be NGC 7750 about 39 minutes
southwest of Arp 68 so well out of my image. It also is about 120
million light years distant and is classed as (R')SB(rs)c pec:. They
are too far apart for one frame but I wish I'd realized it was there
last fall. I'll try for it this fall weather willing.

The image has quite a few asteroids in it. What's really annoying to me
is that THREE of them are unknown to the Minor Planet Center.
Unfortunately, I took this back last September and just recently found
the asteroids so there's no way to follow up. They are still lost
awaiting discovery it seems. I've "found" about 8 now that I've seen
months too late to follow up on. This is getting to be routine with me
it seems. I've included an annotated image that shows that identifies
the asteroids.

(91197) 1998 SD115 magnitude 18.3
2002 PY124 magnitude 19.2
2005 SZ152 magnitude 19.7
3 unknowns

This field is out of the Sloan survey area so there's very little data
available and no professional images, other than Arp's, that I could
find on the net.

Arp's image
http://nedwww.ipac.caltech.edu/level...big_arp68.jpeg
His image appears to have a plate defect at the southwest end of the
companion (right in his photo). It appears to be a round stain of some
sort.

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".

Forgot exposure data:

14" LX200R @ f/10, L=4x10' RGB=2x10'x3, 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".

Added to my list to image.

I love those Pec galaxies.


On Sun, 18 Jul 2010 01:05:09 -0500, Rick Johnson
wrote:

Arp 68/NGC 7756 is a Sc spiral galaxy in Pisces at about 120 million
light-years. Arp included it in his category Sprial Galaxies with small
high surface brightness companions on arms. I'd have put it in his
heavy arm category as the "companion" appears to be in the distant
background. Arp said the companion was NGC 7756. Lord Rosse who
discovered NGC 7756 and NGC 7757 said this about NGC 7756 "Another neb
about 5' sp (NGC 7757)." By "sp" he means south preceeding which is
south west. The only object 5' south west of NGC 7757 is a 12.8
magnitude rather white star. His description is a a match for NGC 7757.
No one doubts this is a double sighting of NGC 7757. The problem is
some sources, like Arp, claim the companion is NGC 7756. This obviously
isn't the case. The Kanipe-Webb book gets it right as does NED and the
NGC Project. But what is the designation of the companion? It doesn't
seem to have one, at least in NED! NED does list an HII region within a
couple seconds of arc of its position however. I can't see it against
the distant galaxy. In fact most of the fuzzy objects in my image don't
have any catalog entry that NED shows. Within 15' radius of Arp 68 NED
lists only 6 other galaxies, one one of which has a red shift listed.
You'll find this galaxy due east (left) of Arp 68 just above a rather
bright star. It is the X-ray galaxy GALEX 2690243303817875752 also at
120 million light-years. The very blue galaxy just below Arp 68 and a
tad to the east of its center is [HDL96] 407-017. I have nothing much
on it.

Most sources consider the companion just a coincidence of line of sight
that isn't related to Arp 68 in any way. It shows no sign of
interaction though NGC 7757 does seem somewhat disturbed. Arp noted the
arm saying "Many star-like knots lined up along straight arm." If it
has interacted with anything recently the only candidate appears to be
the other one at 120 million light years. Being an X-ray galaxy it has
apparently been fired up. But there's no real evidence the two ever
interacted. A better candidate might be be NGC 7750 about 39 minutes
southwest of Arp 68 so well out of my image. It also is about 120
million light years distant and is classed as (R')SB(rs)c pec:. They
are too far apart for one frame but I wish I'd realized it was there
last fall. I'll try for it this fall weather willing.

The image has quite a few asteroids in it. What's really annoying to me
is that THREE of them are unknown to the Minor Planet Center.
Unfortunately, I took this back last September and just recently found
the asteroids so there's no way to follow up. They are still lost
awaiting discovery it seems. I've "found" about 8 now that I've seen
months too late to follow up on. This is getting to be routine with me
it seems. I've included an annotated image that shows that identifies
the asteroids.

(91197) 1998 SD115 magnitude 18.3
2002 PY124 magnitude 19.2
2005 SZ152 magnitude 19.7
3 unknowns

This field is out of the Sloan survey area so there's very little data
available and no professional images, other than Arp's, that I could
find on the net.

Arp's image
http://nedwww.ipac.caltech.edu/level...big_arp68.jpeg
His image appears to have a plate defect at the southwest end of the
companion (right in his photo). It appears to be a round stain of some
sort.

Rick

Rick,

amazing detail in this smallish galaxy.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
. com...
Arp 68/NGC 7756 is a Sc spiral galaxy in Pisces at about 120 million
light-years. Arp included it in his category Sprial Galaxies with small
high surface brightness companions on arms. I'd have put it in his
heavy arm category as the "companion" appears to be in the distant
background. Arp said the companion was NGC 7756. Lord Rosse who
discovered NGC 7756 and NGC 7757 said this about NGC 7756 "Another neb
about 5' sp (NGC 7757)." By "sp" he means south preceeding which is
south west. The only object 5' south west of NGC 7757 is a 12.8
magnitude rather white star. His description is a a match for NGC 7757.
No one doubts this is a double sighting of NGC 7757. The problem is
some sources, like Arp, claim the companion is NGC 7756. This obviously
isn't the case. The Kanipe-Webb book gets it right as does NED and the
NGC Project. But what is the designation of the companion? It doesn't
seem to have one, at least in NED! NED does list an HII region within a
couple seconds of arc of its position however. I can't see it against
the distant galaxy. In fact most of the fuzzy objects in my image don't
have any catalog entry that NED shows. Within 15' radius of Arp 68 NED
lists only 6 other galaxies, one one of which has a red shift listed.
You'll find this galaxy due east (left) of Arp 68 just above a rather
bright star. It is the X-ray galaxy GALEX 2690243303817875752 also at
120 million light-years. The very blue galaxy just below Arp 68 and a
tad to the east of its center is [HDL96] 407-017. I have nothing much
on it.

Most sources consider the companion just a coincidence of line of sight
that isn't related to Arp 68 in any way. It shows no sign of
interaction though NGC 7757 does seem somewhat disturbed. Arp noted the
arm saying "Many star-like knots lined up along straight arm." If it
has interacted with anything recently the only candidate appears to be
the other one at 120 million light years. Being an X-ray galaxy it has
apparently been fired up. But there's no real evidence the two ever
interacted. A better candidate might be be NGC 7750 about 39 minutes
southwest of Arp 68 so well out of my image. It also is about 120
million light years distant and is classed as (R')SB(rs)c pec:. They
are too far apart for one frame but I wish I'd realized it was there
last fall. I'll try for it this fall weather willing.

The image has quite a few asteroids in it. What's really annoying to me
is that THREE of them are unknown to the Minor Planet Center.
Unfortunately, I took this back last September and just recently found
the asteroids so there's no way to follow up. They are still lost
awaiting discovery it seems. I've "found" about 8 now that I've seen
months too late to follow up on. This is getting to be routine with me
it seems. I've included an annotated image that shows that identifies
the asteroids.

(91197) 1998 SD115 magnitude 18.3
2002 PY124 magnitude 19.2
2005 SZ152 magnitude 19.7
3 unknowns

This field is out of the Sloan survey area so there's very little data
available and no professional images, other than Arp's, that I could
find on the net.

Arp's image
http://nedwww.ipac.caltech.edu/level...big_arp68.jpeg
His image appears to have a plate defect at the southwest end of the
companion (right in his photo). It appears to be a round stain of some
sort.

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".