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Thread: Arp 61 another galaxy pair

  1. #1
    Join Date
    Dec 2006

    Arp 61 another galaxy pair

    After the dud of Arp 150 I'm cleaning out my duds with another. This time it is Arp 61. Like Arp 150, I was trying to shoot binned 1x1 but again got clobbered. This time clouds hit the color data hard. I ended up cropping the image as things get really bad further away from the center. I was going to reshoot it but every time I tried something went wrong. I wanted at least double the luminosity data as well as 4 times the color data but seeing never cooperated. This one will go back on the list for next year. Though it seems jinxed. Even Arp did poorly with it as his photo of it is also rather poor showing no more detail than I do. Enough excuses here's the info on it.

    Arp 61 is a pair of galaxies. But probably not the pair you first think of seeing my cropped image. The galaxy to the lower right, MGC +00-12-053 is not part of Arp 61. Arp 61 is a pair of galaxies carrying the designation UGC 3104. It consists of the main galaxy, a spiral classed as Sa by NED. The other one is at the upper right (NW) end of the galaxy in my image. It appears to be a lenticular galaxy. NED shows its dimensions as 9 seconds of arc by 7 seconds of arc. Arp classed the pair as: Spirals with companions on arms; Small high surface brightness companions. I could find no information on the companion and the one note at NED says "companion?" meaning the writers didn't know if it was truly associated or just a line of sight pair that were not at all related. I see no hint of distortion to either so suspect that if they are related they certainly aren't interacting. NED puts the distance to the main galaxy, based on redshift, at a bit under 440 million light years.

    NED has little data on the third galaxy MGC +00-12-053. Without redshift data I can't tell if it is in the group with Arp 61 or not. There is a large S0 galaxy, UGC 3105, out of the cropped frame to the east that is about 400 million light years distant per red shift, close enough it may be related to Arp 61. Out of both frames to the west is MCG +00-12-050 and MCG +00-12-048 with red shifts that put them 450 and 422 million light years distant. All would be in my normal 1" per pixel image. They too could be part of the a group that includes Arp 61. Though I found nothing on this in the literature I looked at.

    Arp's photo with the 200" Palomar scope is at:

    I'm attaching two versions, one a 0.5" per pixel crop of just Arp 61 and another of the full frame at 1" per pixel to hide some of the noise. I only took half of my normal frame so the "full" frame is still small.

    14" LX 200R @ f/10, L=4x10 RGB=2x10 all binned 1x1, STL-11000XM, Paramount ME

    Attached Images Attached Images

  2. #2
    Join Date
    Dec 2006
    Hi Rick:
    Or triplet, another excellent photo.
    Many greetings

  3. #3
    Join Date
    Sep 2005
    Very interesting group, You caught as much data as the 200in. Thanks for the info.
    Clear Skies

  4. #4
    Join Date
    Mar 2004
    Nice catch! I collect overlapping-galaxy pairs (too far apart to be interacting) for dust studies, and I had managed to miss that one from the Arp atlas. Cut, paste, whistle nonchalantly... and thanks for calling it out.

  5. #5
    Join Date
    Dec 2006
    I'll be interested if any dust is seen from the companion. If it is Sa as NED says some should be seen but not as likely if it is S0 or especially E3.

    When I was imaging this I figured the pair was the two main galaxies. I saw the Arp companion as a third star. I should read what Arp had to say before I take the image rather than afterwards.


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