The highest resolution at the lowest frequencies: what LOFAR can tell us about AGN

Leah Morabito (Durham)

The International LOFAR Telescope (ILT) has baselines up to 2,000 km, making it capable of achieving sub-arcsecond resolution at frequencies below 200 MHz. This makes it an incredible instrument for studying active galactic nuclei (AGN), both in terms of unique statistical studies and detailed studies of individual sources. However, high resolution imaging at low frequencies is technically and logistically challenging: the ILT's phased-array design, the ionosphere, the lack of suitable calibrator information, and existing software tools all conspire to make it difficult to achieve the highest possible resolution at MHz frequencies. Over the past few years, we have built on our growing understanding of these challenges to design a suitable calibration strategy, which is now implemented in a publicly available pipeline. In the past year this has enabled us to more than double the number of scientific papers published using sub-arcsecond imaging < 200 MHz, including cutting edge work to image the entire 5 square degree field of view of the ILT at sub-arcsecond resolution. I will provide an overview of how we overcome these challenges and then focus on examples of our breakthrough successes and recent science results. I will focus particularly on how we can use this unique combination of resolution, frequency, and field of view to diagnose the radio emission in galaxies and understand the radio emission mechanisms in radio quiet AGN, which is a major open question. I will finish by providing an overview on current and future plans, including a Northen sky survey which will have higher resolution than any previous wide-area radio survey.