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ASTRO: Arp 331 -- The Pisces Cloud



 
 
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  #1  
Old August 26th 09, 09:05 PM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Posts: 3,085
Default ASTRO: Arp 331 -- The Pisces Cloud

Arp 331 is another galaxy chain. Again they are ellipticals. The
galaxies are all part of a larger group which is part of a still larger
group. Arp 331 apparently refers only to the chain. The entire cluster
of galaxies, larger than my image is often called the Pisces Cloud or
more formally Zwicky 0107.5+3212. It is made of several parts of which
C2 contains this chain and many of the other galaxies in my image.
Though to add to the confusion some sources consider the Pisces Cloud to
only be the chain, others expand it to up to 12 galaxies. See the
annotated image to identify the galaxies in the chain region. Many are
NGC galaxies. Only one galaxy major galaxy didn't fit on the cropped
and reduced ID image. It is PGC 4021 which is about 2/3rds of the way
from NGC 383 and the upper left corner. It too is likely a member of
the group. Note some catalogs call it NGC 390. That is not correct, at
least per the original NGC data. NGC 390 is a star in the field of the
ID image so I noted it. It was found by Bigourdan who had a reputation
for seeing stars as galaxies. His description says very faint --
stellar. Same as he usually said about his galaxies that turned out to
be stars. He missed nearby PGC 4021. Visual observations are no where
near as reliable as today's photographic ones but they aren't perfect
either as we'll see in an Arp galaxy I'm currently researching.

The Pisces Cloud is thought to be a bit over 200 million light years
away. All of the galaxies show a redshift distance of between 180 and
240 million light years. The range is reasonable for orbital motions
expected in such a cluster. Arp's comment on the chain was "Symmetry
around large central galaxy." Arp's image of the chain is oddly
underexposed. It is at:
http://nedwww.ipac.caltech.edu/level...ig_arp331.jpeg
Because of the exposure the distance between galaxies seems larger than
in my image. Judging by the length of an asteroid trail in his image
I'm going to guess his exposure was about 15 minutes long with an
uncertainty of +/- 5 minutes. Their speed can vary greatly depending
where they are in the asteroid best and where they are in the sky when
imaged.

The image is full of orange "stars" that are really galaxies. For
instance half way between the spiral UGC 679 and PGC 1995971 are two of
these star-like galaxies. One is slightly above and right of the other,
it is very orange. A bit closer and below is a yellow white "star" that
is also a spherical galaxy. I have no red shift or other distance
indicator but suspect they are part of the same group, just smaller
members. They appear like a double star each of which is slightly
elongated.

I had to move the field further north than I wanted due to the 6th
magnitude star. When I centered everything it was out of the field but
sending in some nasty ghosts. The only way to get rid of the worst of
them was to move it into the FOV. For some reason my filters scatter
more green and blue than red light so even though it is a K0 star it has
a rather cyan halo from the excess green and blue. I didn't try to fix
this.

Many galaxies in the image I didn't mention had red shift data. All of
which indicate they are members of this group. Far more either had no
red shift data or weren't in any catalog. This area hasn't been covered
by SDSS. The only galaxy without red shift data I've pointed out on the
annotated image is PGC 1992085. I see no reason it couldn't be a member
but that's unknown for sure.

This one was imaged Nov. 18, 2008 UT.

14" LX200R @ f/10, L=5x10' RGB=2x10', STL-11000XM, Paramount ME

Rick


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  #2  
Old August 27th 09, 03:58 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Posts: 3,085
Default ASTRO: Arp 331 -- The Pisces Cloud

I forgot to include the ID image.

Rick

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  #3  
Old September 2nd 09, 10:27 PM posted to alt.binaries.pictures.astro
Stefan Lilge
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Posts: 2,269
Default ASTRO: Arp 331 -- The Pisces Cloud

Nice picture Rick. I haven't heard of this chain of galaxies before.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
. com...
Arp 331 is another galaxy chain. Again they are ellipticals. The
galaxies are all part of a larger group which is part of a still larger
group. Arp 331 apparently refers only to the chain. The entire cluster
of galaxies, larger than my image is often called the Pisces Cloud or
more formally Zwicky 0107.5+3212. It is made of several parts of which
C2 contains this chain and many of the other galaxies in my image.
Though to add to the confusion some sources consider the Pisces Cloud to
only be the chain, others expand it to up to 12 galaxies. See the
annotated image to identify the galaxies in the chain region. Many are
NGC galaxies. Only one galaxy major galaxy didn't fit on the cropped
and reduced ID image. It is PGC 4021 which is about 2/3rds of the way
from NGC 383 and the upper left corner. It too is likely a member of
the group. Note some catalogs call it NGC 390. That is not correct, at
least per the original NGC data. NGC 390 is a star in the field of the
ID image so I noted it. It was found by Bigourdan who had a reputation
for seeing stars as galaxies. His description says very faint --
stellar. Same as he usually said about his galaxies that turned out to
be stars. He missed nearby PGC 4021. Visual observations are no where
near as reliable as today's photographic ones but they aren't perfect
either as we'll see in an Arp galaxy I'm currently researching.

The Pisces Cloud is thought to be a bit over 200 million light years
away. All of the galaxies show a redshift distance of between 180 and
240 million light years. The range is reasonable for orbital motions
expected in such a cluster. Arp's comment on the chain was "Symmetry
around large central galaxy." Arp's image of the chain is oddly
underexposed. It is at:
http://nedwww.ipac.caltech.edu/level...ig_arp331.jpeg
Because of the exposure the distance between galaxies seems larger than
in my image. Judging by the length of an asteroid trail in his image
I'm going to guess his exposure was about 15 minutes long with an
uncertainty of +/- 5 minutes. Their speed can vary greatly depending
where they are in the asteroid best and where they are in the sky when
imaged.

The image is full of orange "stars" that are really galaxies. For
instance half way between the spiral UGC 679 and PGC 1995971 are two of
these star-like galaxies. One is slightly above and right of the other,
it is very orange. A bit closer and below is a yellow white "star" that
is also a spherical galaxy. I have no red shift or other distance
indicator but suspect they are part of the same group, just smaller
members. They appear like a double star each of which is slightly
elongated.

I had to move the field further north than I wanted due to the 6th
magnitude star. When I centered everything it was out of the field but
sending in some nasty ghosts. The only way to get rid of the worst of
them was to move it into the FOV. For some reason my filters scatter
more green and blue than red light so even though it is a K0 star it has
a rather cyan halo from the excess green and blue. I didn't try to fix
this.

Many galaxies in the image I didn't mention had red shift data. All of
which indicate they are members of this group. Far more either had no
red shift data or weren't in any catalog. This area hasn't been covered
by SDSS. The only galaxy without red shift data I've pointed out on the
annotated image is PGC 1992085. I see no reason it couldn't be a member
but that's unknown for sure.

This one was imaged Nov. 18, 2008 UT.

14" LX200R @ f/10, L=5x10' RGB=2x10', STL-11000XM, Paramount ME

Rick




 




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