Radio Observations of the 13hr XMM/ROSAT Deep X-ray Survey Area

In order to determine the relationship between the faint X-ray and faint radio source populations, and hence to help understand the X-ray and radio emission mechanisms in those faint source populations, we have made a deep 1.4GHz Very Large Array radio survey of the 13 +38 XMM/ROSAT X-ray Survey Area. From a combined data set of 10hours B configuration data and 14hours A configuration data, maps with 3.35 resolution and a noise limit of 7.5μJy were constructed. A complete sample of 449 sources was detected within a 30 diameter region above a 4σ detection limit of 30μJy, at the map centre, making this one of the deepest radio surveys at this frequency. The differential source count shows a significant upturn at sub-milliJansky flux densities, similar to that seen in other deep surveys at 1.4GHz (e.g. the Phoenix survey), but larger than that seen in the HDF which may have been selected to be under-dense. This upturn is well modelled by the emergence of a population of medium redshift starforming galaxies which dominate at faint flux densities. The brighter source counts are well modelled by AGNs.