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ASTRO: ZwCl 2247.3+1107 Galaxy Cluster
NGC 7385 is the largest and brightest member of the ZwCl 2247.3+1107
galaxy cluster. This cluster has 162 members over a field 2.3 degrees across that is centered about 5 minutes below the bottom of my image. Yet the major NGC galaxies are located north of the center so that's where I pointed the scope. Zwicky put the cluster in his "Open" category. This means it has no defined center and galaxies are rather evenly scattered showing no grouping toward the center. I've listed the classification, if any was given along with the redshift distance in billions of light-years in the annotated image. As well as the one asteroid in the image. But some galaxies are interesting so I'll cover what I found interesting about them. NGC 7385 is not only the biggest and brightest galaxy in the group it is the most disturbed as well. There is an obvious stream of something going southwest from the galaxy toward PGC 069819 then angling northwest to a point just northeast of NGC 7383 where it turns nearly straight north. It is faint but you should see it. Maxing out the contrast of the Red POSS 2 plate shows it clearly as well. I was thinking it likely IFN which is seen in parts of Pegasus but then found a note to NGC 7385 at NED that said: "Huge radio source extending southwest..." That appears to match this feature indicating it really is a plume. This brings me to NGC 7383. A note at NED says it is a non interacting companion to NGC 7385. What caused the plume. Could NGC 7385 be involved after all. It's eastern arm on the side toward NGC 7385 and the plum is longer and more disturbed look than the one on the western side. Could there be a connection to all this? I'm not ready to be certain there's no interaction, just that it may be unlikely. NGC 7386 to the north of NGC 7385 is the second largest galaxy in the cluster. A note at NED says it is a non interacting companion to NGC 7385. But again, I'm not quite ready to say that's the case. There is a faint stream of material between the two. Fainter than the southwest plume but again visible on the POSS II plate. While the redshift of NGC 7383 and NGC 7385 are virtually the same that of NGC 7386 is a bit different. The plumes of NGC 7385 may be due to some galaxy it digested in the past and have nothing to do with these other two galaxies which just happen to be in the path of what it was that NGC 7385 ate. The sudden turn of the plume could be from the galaxy passing by, slowing down and being pulled back to make its final plunge into NGC 7385. I consider this more likely than the other two NGC galaxies being involved but I'd like to see deeper photos of the plume. That might decide the issue. Another galaxy pair is MCG+02-58-023. The northern member of the pair is NGC 7387. NED has a redshift for NGC 7383 of 7118 for a time travel of 310 million years. NED also lists a redshift for the pair under the MCG+02-58-023 designation of 7756 for a light travel time of 340 million years. I can't explain the discrepancy so have put both measurements on the image under the NGC 7387 label. One more thing about NGC 7385. Several cD galaxies in major clusters I've imaged (M49 is an example) have blue galaxies that appear like a bug splat on the "front" of the galaxy. NGC 7385 has one as well on the northeast side. In the case of the others I've imaged the blue galaxy was a dwarf member of the cluster and well studied. That isn't the case here. It isn't listed in NED at all! So I have no idea if it too is a dwarf member of the group or a distant background galaxy. I prefer the former but without any data can't back that up in any way other than blue galaxies like it are rarely seen by my scope at distances much greater than that of this cluster. Also the blue color may indicate interaction with NGC 7385. It is remotely possible it is destined for its next meal or not. There's no way to know with what little information is currently available. While there are a lot of faint and not so faint galaxies in the image not found at NED I've listed all with redshift data. Another 10 or so are listed without redshift data with the vast majority not listed at all. This is an area of the sky close enough to the exclusion zone that even though it is well populated most surveys have ignored the area. A few more are listed in The Sky under extended PGC labels that NED is yet to pick up. I didn't list them since you can't go to NED or SIMBAD and look them up nor does the The Sky database have redshift data. This would be a good area for those with a larger field of view than mine to look into that are interested in galaxy clusters. 14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME Rick -- Prefix is correct. Domain is arvig dot net |
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ASTRO: ZwCl 2247.3+1107 Galaxy Cluster
Beautiful image Rick.
