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Mike JW

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Although it is more than 30 years old now, the 1990 paper New observations and a photographic atlas of polar-ring galaxies by Whitmore et al [1] makes for fascinating reading and inspection, containing as it does a catalogue and images of over 150 such polar ring galaxies (PRG), candidate PRGs, and other similar-looking and possibly related objects. 

The catalogue lists 6 confirmed PRGs (category A), 27 probable PRGs (cat. B), 73 possible PRGs (cat. C) and 51 objects that might be related to PRGs, or are unrelated but could be mistaken for PRGs (cat. D). This latter category includes 'box, peanut and X-galaxies' (the latter like NGC 128 above in this thread), smoke-ring galaxies, Hoag-type and Mayall-type galaxies, and superpositions that just happen to look like PRGs, amongst others. The paper is well worth a browse, though following objects up with more recent observations is necessary as I imagine some of the objects will have changed category by now.

I observed 5 members of this catalogue last night, 3 from cat. C and 2 from cat. D. and include 4 of them below (one was lost in the murk).


PRC C-71 in Pisces. This is labelled PRC 141 in my image (as I made a quick catalogue from the paper and haven't yet sorted out all the proper names). This is a possible PRG showing the x-structure, but could also be a chance superposition like D-49 below. It really is not clear either from the DSS image on Aladin which interpretation is correct.



Contrast the above with PRC D-49 in Aquarius. This is regarded as a 'superposition that resembles a PRG'. The superposition of the two galaxies is really clear here. The galaxy 'pair' is listed at b mag 18.6 but looks much brighter to me. Some of the outer parts of the larger spiral can be made out. One wonders what the actual relative distances of these two members are and what the chances are of a near-perfect line of sight superposition with the galaxy centres lining up like this. D-49 is a member of Abell 2258. I found this chance alignment one of the more fascinating observations I've made using EEVA.



PRC D-32 in Capricorn (not shown) at -23 degrees dec was too low for me to make out any details. I might revisit this on another day, although the DSS image is not much to write home about.

PRC C-66, also in Capricorn at a healthier -16 degrees dec, was one of the surprises of the night. Individual subs showed no hint of anything exciting, but as the stack built up a clear long tail to the south appeared followed by hints of a multiplicity of short counter-tails to the NNW and a possible double-core in the galaxy itself. The SDSS image on Aladin also indicates 2 core-like nuclei and shows the upper tail to undergo a sharp 90 turn to the left (WSW) which then of course becomes obvious in my image... This is a member of Abell 2150.





The most confusing field of the night is the one containing PRC C-58 (labelled PRC 90 here), also in Capricorn. This was captured through bushes at an altitude of under 20 degrees (decl. -25) so the shot is pretty grainy. The description in the catalogue is a little contradictory because PRC C-58 is identified with NGC 7016, but the text suggests the candidate is actually the double-core object near the centre of the shot (NGC 7017). There is an almost mirror-image double galaxy/galaxy pair to the north of the shot too (one member is NGC 7018). NGC 7017 + 7016 is classified as VV 1906, while NGC 7018 is VV 764. These are all members of Abell 3744. It turns out that NGC 7016 and 7018 are radio galaxies near the centre of the cluster. Article [2] describes them in great detail (= I've only skimmed it!). There are some fascinating structures visible at those wavelengths. In the visible wavelength image of this field in the 1990 article there is a hint of a jet to the lower right of NGC 7016 (terrestrial SE, astronomical SW) -- confirmed, I believe, in [2] -- that looks like it would be a challenging object to capture using EEVA techniques if anyone lives at a sufficiently southerly latitude!



I'll certainly be revisiting this catalogue as the season progresses and will be happy to make the catalogue available when I've tidied up the names.


[1] http://simbad.u-strasbg.fr/simbad/sim-ref?bibcode=1990AJ....100.1489W
[2] https://research-information.bris.ac.uk/ws/portalfiles/portal/39386034/1312.5311v1

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  • 4 weeks later...

NGC 561 in Andromeda.  As you can see from the caption details I was not going for 561. I was in fact taking a look at FGC 170 but when the image appeared on the screen, there was this ring galaxy and all sorts of other objects of interest - faint galaxies, quasars and a 3 pairs of stairs surrounding the faint PGC 




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