# Extragalactic radio surveys in the pre-Square Kilometre Array era

## TL;DR

This paper reviews six decades of extragalactic radio surveys, discusses their relationship with multi-wavelength data, and outlines future prospects in the era of the Square Kilometre Array.

## Contribution

It provides a comprehensive summary of past radio surveys, current knowledge, and future directions in extragalactic radio astronomy before the SKA era.

## Key findings

- Decades of radio surveys have significantly advanced understanding of extragalactic sources.
- Multi-wavelength observations are crucial for comprehensive insights.
- Future prospects include new questions and opportunities with upcoming SKA data.

## Abstract

The era of the Square Kilometre Array is almost upon us, and pathfinder telescopes are already in operation. This brief review summarizes our current knowledge of extragalactic radio sources, accumulated through six decades of continuum surveys at the low-frequency end of the electromagnetic spectrum and the extensive complementary observations at other wavelengths necessary to gain this understanding. The relationships between radio survey data and surveys at other wavelengths are discussed. Some of the outstanding questions are identified and prospects over the next few years are outlined.