There is detail in quite a lot of these small galaxies. Stefan "Rick Johnson" schrieb im Newsbeitrag ... NGC 7385 is the largest and brightest member of the ZwCl 2247.3+1107 galaxy cluster. This cluster has 162 members over a field 2.3 degrees across that is centered about 5 minutes below the bottom of my image. Yet the major NGC galaxies are located north of the center so that's where I pointed the scope. Zwicky put the cluster in his "Open" category. This means it has no defined center and galaxies are rather evenly scattered showing no grouping toward the center. I've listed the classification, if any was given along with the redshift distance in billions of light-years in the annotated image. As well as the one asteroid in the image. But some galaxies are interesting so I'll cover what I found interesting about them. NGC 7385 is not only the biggest and brightest galaxy in the group it is the most disturbed as well. There is an obvious stream of something going southwest from the galaxy toward PGC 069819 then angling northwest to a point just northeast of NGC 7383 where it turns nearly straight north. It is faint but you should see it. Maxing out the contrast of the Red POSS 2 plate shows it clearly as well. I was thinking it likely IFN which is seen in parts of Pegasus but then found a note to NGC 7385 at NED that said: "Huge radio source extending southwest..." That appears to match this feature indicating it really is a plume. This brings me to NGC 7383. A note at NED says it is a non interacting companion to NGC 7385. What caused the plume. Could NGC 7385 be involved after all. It's eastern arm on the side toward NGC 7385 and the plum is longer and more disturbed look than the one on the western side. Could there be a connection to all this? I'm not ready to be certain there's no interaction, just that it may be unlikely. NGC 7386 to the north of NGC 7385 is the second largest galaxy in the cluster. A note at NED says it is a non interacting companion to NGC 7385. But again, I'm not quite ready to say that's the case. There is a faint stream of material between the two. Fainter than the southwest plume but again visible on the POSS II plate. While the redshift of NGC 7383 and NGC 7385 are virtually the same that of NGC 7386 is a bit different. The plumes of NGC 7385 may be due to some galaxy it digested in the past and have nothing to do with these other two galaxies which just happen to be in the path of what it was that NGC 7385 ate. The sudden turn of the plume could be from the galaxy passing by, slowing down and being pulled back to make its final plunge into NGC 7385. I consider this more likely than the other two NGC galaxies being involved but I'd like to see deeper photos of the plume. That might decide the issue. Another galaxy pair is MCG+02-58-023. The northern member of the pair is NGC 7387. NED has a redshift for NGC 7383 of 7118 for a time travel of 310 million years. NED also lists a redshift for the pair under the MCG+02-58-023 designation of 7756 for a light travel time of 340 million years. I can't explain the discrepancy so have put both measurements on the image under the NGC 7387 label. One more thing about NGC 7385. Several cD galaxies in major clusters I've imaged (M49 is an example) have blue galaxies that appear like a bug splat on the "front" of the galaxy. NGC 7385 has one as well on the northeast side. In the case of the others I've imaged the blue galaxy was a dwarf member of the cluster and well studied. That isn't the case here. It isn't listed in NED at all! So I have no idea if it too is a dwarf member of the group or a distant background galaxy. I prefer the former but without any data can't back that up in any way other than blue galaxies like it are rarely seen by my scope at distances much greater than that of this cluster. Also the blue color may indicate interaction with NGC 7385. It is remotely possible it is destined for its next meal or not. There's no way to know with what little information is currently available. While there are a lot of faint and not so faint galaxies in the image not found at NED I've listed all with redshift data. Another 10 or so are listed without redshift data with the vast majority not listed at all. This is an area of the sky close enough to the exclusion zone that even though it is well populated most surveys have ignored the area. A few more are listed in The Sky under extended PGC labels that NED is yet to pick up. I didn't list them since you can't go to NED or SIMBAD and look them up nor does the The Sky database have redshift data. This would be a good area for those with a larger field of view than mine to look into that are interested in galaxy clusters. 14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME Rick -- Prefix is correct. Domain is arvig dot net |
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