NGC 7463 in Pegasus
September 2021 - Galaxy of the Month
Our target this month is the tight triplet of galaxies around NGC 7463 in Pegasus. NGC 7643 itself was discovered by William Herschel in 1784 along with the other brightish galaxy in the group, NGC 7465. The other galaxy in the triplet, NGC 7464, was discovered by d’Arrest in 1864, although it was independently rediscovered by Marth and Vogel later that year.
The WBL has it as part of a small galaxy group listed as WBL 695 which includes the 3 NGC galaxies and UGC 12321. The faint edge on spiral UGC 12313 nearby is not listed as part of the group, however HI observations suggest that it may be connected with the others.
NGC 7463 itself appears to be a barred spiral galaxy with the outer spiral arms distorted by interactions, possibly with NGC 7464. NGC 7464 is itself an interesting system as it is classified as E1pec, although its colours are very blue and it shows emission lines. There are other morphological classifications which suggest it maybe an irregular galaxy however. The NGC 7463/7464 group is also known as Holmberg 802.
The third galaxy in the trio, NGC 7465, is also classified as a distorted form of a barred spiral. The nucleus of NGC 7465 seems to be a LINER, a mild form of AGN and the galaxy contains a lot of dust. It has also been classified as a Seyfert 2 type system. It appears to have a ring of star formation, or a shell of material which may come from interactions within the system or from a merger in the past. It could perhaps also be a polar ring galaxy. The core of the NGC 7465 also appears to have some intense star forming going on.
The main interactions in the group appear to be currently between NGC 7464 and NGC 7465. Interestingly the Lyons Groups of Galaxies (LGG) has NGC 7465 and 7464 as part of the NGC 7448 group as LGG 469. NGC 7463 is not part of that group.
The group is fairly small and faint and thus it is of interest that the Night Sky Observer's Guide (NSOG) Vol 1 suggests it as a target for 12/14 inch telescopes. It does not appear in Luginbuhl and Skiff (L&S). Steve Gottlieb suggests that even in a 18” telescope NGC 7464 was faint. The group is very tight and as such is probably going to require high magnification in order to be able to split all the components, in the range I would think of 250-350x.
Owners of large telescopes may also be able to pick up the two UGC galaxies associated with the core trio, although I expect finding these may require the most transparent nights, although Steve Gottlieb reports that they are faint even in Texas skies with a 48”.
Owen Brazell - Galaxy Section Director