Fast Radio Bursts: unveiling their local environments via high-resolution images

Fast Radio Bursts (FRBs) are millisecond duration, extremely luminous bursts detected at radio frequencies. Hundreds of FRBs have been detected to date, since their discovery fifteen years ago, but their nature still remains unclear. To be able to clearly identify the systems associated to the production of FRBs, it is critical to determine the local environments where FRBs occur. Due to the large distances to these extragalactic sources, we need a large number of very precise localizations that can only be carried out with very long baseline interferometric (VLBI) observations. We have been conducting VLBI observations during the last years to unveil the local environments of FRBs with the European VLBI Network (EVN), currently the only instrument capable of localizing FRBs down to the milliarcsecond level. This level of precision was critical to associate the first localized FRB, 20121102A, to the inside of a low-metallicity star-forming region in a dwarf galaxy and physically related it to a compact (< 0.7 pc) persistent radio source (Chatterjee et al. 2017; Marcote et al. 2017; Tendulkar et al. 2017), and a second repeating FRB, 20180916B, to just outside the edge of a prominent star-forming region of a nearby spiral galaxy (Marcote et al. 2020). Within the PRECISE project (Pinpointing REpeating ChIme Sources with EVN dishes) we keep a monitoring of repeating FRBs on a regular basis. PRECISE aims to push these localizations to a new level: localizing tens of these FRBs with milliarcsecond accuracy, with the ultimate goal of disentangling the environments where FRBs can be produced via statistical studies of the common properties observed in different FRBs. In this talk I will make a review on FRBs and the current state of the art of this field, discuss the importance of milliarcsecond localizations, the PRECISE project, and the localizations achieved until now, which have unveiled a variety of environments where FRBs can be found that challenges multiple models, including the localization of FRB 20200120E in a completely unexpected environment: the inside of a globular cluster in M81 (Kirsten, Marcote, et al. 2022)