NGC 4410A in Virgo
April 2020 - Galaxy of the Month
This month’s challenge is the interacting group of galaxies around NGC 4410A. The main double galaxy NGC 4410 was discovered by John Herschel in 1828. Although the group has been listed as part of the Virgo cluster and lies within its spatial bounds on the sky it actually lies at a distance of perhaps 111 Mpc, far beyond the Virgo cluster. The other galaxies in the group include IC 790, sometimes called NGC 4410C, and PGC 40736, sometimes known as NGC 4410D. The galaxies are all interacting and show tidal tails.
The group is also listed as WBL 408, a group of 9 galaxies which also includes NGC 4411. However there are some issues with this as some distance measurements place NGC 4411 at about 55 million light years so it would be part of the Virgo cluster not part of the 4410 group. Note that NGC 4411 is also known as IC 3339 because there were errors in the co-ordinates listed by the discoverers Bigourdan and Peters, and Dreyer thought they were two separate objects.
The galaxy PGC 40745, sometimes known as NGC 4411B may be associated with NGC 4411A and thus part of the Virgo cluster.
There is an excellent image of the group at Hanson Astronomy Photos and also at the Chilean Advanced Robotic Telescope website and a much deeper image at the Canada-France-Hawaii Telescope (CFHT) website. For an annotated image of all the galaxies in the area see the ManTrapSkies website.
The group contains some X-ray emitting gas which may be related to the active nucleus of NGC 4410A. It is suggested that the group is in the process of evolving from a spiral rich group, which typically do not have a hot intra cluster medium, to an elliptical one via mergers. The strong UV emission from the group also meant it made Markarians catalogue as Mrk 1325. Perhaps surprisingly it did not make Arp’s catalogue, although it is in the extended Vorontsov-Velyaminov (VV) catalogue of interacting galaxies as VV 1537.
Observationally there are a number of galaxies that may be picked up in the area. At the recent (2020) Haw Wood Star Party I saw 5 galaxies in the area using my 22-inch but others using smaller telescopes saw 7. This may come from using a tablet program such as SkySafari at the telescope when you know there are other galaxies there and look for them rather than looking cold at the field. It also helps to have a driven scope that stops wind buffeting. To show that NGC 4410 is a double galaxy may require high power.
NGC 4411a and b are face on spirals and are large and diffuse and as such much more difficult to see, they will however appear in the same field as NGC 4410 when using a modern hyperwide eyepiece at say 250x.
Owen Brazell - Galaxy Section Director