New results from the low-frequency counterpart of the XMM large scale structure survey

Abstract

The XMM Large Scale Structure survey (XMM-LSS) is an X-ray survey aimed at studying the large scale structure of the Universe. The XMM-LSS field is currently being followed up using observations across a wide range of wavelengths, and in this paper we present the observational results of a low frequency radio survey of the XMM-LSS field using the Very Large Array at 74 and 325 MHz. This survey will map out the locations of the extragalactic radio sources relative to the large scale structure as traced by the X-ray emission. This is of particular interest because radio galaxies and radio loud AGN show strong and complex interactions with their small and larger scale environment, and different classes of radio galaxies are suggested to lie at different places with respect to the large scale structure. For the phase calibration of the radio data, we used standard self-calibration at 325 MHz and field-base calibration at 74 MHz. Polyhedron-based imaging as well as mosaicing methods were used at both frequencies. At 74 MHz we have a resolution of $30''$, a median $5\sigma$ sensitivity of $\sim162$ mJy/beam and we detect 666 sources over an area of 132 square degrees. At 325 MHz, we have a resolution of $6.7''$, a median $5\sigma$ sensitivity of 4 mJy/beam, and we detect 847 sources over an area of 15.3 square degrees. At 325 MHz we have detected a region of diffuse radio emission which is a cluster halo or relic candidate.