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

Autori
Sabater, J. ; Best, P. N. ; Tasse, C. ; Hardcastle, M. J. ; Shimwell, T. W. ; Nisbet, D. ; Jelic, Vibor ; Callingham, J. R. ; Röttgering, H. J. A. ; Bonato, M. ; Bondi, M. ; Ciardi, B. ; Cochrane, R. K. ; Jarvis, M. J. ; Kondapally, R. ; Koopmans, L. V. E. ; O’Sullivan, S. P. ; Prandoni, I. ; Schwarz, D. J. ; Smith, D. J. B. ; Wang, L. ; Williams, W. L. ; Zaroubi, S.

Izvornik
Astronomy & astrophysics (Berlin) (0004-6361) 648 (2021); A2, 21

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
surveys ; catalogs ; radio continuum: general ; radio continuum: galaxies

Sažetak
The LOFAR Two-metre Sky Survey (LoTSS) will cover the full northern sky and, additionally, aims to observe the LoTSS deep fields to a noise level of ≲10 μJy beam−1 over several tens of square degrees in areas that have the most extensive ancillary data. This paper presents the ELAIS-N1 deep field, the deepest of the LoTSS deep fields to date. With an effective observing time of 163.7 h, it reaches a root mean square noise level of ≲20 μJy beam−1 in the central region (and below 30 μJy beam−1 over 10 square degrees). The resolution is ~6 arcsecs and 84 862 radio sources were detected in the full area (68 square degrees) with 74 127 sources in the highest quality area at less than 3 degrees from the pointing centre. The observation reaches a sky density of more than 5000 sources per square degree in the central region (~5 square degrees). We present the calibration procedure, which addresses the special configuration of some observations and the extended bandwidth covered (115-177 MHz ; central frequency 146.2 MHz) compared to standard LoTSS. We also describe the methods used to calibrate the flux density scale using cross-matching with sources detected by other radio surveys in the literature. We find the flux density uncertainty related to the flux density scale to be ~6.5 per cent. By studying the variations of the flux density measurements between different epochs, we show that relative flux density calibration is reliable out to about a 3 degree radius, but that additional flux density uncertainty is present for all sources at about the 3 per cent level ; this is likely to be associated with residual calibration errors, and is shown to be more significant in datasets with poorer ionosphere conditions. We also provide intra-band spectral indices, which can be useful to detect sources with unusual spectral properties. The final uncertainty in the flux densities is estimated to be ~10 per cent for ELAIS-N1.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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