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Thread: Arp 199 under very poor seeing conditions

  1. #1
    Join Date
    Dec 2006

    Arp 199 under very poor seeing conditions

    NGC 5544 looks like a barred spiral with an inner ring connected to the bar and a nearly equally bright outer ring not connected to the bar. Other than the double ring it doesn't appear all that disturbed to me though parts of it are hidden behind the obviously closer NGC 5545. NED classes it as (R)SB(rs)0/a. The NGC Project disagrees saying it is an ordinary Sa spiral with no bar. Sure looks like a bar to me.

    NGC 5545 appears to be a somewhat disturbed spiral. NED classes it SA(s)bc while the NGC Project say Sb-c using its simpler system. At least they agree on this one. Red shift puts NGC 5545 slightly further away which can't be correct since it is hiding part of NGC 5544 which is slightly closer by redshift alone. The difference is due to both measuring accuracy and relative velocity. Thus NGC 5544 is moving toward NGC 5545 so the collision, if there is one, is still in the future. What we can't measure is the lateral velocity. It could be that NGC 5545 will have moved to the side by the time NGC 5544 gets to its distance.

    The other NGC galaxy is NGC 5557 in the lower left of my image. It's distance by redshift is slightly greater than Arp 199. Still it is quite likely they are part of the same group of galaxies. The NGC project classes it simply as E. It certainly is an elliptical. NED calls it E1 and a note at NED says it is classic E2. These classifications would indicate it is slightly elongated which it appears to be in my image.

    In making the annotated image I accidentally ran across three galaxies not in NED's database even though many far fainter and smaller galaxies were included. Two of the three are very blue which seems to often be the case. Some systematic error must be at play here. The three are marked by a question mark. I didn't search for others so likely there are more in the image.

    Also look left (east) and slightly north (up) of Arp 199. There's an area of a faint glow. I thought this a reflection at first but went back through my data to find an unusable frame from a year previously taken with a quite different camera position, better framing NGC 5557 with Arp 199. The glow is seen in this image at exactly the same spot so must be real. Probably some faint IFN or something akin to it.

    Seeing was very poor when this was taken. I'd hoped to retry it by now but this year has been far worse for both seeing and transparency than last so it isn't happening (snowing very lightly as I type this). This fuzzy version will have to do for now.

    Sloan image:

    Arp's image:

    14" LX200R @ f/10, L=4x10 RGB=2x10x3, STL-11000XM, Paramount ME

    Attached Images Attached Images

  2. #2
    Join Date
    Sep 2005
    Very Beautiful and interesting info on there distances and other galaxies in this fov. I hope your weather improves for you and thanks for sharing this great info Rick.

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