NGC 541

Lore & Background

NGC 541 was discovered by Heinrich d'Arrest on October 30, 1864. It is a radio galaxy of Fanaroff–Riley class I, also designated 3C 40A; the more prominent 3C 40B is associated with the nearby galaxy NGC 547. Observations by the Hubble Space Telescope revealed a central disk seen nearly face-on with a diameter of 1.8 arcseconds, containing an inner ring about 0.44 arcseconds across that may be part of a faint spiral structure. A linear dust feature protrudes from the disk, aligned nearly with the radio jet. H-alpha and [N II] emission peaks at the center of the dust disk and forms a ring around the peak with two brighter diametrically opposed spots. CO emission observations indicate the presence of molecular gas with an estimated mass of approximately 10^8 solar masses, distributed in a compact ring-like structure with a radius of 1–2 kiloparsecs. At the galaxy's center lies a supermassive black hole with a mass estimated between 1.9 × 10^8 and 9.2 × 10^8 solar masses.

Reader's Guide

NGC 541's significance lies in its role as a radio galaxy whose jet has directly triggered star formation in a nearby dwarf irregular galaxy, Minkowski's object, located 45 arcseconds to the northeast. Strong evidence indicates that the radio jet of NGC 541 caused a starburst in Minkowski's object, where at least 20 regions with star clusters and associated HII regions have been detected. The stellar population there is dominated by stars formed in a single event 7.5 million years ago, with a current star formation rate of 0.52 solar masses per year. While it has been proposed that Minkowski's object was a dwarf galaxy that passed through the jet, it is more probable that the HI region was warm intergalactic gas cooled by the jet, a model reproduced by computer simulations. A stellar bridge has been detected between NGC 541 and the galaxy pair NGC 545/547, located 4.5 arcminutes to the northeast. Two supernovae have been observed near NGC 541: SN 2010ib (Type II, magnitude 19.2) thought to be associated with Minkowski's object, and SN 2018ctv (Type Ia, magnitude 17.2) located about halfway between NGC 541 and NGC 545, so it could be associated with either galaxy.

Did You Know?

• NGC 541 is a Fanaroff–Riley class I radio galaxy also known as 3C 40A.
• Its radio jet is thought to have triggered a starburst in the nearby dwarf galaxy Minkowski's object.
• The supermassive black hole at its center has an estimated mass between 1.9 and 9.2 × 10^8 solar masses.
• A stellar bridge connects NGC 541 to the galaxy pair NGC 545/547.