Radio Continuum surveys have been conducted since the earliest days of radio astronomy, at the time of Karl Jansky: These surveys of the sky in radio frequencies give astronomers an understanding of the distribution and intensity of radio sources across the sky.
The resolution of the radio survey telescopes determines how much detail can be seen in these surveys, from basic things like the galactic centre, the plane of our own galaxy the Milky Way, or individual radio sources such as distant galaxies or pulsars.
The earliest continuum survey results were most likely obtained by Grote Reber in the 1940s when, following on from the pioneering work of Jansky a decade earlier, he managed to map the radio sky at 160Mhz, taking in the major emission regions in Sagittarius, Cygnus and Cassiopeia
The SKA’s role
Sky Surveys in the radio with the SKA will allow astronomers to catalogue the millions of radio sources across the sky faster than ever before. They will lead to the detection of transient events that can then be followed up by more targeted observations.
The SKA’s angular resolution and survey speed capability, exceeding current survey speeds by thousands of times, will mean that continuum surveys of the Southern Hemisphere will be more detailed than ever before.
In the next decade prior to the SKA being finalised however, several next-generation radio telescopes and upgrades to existing telescopes are already performing these sky surveys from all around the world.
These include APERTIF (The Netherlands), ASKAP (Australia), eMERLIN (UK), VLA (USA), e-EVN (based in Europe), LOFAR (The Netherlands), Meerkat (South Africa), and the Murchison Widefield Array (MWA).
A radio continuum survey is being planned on each of them with the primary science objective of understanding the formation and evolution of galaxies over cosmic time, and the cosmological parameters and large-scale structures which drive it.
As part of the ongoing research which will lead up to the full operations of the SKA, the different teams working on this wide range of telescopes are developing a variety of new techniques, and refining existing ones to enable continuum survey capabilities with the SKA, the like of which have never been seen before.