Galaxy Zoo Talk

1.3+ million light year tidal tail from galaxy pair Mrk 926?

  • planetaryscience by planetaryscience

    While searching for a long-lost asteroid on a very unusual orbit, I happened across this pair of equally unusual galaxies. The brighter is Mrk 0926, and is pretty obvious for its AGN.

    (Would embed an image here but I still have no idea how to resize images, just see: https://i.imgur.com/1K6bEt9.jpg?1)

    The secondary galaxy seemed to have a bit of a tail to the south, so I scrolled further down and found this impressive thing:

    https://i.imgur.com/xX5SO37.jpg?1

    Zoomed out: https://i.imgur.com/HG7F0Qt.jpg?1

    I calculated that if this is indeed related to the galaxy, it would be over 1.3 million light years across at the very least, and possibly more if it's not completely edge-on. Is that unusually large for tidal tails? I haven't looked much into it, but ever famous ones like the tadpole galaxy are less than 300,000 light years across, leading me to believe this is quite long even among tails.

    Posted

  • Ghost_Sheep_SWR by Ghost_Sheep_SWR

    Perhaps next time add coordinates, saves a pre-search search. RA,Dec 346.2012 -8.7568

    Does seem to be a straight line from the secondary galaxy, which would be strange in itself (a straight line from interaction?), although it's very faint.

    Difficult to tell for sure,perhaps a tad better visible in DECaLS SDSS:

    enter image description here

    http://legacysurvey.org/viewer?ra=346.2008&dec=-8.7548&zoom=12&layer=sdss2


    Hmm if it is related to 2MASX J23044397-0842114

    it is at redshift z=0.04702, and I measure a distance of the perceived tail of ~ 6,4' from galaxy to the 'clumps' in between the two bright stars at bottom.

    Size of an object of 1 arcsec at z=0.047 is roughly 0.96 kpc: 6,4 arcminute is 384 arcsec * 0.96kpc = ~ 368.64 kpc which is about 1.2 million lightyears, so yeah I get the same order of magnitude for size.

    Would be very cool, although seems strange to me it would be perfectly straight, but if it is related / tidal tail perhaps it makes a large U-shape in our line-of-sight.

    Source for estimating size at given redshift z: https://arxiv.org/abs/1303.5961

    Posted

  • mlpeck by mlpeck

    Long straight tails of apparently tidal origin aren't unknown. One spectacular example is the "Superantennae" (Mirabel, Lutz & Maza 1991).

    Zwicky studied these quite extensively decades ago and claimed to have found many thousands of examples of extended tidal features in plates (!) from the Palomar Schmidt cameras (Zwicky 1956, for example).

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  • planetaryscience by planetaryscience in response to mlpeck's comment.

    Interesting! I wasn't able to find many examples of particularly tidal tails- but apparently that confirms that if confirmed, this thing would be the longest known tidal tail (unless any research between 1991 and 2017 has anything to say about that... which I'm sure it does)

    Posted

  • planetaryscience by planetaryscience in response to Ghost_Sheep_SWR's comment.

    Thanks for the analysis- the images I posted were from DECaLS, but ironically it seems a higher resolution is worse at seeing the clumps. Here's a heavily layered image I made: https://media.discordapp.net/attachments/280053526514630657/387546497610416139/image.png

    It seems like the above might be the clearest image it's possible to get of the clumps. The estimation of 1.3 million light years was including the primary galaxy, as well as the faintest bits of the clumps: Together, it's about 7.1 x 2.4, or about 430 kpc/1.4 mly- 1.3 mly just to be conservative. It could, as you say, be curved though. Now that'd be interesting- maybe even measurable? If it's at a 45 degree angle to us, the closest point would be ~z=0.00005 closer to us.

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  • Ghost_Sheep_SWR by Ghost_Sheep_SWR in response to mlpeck's comment.

    Thanks for the links and background info, very informative.

    Was thinking perhaps a real straight line tidal tail might be possible from a head-on collision in the distant past (without any significant relative peculiar motion and huge starting difference velocity)?

    Posted

  • planetaryscience by planetaryscience in response to Ghost_Sheep_SWR's comment.

    Well the pair is definitely set up to have significant tidal interaction at this point- if you look closely at the last image I sent, you can see that Markarian 926 has quite a few tidal shells around it- not to mention that it's a seyfert galaxy. I'd bet they've gone right through each other a few times already.

    Posted