Figure 9. Bottom Left: The Hubble Deep Field, taken in the optical waveband.

Inset, top left: A composite image of a small area showing optical emission (in false colour) overlaid by contours of radio intensity. The radio image was made with a combination of MERLIN (including the LT) and the VLA at a wavelength of 20cm. It is the most sensitive such image ever made. In this case, the radio source is extended in the same direction as the parent galaxy. It is almost certainly a starburst system similar to, but more luminous than, M82.

Inset, top right: Here the radio source is not coincident with an optical galaxy in the Hubble image. Recent infrared imaging at the position of the extended MERLIN+VLA radio source shows an object whose spectrum rises sharply into the infrared. This combination of properties strongly suggests that this is a dust-enshrouded galaxy at a redshift greater than 3.

Inset, bottom right: A radio source in the field-of-view of MERLIN but just outside the HDF. Its twin-jet shape is characteristic of sources powered by a central massive black-hole.