The LOFAR Two-meter Sky Survey: Deep Fields Data Release 1

The LOFAR Two-metre Sky Survey (LoTSS) will cover the full northern sky and, additionally, aims to observe LoTSS deep fields a noise level of ~10 microJy/bm over several tens square degrees in areas that have most extensive ancillary data. This paper presents ELAIS-N1 field, deepest date. With an effective observing time 163.7 hours, it reaches root mean (RMS) below 20 central region (and 30 10 degrees). resolution is 6 arcsecs and 84862 radio sources were detected area (68 sq. deg.) with 74127 highest quality at less than 3 from pointing centre. observation density more 5000 per deg. ~5 region. We present calibration procedure, which addresses special configuration some observations extended bandwidth covered (115 177 MHz; frequency 146.2 MHz) compared standard LoTSS. also describe methods used calibrate flux scale using cross-matching by other surveys literature. find uncertainty related be ~6.5%. By studying variations measurements between different epochs, we show relative reliable out about degree radius, but additional for all cent level; this likely associated residual errors, shown significant datasets poorer ionosphere conditions. provide intra-band spectral indices, can useful detect unusual properties. final densities estimated ~10% ELAIS-N1.