PKS 0634-20 | |
---|---|
![]() The radio galaxy PKS 0634-20. | |
Observation data (J2000 epoch) | |
Constellation | Canis Major |
Right ascension | 06h 36m 32.25s [1] |
Declination | −20° 34′ 53.14″ [1] |
Redshift | 0.056456 [1] |
Heliocentric radial velocity | 16,925 km/s [1] |
Distance | 753 Mly |
Apparent magnitude (V) | 17.58 |
Apparent magnitude (B) | 18.27 |
Characteristics | |
Type | E NLRG [1] |
Size | ~184,400 ly (56.53 kpc) (estimated) [1] |
Other designations | |
2MASX J06363227-2034532, IRAS 06343-2032, 6dF J0636323-203453, PGC 19313, PKS B0634-205, PKS J0636-2036, Cul 0634-205, 0634-20 [1] |
PKS 0634-20 is a powerful Fanaroff-Riley class Type II radio galaxy [2] located in the constellation of Canis Major. It has a redshift of (z) 0.056 [1] and was first discovered by astronomers who were conducting the Parkes catalogue survey at Parkes Observatory in 1964. [3] This object is also classified as a Type 2 Seyfert galaxy. [4]
PKS 0634-20 is classified as a giant radio galaxy with a complex radio structure. When imaged with a 21 centimeter radio map, the structure is best described as a double-triple made up of seven components with an unresolved southern bright component. [5] Observations made by the Westerbork Synthesis Radio Telescope found the outer edges of two components have a separation gap of 14 arcseconds. In addition, the components are narrow and configured, similar to 3C 236. [6]
Observations made with the Effelsberg 100-m Radio Telescope and Very Large Array, discovered there is a long radio emission bridge in PKS 0634-20. When imaged, the bridge is found extending to the outer collinear hotspots with its polarization degree varying from 8% to 30%. When travelling a far distance in terms of projection, there is a change in which the bridge becomes narrower and the polarization degree increases. Results also showed the hotspots located at north and south directions have polarization percentages of 5% and 20%. As mapping at 4".5 resolution also showed the same thing, this suggests either beam cancellation of the northern sub-parts of the hotspot or differential Faraday rotation. [7] Imaging at high resolutions by the Australia Telescope Compact Array also showed the south hotspot has a significant sub-structure. [8]
The host of PKS 0634-20 is a normal elliptical galaxy lying in the poor cluster environment. [2] [9] According to imaging by the Anglo-Australian Telescope, the appearance of the galaxy is described as peculiar with a sign of a filamentary structure showing an extension into a northwest quadrant. [10] There is an emission line nebula extending by 20 kiloparsecs from its central nucleus with molecular gas estimated to be 3 x 109 Mʘ. As its mass is greater than the warm gas in the galaxy, this indicates the nebula is radiation-bound. The large quantity of gas is believed to be acquired from either a spiral or a gas-rich galaxy. [11]
Strong doubly ionized oxygen narrow emission lines has been identified in the spectra of PKS 0634-20 with an extent of 70 kiloparsecs along its radio axis. [10] Astronomers also suggested the galaxy might have a hidden quasar based on the discovery of a reddened source coinciding with its nucleus. [12]