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Thread: Arp 189 Even more plumes (explained this time)

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    Join Date
    Dec 2006

    Arp 189 Even more plumes (explained this time)

    Arp 189/NGC 4651, the Umbrella Galaxy, is a member of the Virgo Cluster of galaxies in the constellation of Coma Berenices. As such it is about 60 million light-years distant. So I'm a bit perplexed with its coverage by NASA's Astronomical Picture of the Day entry for it. They say it is 35 million light-years distant which removes it from the cluster. It's redshift distance is about 51 million light-years while NED lists many distance measurements by Tully-Fisher averaging about 85 million light-years and a Sosies measurement of 77 million light-years. Nothing agrees to APOD's 35 million light-year distance. In other words does anyone really know its distance?

    Arp put it in his category of galaxies with narrow filaments. His comment reads: "Radio source near tail apparently not associated." We now know that its odd structure is due to it eating another galaxy in the recent past. The "narrow filament" is the remains of the galaxy showing its path around the galaxy as it was torn apart by gravitational tidal forces.

    Unfortunately my data on this one is poor. The camera's hex screws worked loose in the vast temperature swings of last winter allowing the camera to tilt. I eventually caught and corrected it but missed that this one needed a reshoot. Color data was hurt even more the the luminosity data due to the changing angle of the telescope. Red was completely out of focus. This has resulted in poor color balance and nasty red rings around many stars, even blue ones. It is on the retake list for this and to get more data to pick up the "umbrella" better than my meager 40 minutes did. Now if the snow and clouds will ever quit!

    I prepared an annotated image as there were some very distant galaxies on the east side of Arp 189. Probably on the other sides as well but for some reason the Sloan survey only took redshift data on a very small area of my image. All of it on very distant galaxies and one quasar. The quasar is closer than many of the galaxies! While my image is poor in focus it did go deep anyway with galaxies down to 23rd magnitude recorded. You may need to blow up the image to find some of these very faint ones. When you do you will find the field jammed with tiny faint fuzzy spots. I had thought this just background noise but when I looked up the position of these 22nd magnitude and fainter galaxies at 5 and even 6 billion light-years there was one of these fuzzy blobs dead on the position. Most agreed to a few hundredths of a second of arc. If off by more than the error circle of the SDSS data I skipped it. Only happened once. In one 10" circle that I tested there were 5 and every one had an entry in the catalog though only 1 had redshift data. Thus, I'm quite sure these faint blobs (blow up the image 3x or more to see them) are distant galaxies.

    There are three asteroids in my image, all within the faint tidal plumes. They are shown on the annotated image. The bright one (left) is magnitude 18.3 while the other two are 20.0 (center) and 19.9 (right) per estimates of the minor planet center.

    Arp's image:

    APOD image much deeper than any of the above or mine with overlay of the path of the doomed satellite galaxy:

    14" LX200R @ f/10, L=5x10' RGB=2x10'x3, STL-11000XM, Paramount ME

    Attached Images Attached Images

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