January 2016 - Galaxy of the Month
NGC 2513 Group in Cancer and Canis Minor
NGC 2513 on the Cancer/Canis Minor border is the brightest galaxy in a small group. First discovered by William Herschel in 1786 NGC 2513 shines at about 12th magnitude. To its west are two much fainter NGC galaxies first found by Bindon Stoney in 1851 using Lord Rosse’s 72” telescope and catalogued as NGC 2510 and 2511.
These are all part of a poor galaxy group catalogued as WBL 169. The only other galaxy in the group with a common number is the nearby edge on spiral UGC 04171. The WBL catalogue however lists 9 galaxies in this group but most of the others are not assigned names. They are probably the CGCG galaxies mentioned below. Steve Gottlieb with his 17.5” saw 5 galaxies in the area surrounding NGC 2513.
The three NGC galaxies appear to be either elliptical galaxies or lenticulars, although NGC 2511 may be a spiral. Two of the others in the group which have assigned types appear to be spirals. The core trio of 2510, 2511 and 2513 was included in Miles Paul’s atlas of galaxy trios (available from the Webb Society) and has in fact featured in DSO 134 in an article on galaxy trios by Al Lamperti.
Detailed kinematic studies of NGC 2513 suggest it may be a triaxial spheroid from the motions of its stars. The group is thought to lie at a distance of about 200 million light years from us. The other galaxies in the group are probably CGCG 59-19, CGCG 59-21 CGCG 59-26, CGCG 59-27 along with UGC 04171.
As UGC 04171 is an edge on spiral this is likely to be quite difficult to observe so the best candidates outside the NGC galaxies are probably going to be 59-19 and 59-27. Neither of these will be easy and will probably need a large telescope from a very dark site to find.
The whole group should fit in medium power eyepiece field but the presence of an 8th magnitude star in the same field may make them a little harder to find. I was surprised to find that the group has not made any of the standard references such as the Night Sky Observer's Guide (NSOG). It is likely that an aperture of 40cm or greater will be required to see the main trio and perhaps 50cm+ to see the others, certainly if you are not working from high altitude skies.
The group is also part of the Astronomical League’s galaxy cluster list so should perhaps be better known than it appears to be.
Owen Brazell - Galaxy Section Director