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View Full Version : Minkowski's Object and lots more



RickJ
2011-Nov-30, 08:52 AM
Another Arp pair. These are located in the Abell 194 galaxy cluster. The cluster is located in north central Cetus about 230 million light-years away.

Arp 133 falls under Arp's very odd category of galaxies with nearby fragments. It consists of two galaxies, NGC 541 the large cD/S0 galaxy to the southwest of a pair of elliptical galaxies that are Arp 308. The fragment is the very blue dwarf galaxy to its northeast (upper right). This is not a fragment at all but a dwarf galaxy undergoing extreme starburst star formation. It is known as Minkowski's Object. NGC 541 is a radio galaxy with jets. One is directed directly at Minkowski's Object and is credited with triggering the starburst activity. Minkowski's Object has a different redshift but this is more an indication of relative velocity than a real distance difference. Arp 133 with its blue companion galaxy is almost identical in appearance to the much nearer Arp 134 (M49 and its blue "fragment" UGC 07636.) http://www.spacebanter.com/attachment.php?attachmentid=2440&stc=1

Arp had no knowledge of this at the time of his image. His image carries a note that it was taken with a "Poloroid" filter. I assume he means polarizing filter. How it was aligned it doesn't say. Arp's comment on the image reads: "Central member of galaxy group associated with 3C40." 3C40 is a strong radio source. This is not the radio source involved with the starburst activity in Minkowski's Object. But it does bring us to Arp 308.

Arp 308 is a pair of galaxies; NGC 545 and NGC 547 that is associated with the radio source 3C40. That is NGC 547 is considered to be the source of 3C40. Arp put the pair in his category of simply double galaxies. His simple remark says: "Close ellipticals." which isn't very informative. NGC 545 to the north is listed as an SA0 galaxy while NGC 547 is E1 and a bright cluster galaxy. Redshift puts it at 6 million light-years further from us that NGC 545. However NED gives a D-Sigma distance determination that is the same for both. Likely the difference in radial velocity is due to relative motion rather than distance. The exact same D-Sigma distance is found for NGC 541 (Arp 133) as well. A 1964 paper concludes NGC 545 is not interacting with NGC 547. I find that hard to accept.

Notes about the annotated image.
Objects considered part of Abell 194 are listed by name.

Redshift distance using NED's 5 year WMAP assumptions are used. They are expressed in billions of light-years. Differences in cluster member radial velocity is most likely due to relative velocity around the clusters center of mass rather than a true distance indicator. Most, likely lie within a few million light-years of each other. The label is immediately right of the object when possible. Otherwise a line will connect the object and its label.

XMMU J012535.9-012546 is an X-ray galaxy. It appears to be a very compact dwarf of some sort.

ARK 45: A note at NED says "Together with NGC 0547 this is the radio source 3C 40." I'm not sure how this was determined, especially since NGC 545 is in the middle yet not considered part of 3C 40 that I found. Also note its redshift is surprisingly different.
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NSCS J012537-011739 is a galaxy cluster at 4.97 billion light-years. It contains 36 members. The diameter isn't specified. I see a dozen or two within a few minutes of the center. Many look like faint stars.

WHL J012538.1-011301 is another galaxy cluster at 5.3 billion light-years. It contains only 8 members. It's center is a couple seconds of arc from a faint galaxy, probably the anchoring member. The NED position is only approximate so likely means to point to this galaxy.

The UvES (Ultraviolet Excess Source) is likely a quasar given its distance.

Arp's image of these galaxies is made from the same plate and cropped to exclude the other atlas entry. Most of his images are are shorter than the one hour exposure on 103a-0 image. The added time is likely due to losses in the "Poloroid" filter. He lists the seeing as average 1" to 1.5".

Arp's image of Arp 133 with an asteroid trail:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp133.jpeg

Arp's image of Arp 308
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp308.jpeg

14" LX200R @ f/10, L=4x10' RGB=2x10'x3, STL-11000XM, Paramount ME

Rick