Shakhbazian 223: a distant celestial pointer

[Martin Meredith]

Corona Borealis is teeming with galaxies, though very few are bright, and the 223rd member of Shakhbazian's catalogue of compact galaxy groups is no exception. The brightest galaxy in this 14-strong grouping is mag 16.8B, but most are in the 18-19 range. I find the various configurations the compact galaxy groups make really interesting, but what makes Shakhbazian groups intriguing is their existence on the edge of what is plotted on deep charts, so it can be a surprise to see how they reveal themselves. 

Apart from gusts and some thin high cloud, conditions last night were very good, skies reaching SQM 20.64 and with a temperature of 20C even at midnight following 30+ during the day (not normal for May here). 

Here's a stack of 10 x 30s taken with the Lodestar X2 mono. What stands out in SHK 223 is the arrow-like grouping pointing at the pair of stars in the centre of the image, or perhaps indicating the other interesting zigzag grouping oriented vertically just below that pair. The vertex at the other end of the line from the arrowhead is actually a star and the galactic zigzag may be in part an illusion too: the chart below suggests that the middle pair of members are faint stars, and they do lack the halos characteristic of galaxies. (Incidentally, the halos are much more apparent when using LodestarLive's nonlinear modes. I hadn't anticipated how valuable these modes would be in separating small faint galaxies and stars). 

Here's an inverted, rotated (N at top) and 2x zoomed version along with a chart showing identifications. Its evident from the chart that the arrow and the zigzag, along with many of the other galaxies in the shot, are part of a larger cluster at around 1.2 BLY. 

The group can be found centred on 15h 49' 50.3" +29deg 8' 57.1", not too far from iota CrB.

Thanks for looking

Martin

[michael.h.f.wilkinson]

Nice one again

[JimStanley]

Great images Martin, thanks

Jim