Research

The International LOFAR Telescope can combine stations across Europe, allowing us to create radio images of 2.5° × 2.5° field of views at sub-arcsecond resolution and at frequencies below 200 MHz. Accurately calibrating and imaging the visibility data corresponding to LOFAR's long baselines is challenging and requires a lot of computing power. I co-develop scalable data-reduction strategies and techniques that automate LOFAR processing for wide-field imaging, so it runs efficiently on high-performance computing clusters. The goal is to survey large areas of the sky and eventually the entire northern sky.

By combining multiple LOFAR observations, we can produce deep high-resolution images at low frequencies. I produced LOFAR's deepest sub-arcsecond wide-field images of ELAIS-N1 and the Euclid Deep Field North, and developed sidereal visibility averaging, which gives a significant imaging speed-up (up to an order of magnitude), by averaging visibilities for similar baselines coordinates. Ultimately, the aim is to push to deeper and deeper imaging during the LOFAR2.0 era, since LOFAR, with its long baselines, is currently the only radio telescope capable of overcoming confusion noise far below 10 µJy/beam and at the lowest frequencies. This will allow us to study the faintest and most distant radio sources and their cosmic evolution up to the highest redshifts.

Using total intensity (Stokes I) radio emission detected by LOFAR, I studied the well-known pre-merging galaxy cluster pair Abell 399–401. By combining multiple LOFAR observations, I imaged the radio bridge connecting the two clusters to investigate the re-acceleration mechanism that drives the radio emission. At smaller scales, I also compared the redshift evolution of two distinct radio galaxy morphologies (FRI and FRII) across a wide area across the northern sky. Our results suggest that radio jets may be disrupted mainly by processes within the host galaxy rather than by the larger-scale environment, although higher resolution and larger samples are needed to draw firmer conclusions. I am now also studying polarised emission from radio galaxies, using new calibration techniques that enable wide-field polarimetry at LOFAR's highest resolution.