Circularly polarised LoTSS sources

We used the second data release of the 144MHz LOFAR Two-metre Sky Survey to prodce circularly polarised maps with a median noise of 140uJy/beam and resolution of 20-arcsec for 27% of the northern sky (5634deg^2^). The leakage of total intensity into circular polarisation is measured to be ~0.06%, and our survey is complete at flux densities >=1mJy.

A detection is considered reliable when the circularly polarised fraction exceeds 1%. We find the population of circularly polarised sources is composed of four distinct classes: stellar systems, pulsars, active galactic nuclei, and sources unidentified in the literature. The stellar systems can be further separated into chromospherically active stars, M dwarfs, and brown dwarfs.