'Double Boomerang' Galaxy PKS 2014−55 | South Africa's MeerKAT Radio Telescope

'Double Boomerang' Galaxy PKS 2014−55 | South Africa's MeerKAT Radio Telescope

The detail provided in this radio image obtained with the MeerKAT telescope indicates that this galaxy's shape is best described as a ‘double boomerang’. Two powerful jets of radio waves, indicated in blue color, each extend 2.5 million light years into space (comparable to the distance between the Milky Way and the Andromeda galaxy, our nearest major neighbor). Eventually, they are ‘turned back’ by the pressure of tenuous intergalactic gas. As they flow back towards the central galaxy, they are deflected by its relatively high gas pressure into the shorter, horizontal, arms of the boomerang. The background image shows visible light from myriad galaxies in the distant universe. 

Annotated image showing X-shaped giant radio galaxy PKS 2014-55, observed with the South African Radio Astronomy Observatory’s MeerKAT telescope, indicating the old X-shaped radio jets, the younger jets closer to the central black hole, and the region of influence dominated by the central galaxy’s stars and gas. The curved arrows denote the direction of the backflow that forms the horizontal components of the X.

PKS 2014−55 is a Seyfert 2 elliptical galaxy presenting strong emission lines. It is an X-shaped radio galaxy discovered by the MeerKAT radio telescope in South Africa that is located 800 million light-years away from Earth. A radio galaxy is a galaxy with giant regions of radio emission extending well beyond its visible structure. These energetic radio lobes are powered by jets from its active galactic nucleus. This galaxy has jets extending 2.5 million light years across. Then the jets are “reversed” by the pressure of intergalactic gas, later deflected by gas pressure to form an “X” shape.

Many galaxies far more active than the Milky Way have enormous twin jets of radio waves extending far into intergalactic space. Normally, these go in opposite directions, coming from a massive black hole at the center of the galaxy. However, a few are more complicated and appear to have four jets forming an ‘X’ on the sky.

Several possible explanations have been proposed to understand this phenomenon. These include changes in the direction of spin of the black hole at the centre of the galaxy, and associated jets, over millions of years; two black holes each associated with a pair of jets; and material falling back into the galaxy being deflected into different directions forming the other two arms of the ‘X’. MeerKAT observations of one such galaxy, PKS 2014-55, strongly favor the latter explanation as they show material “turning the corner” as it flows back towards the host galaxy.

This work was carried out by a team from the South African Radio Astronomy Observatory (SARAO), the (US) National Radio Astronomy Observatory (NRAO), the University of Pretoria, and Rhodes University.

Previous studies of these unusual galaxies lacked the high quality imaging provided by the MeerKAT telescope. This telescope array consists of 64 radio dishes located in the Karoo semi-desert in the Northern Cape province of South Africa. Computers combined the data from these antennas into a telescope 8 km in diameter, and provided images in the radio band of unprecedented quality for PKS 2014-55 which enabled solving the mystery of its shape. 

The South African Radio Astronomy Observatory (SARAO), a facility of the National Research Foundation, is responsible for managing all radio astronomy initiatives and facilities in South Africa, including the MeerKAT radio telescope in the Karoo, and the geodesy and VLBI activities at the HartRAO facility. 

Learn more about MeerKAT: https://www.sarao.ac.za/science/meerkat/

Image Credit: South African Radio Astronomy Observatory (SARAO)/NRAO/AUI/NSF/DES
Release Date: May 7, 2020

#NASA #Astronomy #Space #Science #Stars #Galaxies #EllipticalGalaxies #PKS201455 #BlackHoles #TelescopiumConstellation #Cosmos #Universe #MeerKATRadioTelescope #RadioAstronomy #SARAO #SouthAfrica #NRAO #AUI #NSF #DES #UnitedStates #STEM #Education