The LOFAR LBA Sky Survey II. First data release

Abstract

The Low Frequency Array (LOFAR) is the only existing radio interferometer able to observe at ultra-low frequencies (<100 MHz) with high resolution (<15") and high sensitivity (<1 mJy/beam). To exploit these capabilities, the LOFAR Surveys Key Science Project is using the LOFAR Low Band Antenna (LBA) to carry out a sensitive wide-area survey at 41-66 MHz named the LOFAR LBA Sky Survey (LoLSS). LoLSS is covering the whole northern sky above declination 24 deg with a resolution of 15" and a sensitivity of 1-2 mJy/beam (1 sigma) depending on declination, field properties, and observing conditions. Here we present the first data release. An automated pipeline was used to reduce the 95 fields included in this data release. The data reduction procedures developed for this project have general application and are currently being used to process LOFAR LBA interferometric observations. Compared to the preliminary release, direction-dependent errors have been corrected for during the calibration process. This results in a typical sensitivity of 1.55 mJy/beam at the target resolution of 15". The first data release of the LOFAR LBA Sky Survey covers 650 sqdeg in the HETDEX spring field. The resultant data products released to the community include mosaic images (I and V Stokes) of the region, and a catalogue of 42463 detected sources and related Gaussian components used to describe sources' morphologies. Separate catalogues for 6 in-band frequencies are also released. The first data release of LoLSS shows that, despite the influences of the ionosphere, LOFAR can conduct large-scale surveys in the frequency window 42-66 MHz with unprecedentedly high sensitivity and resolution. The data can be used to derive unique information on the low-frequency spectral properties of many thousands of sources with a wide range of applications in extragalactic and galactic astronomy.

20 pages, 22 figures, images and catalogues available at https://www.lofar-surveys.org/lolss.html

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• Limits and challenges of the detection of cluster-scale diffuse radio emission at high redshift: The Massive and Distant Clusters of WISE Survey (MaDCoWS) in LoTSS-DR2
• Cosmic dance in the Shapley Concentration Core II. The uGMRT-MeerKAT view of filaments in the brightest cluster galaxies and tailed radio galaxies in the A3528 cluster complex
• Finding AGN remnant candidates based on radio morphology with machine learning
• Comparing extragalactic megahertz-peaked spectrum and gigahertz-peaked spectrum sources
• Probing particle acceleration in Abell 2256: from to 16 MHz to gamma rays
• Characterization of the decametre sky at subarcminute resolution
• No strong radio absorption detected in the low-frequency spectra of radio-loud quasars at z > 5.6
• Radio-only and Radio-to-far-ultraviolet Spectral Energy Distribution Modeling of 14 ULIRGs: Insights into the Global Properties of Infrared Bright Galaxies
• Matching LOFAR sources across radio bands
• Apertif 1.4 GHz continuum observations of the Boötes field and their combined view with LOFAR
• A 100 kpc Ram Pressure Tail Trailing the Group Galaxy NGC 2276
• Robust direction-dependent gain-calibration of beam-modelling errors far from the target field
• Searching for Radio Transients with Inverted Spectra in Epoch 1 of VLASS and VCSS, and Identification of a Sample of Candidate Relativistic Nuclear Transients
• Non-thermal emission in galaxy groups at extremely low frequency: the case of A1213
• A Giant Metrewave Radio Telescope Survey of Radio-loud Broad Absorption Line Quasars
• The LOFAR sub-arcsecond view of the high-redshift radio relic in PSZ2G091.83+26.11
• LOFAR 58 MHz Legacy Survey of the 3CRR Catalog
• Minimum Energies and Magnetic Field Strengths of Edge-brightened Compact Symmetric Objects
• Pulsars identified in the LOFAR Two-metre Sky Survey at 144 MHz
• The evolution of extragalactic peaked-spectrum sources down to 54 megahertz
• Multi-wavelength insights into the pulsar wind nebula candidate near 1LHAASO J0343+5254u: an obscured merging galaxy cluster?
• Single- and double-headed odd radio circles in the LOFAR surveys