Arp 198 - Interacting galaxies? Spiral ejecting material from its nucleus? Or…
Leo
RA 10 59 78
DEC +17 39 03
Magnitude 15.2 and 15.3
Size: 1.3 x 0.8 and 0.9 x 0.15
I was able to observe Arp 198 early this past March on a delightfully dark and transparent night with my 28-inch scope. At the time it was just another Arp I hadn’t observed before, but after enjoying it so much I did a little research and, as is often the case, found that it’s even more interesting than I first thought.
At first glance Arp 198 looks like a fairly classic pair of interacting galaxies – a face-on spiral and an edge-on galaxy in the beginning stage of a merger. On the other hand, Halton Arp thought this was a case of the face-on spiral ejecting material from its nucleus. That would be super cool if true, but it turns out neither of these scenarios are correct.
The true state of affairs seems to be that the face-on spiral is in the foreground and the edge-on is in the background – the two galaxies are merely a chance superimposition. The face-on is cataloged as VV267a and is about 506 million light years away, while the edge-on, VV267b, is about 673 million light years distant. The SDSS image bears this out with VV267a having an overall blue color while VV267b is obviously yellow.
Arp 198_SDSS_DR12.JPG
My observing notes: “…Arp 198 is subtle and only gradually shows two brightenings, seemingly projecting directly from the foreground MW star – a cool sight! Best at 408x, 547x was way too much power. 21.47 SQM.”
Arp198_sketch_crop2.jpg Arp198_sketch_cropinvert2.jpg
I expect Arp 198 could be well-seen in a 16-inch scope on a good night, and if you haven’t already observed this pair, well, you know what to do!
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