The MAVERIC survey: a catalogue of radio sources in southern globular clusters from the Australia Telescope Compact Array

Abstract

Radio continuum observations offer a new window on compact objects in globular clusters compared to typical X-ray or optical studies. As part of the MAVERIC surv e y, we hav e used the Australia Telescope Compact Array to carry out a deep (median central noise level ≈4 μJy beam -1 ) radio continuum surv e y of 26 southern globular clusters at central frequencies of 5.5 and 9.0 GHz. This paper presents a catalogue of 1285 radio continuum sources in the fields of these 26 clusters. Considering the surface density of background sources, we find significant evidence for a population of radio sources in seven of the 26 clusters, and also identify at least 11 pre viously kno wn compact objects (six pulsars and five X-ray binaries). While the overall density of radio continuum sources with 7.25-GHz flux densities 20 μJy in typical globular clusters is relatively low, the surv e y has already led to the disco v ery of sev eral e xciting compact binaries, including a candidate ultracompact black hole X-ray binary in 47 Tuc. Many of the unclassified radio sources near the centres of the clusters are likely to be true cluster sources, and multiwavelength follow-up will be necessary to classify these objects and better understand the demographics of accreting compact binaries in globular clusters.