|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
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 |
#2
|
|||
|
|||
ASTRO: Arp 331 -- The Pisces Cloud
I forgot to include the ID image.
Rick |
#3
|
|||
|
|||
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 |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
ASTRO: Hind's Variable Nebula, a huge molecular cloud and 9 asteroids-- no waiting | Rick Johnson[_3_] | Astro Pictures | 2 | February 19th 08 12:28 AM |
ASTRO:NOCTILUCENT CLOUD | Azz | Astro Pictures | 10 | July 3rd 07 08:21 PM |
ASTRO: M-74, spiral galaxy in Pisces | George Normandin | Astro Pictures | 8 | December 25th 06 04:20 PM |
ASTRO: wide-field centered on Scutum star cloud | George Normandin[_1_] | Astro Pictures | 3 | November 19th 06 06:10 AM |
pisces?? | Thomas McDonald | Astronomy Misc | 1 | August 9th 03 08:54 AM |