NGC 315 in Pisces
August 2022 - Galaxy of the Month
For the August galaxy of the month I have chosen NGC 315 in Pisces. Although perhaps a bit early for galaxies in Pisces, we are still in Milky Way season. NGC 315 was discovered by William Herschel in 1784. It appears to be part of a small group on the sky that also contains NGC 311 and NGC 318.
NGC 315 contains an AGN, in this case a LINER, with a well collimated radio jet coming from the central black hole. The jet has also been detected in X-Rays. The jet appears as two main parts, a bright main jet and a smaller counter jet. The mass of the central black hole has been calculated to be of the order of 2x109 solar masses from observations of cold molecular gas around it using ALMA. The nucleus also shows up well in the UV images from the GALEX satellite.
There may be upwards of 30 galaxies in the group associated with NGC 315. NGC 315 is part of Zwicky cluster 0107.5+3212 (Zwicky et al. 1961), which is located in the Perseus-Pisces filament. It is also part of the group WBL 22 (which only contains NGC 311, NGC 315 and NGC 318) and LGG 14 (which contains many more). NGC 315 is classified as a cD elliptical galaxy; these are large elliptical galaxies found at the core of clusters. The group is thought to be at a distance of perhaps 55 Mpc. Most studies of this galaxy seem to concentrate on the jet.
Observationally NGC 315 is defined to be part of a trio of galaxies including NGC 311 and NGC 318. NGC 311 and 318 are much fainter than NGC 315. NGC 311 was discovered by John Herschel in 1828 and NGC 318 by Bindon Stoney using Lord Rosse’s 72” telescope in 1850. They both appear to be lenticular type systems. Stoney also thought he discovered another two galaxies in the field that got the NGC numbers NGC 313 and NGC 316 but it turns out these were just stars.
Night Sky Observer's Guide (NSOG) suggests that all three can be seen with a 35cm telescope, although NGC 318 is recorded as difficult to see. My suspicion however is that these observations were made from high altitude sites and from the UK it may require 40cm to see all three given the extra mile of crud above most UK observing sites. The group is a very tight one and will easily fit in a high power eyepiece field. Observations of the group maybe complicated by an 8th magnitude star close by in the field. NGC 315 is included as part of the Astronomical League H400 II list.
Owen Brazell - Galaxy Section Director