Speaker
Description
We present the deepest sub-arcsecond wide-field image with LOFAR, obtained with 32 hours of international LOFAR data of the ELAIS-N1 deep-field. This image reveals structures of various astronomical objects with a resolution that surpasses the LOFAR Two-metre Sky Survey (LoTSS) (Shimwell et al. 2017, 2022) and the LoTSS-deep fields (Sabater et al. 2021; Kondapally 2021) by a factor 20. We obtain a best sensitivity of 14 μJy/beam with about 16 times less total observing time than what would be required for the same depth using solely the Dutch high-band antennas from LOFAR (Shimwell et al. in prep).
LoTSS already provides us with wide-field images of almost the complete northern sky at 144 MHz and 6” resolutions, revealing up to 5 million objects (Shimwell et al. 2022). However, 90% of the radio sources at 6” remain unresolved at these frequencies, prompting the need for higher resolutions. To address this, we have built upon the work from Morabito et al. (2022) and Sweijen et al. (2022), by improving the workflow for wide-field imaging incorporating international LOFAR data. Our focus was in particular on refining the DI calibration and automating the selection and calibration of direction-dependent calibrators. This effort resulted in three wide-field images at 0.3”, 0.6”, and 1.2” resolutions, which enables comparisons of source detections across resolution and sensitivity.
Beyond the extensive scientific output that can be derived from our deep sub-arcsecond wide-field image of ELAIS-N1, will our efforts also advance us toward the development of a robust and fully automated LOFAR VLBI pipeline. This pipeline is essential for efficiently processing upcoming sub-arcsecond northern sky surveys, facilitating the study of the low-frequency universe at the smallest angular scales.
